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DOI: 10.1148/radiol.2293021756
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(Radiology 2003;229:821-829.)
© RSNA, 2003

Vascular and Interventional Radiology

Unresectable Pulmonary Malignancies: CT-guided Percutaneous Radiofrequency Ablation—Preliminary Results1

Robert D. Suh, MD, Amanda B. Wallace, BS, Ramon E. Sheehan, MD, Stefan B. Heinze, MD and Jonathan G. Goldin, MD

1 From the Department of Radiological Sciences, UCLA Medical Center, 10833 Le Conte Ave, B2–168, Center for the Health Sciences (CHS), Los Angeles, CA 90095-1721. Received December 18, 2002; revision requested February 27, 2003; revision received May 23; accepted July 1. Address correspondence to R.D.S. (e-mail: rsuh@mednet.ucla.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To assess whether percutaneous radiofrequency (RF) ablation of unresectable pulmonary malignancies is safe and technically feasible and to evaluate the usefulness of computed tomographic (CT) nodule densitometry as a tool for following up tumors after ablation.

MATERIALS AND METHODS: Twelve patients (seven men and five women; mean age, 60.6 years) with unresectable disease (because of poor lung reserve or multifocality) underwent nodule CT densitometry and CT-guided percutaneous RF ablation of 19 lung tumors (six [32%] tumors were adenocarcinoma, one (5%) was large cell carcinoma, two (10%) were bronchoalveolar carcinoma, four (21%) were colorectal carcinoma, and six (32%) were sarcoma less than 50 cm2 in area (range, 0.25–35.00 cm2). No patients had symptoms of their disease before RF ablation. Follow-up CT densitometry was scheduled for 1, 3, 6, and 12 months after RF ablation. Lesions were evaluated for change in area and contrast enhancement at follow-up CT.

RESULTS: RF ablation was well tolerated by all patients. Intraprocedural complications included 12 cases of pneumothoraces (two patients required chest tube placement, while 10 were asymptomatic and required no further treatment), two cases of pleural effusion, and two cases of moderate pain (one case during and one case both during and after the procedure). Mean follow-up was 41/2 months (range, 1–12 months). In the eight patients with 3-month follow-up, lesion size increased in two and remained stable in six. Mean contrast enhancement, however, decreased from 46.8 HU (range, 19–107 HU) at baseline to 9.6 HU (range, 0–32 HU) at 1–2-month follow-up. In the one patient with 12-month CT densitometry follow-up, lesion enhancement was less than 50% of that at baseline, and lesion diameter remained stable.

CONCLUSION: These preliminary results show that percutaneous RF ablation is a safe and technically feasible management option for unresectable pulmonary malignancies. CT densitometry may have potential for future use as a noninvasive method of following up tumors after RF ablation.

© RSNA, 2003

Index terms: Lung, nodule, 60.3115 • Lung neoplasms, CT, 60.12115 • Lung neoplasms, therapy • Radiofrequency (RF) ablation


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Percutaneous radiofrequency (RF) ablation is a minimally invasive electrosurgical technique involves use of heat to produce tissue necrosis (1). RF ablation is well established as a treatment for various cardiac and neurologic conditions (2–7). Bipolar and multielectrode RF ablation probes capable of internal tip cooling have enabled the creation of larger areas of necrosis, thus expanding potential applications of RF ablation to include tumor therapy (1,8–10). Findings in other studies (11–18) indicate that RF ablation is a safe and effective technique for treating both primary and secondary hepatic and brain tumors. The use of RF ablation to treat lung malignancies, however, is less well studied.

As the leading cause of cancer death in the United States, lung cancer is a serious health care burden (19). Unfortunately, though complete recovery may be seen with early resection, approximately 15% of patients with pulmonary malignancies are surgical candidates (19–21). Most patients who are poor surgical candidates are in one of two categories: those with poor pulmonary reserve and those with widespread disease at diagnosis. In the first group, patients with lung cancer often have comorbid cardiopulmonary disease and therefore insufficient reserve to withstand lobectomy (20,22–23). Likewise, advanced disease is most often incurable surgically (20–21). While findings in studies show survival benefits after metastatectomy (24–28), surgery involves numerous risks that might be avoided with a less invasive intervention (20–21,29). Unfortunately, chemotherapy and external beam radiation have not greatly affected outcomes in patients with unresectable disease (19–20). RF ablation is a relatively new minimally invasive technique that may eventually provide these patients with a means of local control.

If RF ablation is to become widely used for treating lung tumors, a reliable imaging study for following up tumor regression is needed. Unfortunately, lesion size and morphology at conventional computed tomography (CT) may not always be useful indexes of ablation efficacy. Berber et al (30) reported difficulty in the interpretation of postablation CT scans of treated hepatic lesions because the appearance of ablated lesions surrounded by a rim of ablated normal liver tissue mimicked interval enlargement of the tumor. The use of nodule CT densitometry for following up solitary pulmonary nodules, however, has received considerable attention in the literature. This technique involves measurement of nodule enhancement after administration of intravenous contrast material and takes advantage of differences in vascularity and vasculature of benign and malignant lesions. Findings in a multicenter study by Swensen et al (31) showed 98% sensitivity in detection of malignancy if a threshold of 15-HU enhancement above baseline was used. Although the use of this technique to follow up tumors after RF ablation is less well studied, Berber et al (30) reported that successfully treated liver tumors decreased in enhancement after RF ablation. If the findings are found to be reliable, CT densitometry may eventually become a valuable index for following up lung tumors after RF ablation.

The purpose of our study was to assess whether percutaneous RF ablation of unresectable pulmonary malignancies is safe and technically feasible and to evaluate the usefulness of nodule CT densitometry as a tool for following up tumors after ablation.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patients and Tissue Diagnosis
Institutional review board approval was obtained for an 18-month prospective feasibility study between May 2000 and November 2001. Patients with primary or secondary intrathoracic malignancies (including intrapulmonary, mediastinal, and pleural or chest wall malignancies) less than 50 cm2 in area that were refractory to or not amenable to conventional therapies (surgery, chemotherapy, and radiation therapy) were eligible for participation. For the purposes of this study, patients with forced expiratory volume in 1 second, or FEV1, of less than 0.8 L were considered to be poor surgical candidates because of their limited pulmonary reserve. Criteria for exclusion from the study included lesions located less than 1 cm from major blood vessels or airways, which were believed to be inaccessible by the primary radiologist (R.D.S.); lesions with an international normalized ratio greater than 1.8; and lesions with a platelet count of less than 50 x 103/µL. All decisions to refer patients to our RF ablation program were made on the basis of recommendations by the Thoracic Oncology Tumor Board (a multidisciplinary group) after review of treatment options. Written informed consent was obtained from all patients after the risks and benefits of participation in the study were fully explained.

Ultimately, 12 patients (seven men and five women; mean age, 60.6 years; range, 44–71 years) who had no disease symptoms underwent RF ablation of 19 lung nodules. Male patients had a mean age of 62.7 years (range, 53–71 years), while female patients had a mean age of 57.6 years (range, 44–68 years). Eight of our patients had primary lung cancer, and four had metastatic disease. All 12 patients had disease that was believed to be unresectable because of poor pulmonary reserve or extent of disease. The clinical-pathologic characteristics of these patients and their tumors are summarized in Table 1. Nineteen treated lesions (those in one patient were excluded) were sampled at biopsy for tissue diagnosis before ablation: 32% (six lesions) were adenocarcinoma, 5% (one lesion) were large cell carcinoma, 10% (two lesions) were bronchoalveolar carcinoma, 32% (six lesions) were metastatic leiomyosarcoma, and 21% (four lesions) were metastatic colorectal carcinoma. Patient 4 did not undergo biopsy because the lesions were all smaller than 1 cm; however, these lesions were believed to be metastatic colorectal carcinoma on the basis of clinical findings.


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  		TABLE 1. Clinical Pathologic Characteristics of Patients Undergoing RF Ablation to Treat Pulmonary Malignancies

 
Imaging and Procedures
All procedures were performed by one radiologist (R.D.S.) with a first-generation spiral CT scanner (HighSpeed Spiral CT/I; GE Medical Systems, Milwaukee, Wis). CT fluoroscopy was not used in any case. Nodule CT densitometry was performed before placement of the RF ablation probe. After localization of the nodule on the preview, a limited thin-section baseline CT scan was obtained (with 3-mm collimation and pitch of 1:1) through the lesion. Dynamic contrast material–enhanced images were then obtained through the nodule at 45, 90, 180, and 300 seconds after intravenous injection of 100 mL of nonionic contrast material (iohexol, Omnipaque 350; Nycomed, New York, NY) at a rate of 2 mL/sec. All CT scans were read by the same radiologist. In addition, each CT scan was read independently by one of four other radiologists in our Department of Thoracic Imaging, for a total of two interpretations per scan. Nodule enhancement was calculated by subtracting precontrast nodule attenuation (in Hounsfield units) from maximum postcontrast nodule attenuation (in Hounsfield units) among all time points studied. Because tumors are often heterogeneous, attenuation was measured by placing the region of interest marker on the most solid, reproducible area of the lesion. Lesion size was measured in all patients and was reported as the largest bidimensional diameters at CT. Follow-up CT studies to measure lesion size and enhancement with the same CT scanner and imaging protocol were scheduled for 1, 3, 6, and 12 months after RF ablation. The product of the bidimensional lesion sizes was used to determine stability of lesion size on the basis of the World Health Organization criteria: Significant change was defined as greater than 25% increase or greater than 50% decrease in lesion size. Of note, CT densitometry was not performed in patients 4, 9, and 12, who had lesions smaller than 1 cm, two nodules, or borderline renal function.

Review of the images allowed the route for placement of the RF ablation probe to be planned. Once the patient was positioned to facilitate access of the target lesion, dispersive grounding pads were placed on the patients’ upper thighs. Patients were given aliquots of fentanyl citrate (Sublimaze; Akorn, Buffalo Grove, Ill) (50 µg intravenously) and midazolam hydrochlorate (Roche Laboratories, Nutley, NJ) (1 mg intravenously) as needed to maintain conscious sedation. Noninvasive monitoring of temperature, blood pressure, pulse, and O2 saturation was performed throughout the procedure. Continuous electrocardiographic monitoring was also performed in all patients. After the skin was prepared and draped in sterile fashion, local anesthesia was achieved with intradermal and subcutaneous 1% lidocaine (Xylocaine; AstraZeneca International, Wilmington, Del). With spiral CT guidance, a localizer 22-gauge Chiba needle was placed into the lesion. After confirmation of needle tip location, the RF ablation probe was placed into the center of the nodule by using tandem needle technique (32).

Eleven of 12 patients (17 nodules) were treated with a 6.4-F multiarray RF interstitial tissue ablation (RITA) probe (Starburst XL probe and model 1500 Electrosurgical Generator; RITA Medical Systems, Mountain View, Calif). The decision to treat patient 10 (two nodules) with a 19-gauge electrode and generator (Cool Tip; Radionics, Burlington, Mass) rather than the RITA probe was made because we believed that the proximity of this patient’s lesions to major airways and vessels (aorta, pulmonary veins, left lower lobe bronchus) would make adequate RITA tine deployment difficult. It should be noted, however, that the exclusion criterion for lesion proximity to major airways and vessels (<1 cm) was not met in any patient. Once appropriately positioned in the tumor, the RITA probe was deployed to place the tips of the tines at the periphery of the lesion. The deployment area covered by the RITA tines varied from 3 to 5 cm; for lesions larger than 5 cm, multiple overlapping RF ablations were performed. When the Cool Tip single-needle electrode was used, its tip was placed in the far center of the lesion. Care was taken to avoid placement of the tines into pulmonary vessels or other adjacent critical structures. If probe repositioning was required, the probe was not removed in its entirety; therefore, additional punctures were never required. Once the target temperature (90°C–95°C) was reached, a timer was set to monitor procedural duration. Tip cooling was not used during Cool Tip ablation because of the proximity of the patient’s tumor to major airways and vascular structures. RF ablation was terminated when the following had occurred: (a) 1-cm tumor margins were achieved, (b) ground-glass opacification was seen in the surrounding lung parenchyma at intraprocedural CT, and (c) sufficient time had elapsed, according to the probe manufacturer recommendations. As the probe was removed, the pulmonary parenchymal tract was also ablated. With regard to the RITA system, this involved complete withdrawal of the tines and use of the distal 1-cm tip for tract ablation. Figure 1 illustrates the set-up and process of RF ablation.



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  		Figure 1a. Spiral CT-guided percutaneous RF ablation of left lower lobe nodule with patient in prone position. Transverse thin-section CT was used to guide placement of (a) a 22-gauge localizer needle and (b) a multiarray probe. (c) After probe deployment, perinodular ground-glass opacification and associated trace pneumothorax are seen.

 


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  		Figure 1b. Spiral CT-guided percutaneous RF ablation of left lower lobe nodule with patient in prone position. Transverse thin-section CT was used to guide placement of (a) a 22-gauge localizer needle and (b) a multiarray probe. (c) After probe deployment, perinodular ground-glass opacification and associated trace pneumothorax are seen.

 


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  		Figure 1c. Spiral CT-guided percutaneous RF ablation of left lower lobe nodule with patient in prone position. Transverse thin-section CT was used to guide placement of (a) a 22-gauge localizer needle and (b) a multiarray probe. (c) After probe deployment, perinodular ground-glass opacification and associated trace pneumothorax are seen.

 
Technical Feasibility, Safety, and Nodule Densitometry for Following Up Tumors
Before commencement of the study, it was decided that an acceptable technical feasibility and safety profile would include the following: (a) ease of probe placement similar to that of needle placement during transthoracic needle biopsy, (b) ability to perform RF ablation on an outpatient basis, (c) complication profile similar to that described in the literature, and (d) chest tube placement rate similar to that reported during transthoracic needle biopsy. Both technical feasibility and safety were evaluated by the radiologist who performed the ablations (R.D.S.).

After the needle and RF ablation probe were removed, a postprocedural limited CT scan was obtained. Patients were observed for vital signs and pain for 4–6 hours in our posttreatment unit before discharge. All patients filled out identical questionnaires regarding the severity of pain they experienced during and after the procedure (on a scale from 1 to 5, where 1 = asymptomatic and 5 = severe pain or discomfort). Patients were given acetaminophen (Tylenol; McNeil Pharmaceuticals, Fort Washington, Pa) (650 mg every 4–6 hours) for mild pain and hydrocodone bitartrate and acetaminophen (Vicodin; Abbott Laboratories, Abbott Park, Ill) (one to two tablets with 5-mg hydrocodone bitartrate and 500-mg acetaminophen every 4–6 hours) for moderate pain. No patients reported severe pain or discomfort. Postprocedural chest radiographs were obtained at 1 and 4 hours to assess for pneumothorax. All pneumothoraces that were large (>20%), expanding, or symptomatic were treated with chest tube drainage. If no complications were observed, patients were discharged with routine follow-up by the referring physician but were instructed to immediately report any shortness of breath, bloody sputum, pain, or other symptoms. Patients were also questioned about symptoms at their scheduled follow-up visits (1, 3, 6, and 12 months after RF ablation), at which time their CT scans were also reviewed for pneumothorax, pleural effusion, and other pulmonary complications.

Follow-up nodule CT densitometry scans were evaluated by the radiologist who performed the ablations (R.D.S.). Since in only a few studies has CT densitometry been used as a method of following up ablated tumors, we were uncertain about the degree of change to expect after RF ablation. Follow-up CT scans were therefore evaluated only for change in lesion enhancement.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Successful placement of the RF ablation probe was achieved in all nodules. We believed that technical ease of placement was similar to that of needle placement during single-needle biopsy. Owing to the wide disparity in lesion geometry, ablation times varied greatly (range, 7.2–70.0 minutes), with a mean ablation time of 31.2 minutes. Of note, total procedure time varied greatly depending on the difficulty of accessing the nodule and the time for tine deployment, which were not recorded. The maximum power used during all RITA ablations was 150 W. On average, the probe was deployed 2.2 times in each lesion (range, 1–6 times). Owing to their nonspherical shape, seven of the lesions required repositioning and redeployment to ensure complete treatment. The four patients with multiple lesions underwent treatment of only one lesion at each visit, with the exception of patient 4, who underwent treatment for her two smallest lesions at the same session. Postablation images demonstrated ground-glass opacification surrounding all treated nodules, which likely represented localized edema and hemorrhage (Fig 1).

As of this writing, mean patient follow-up was 4.5 months (range, 1–12 months), with four patients followed up for 1–2 months, four for 3 months, two for 6 months, and two for 12 months. Of the eight patients who were followed up for at least 3 months, two had an increase in lesion size (mean increase, 54%; range, 31%–77%), and six had no significant interval change (mean change, 22%; range, 0%–40%). Of those lesions that remained stable in size on the basis of the World Health Organization criteria, four decreased, one increased, and one showed no change. These findings are summarized in Table 2. Figure 2 illustrates an example of postablation tumor change over a 12-month period.


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  		TABLE 2. Change in Target Lesion Size 3 Months after RF Ablation

 


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  		Figure 2a. Transverse contrast-enhanced thin-section CT scans obtained with the patient in prone position show lingula segment nodule before and at follow-up after RF ablation. (a) Baseline CT scan obtained before RF ablation shows 2.2 x 2.8-cm nodule with enhancement of 35.9 HU. (b) Follow-up 1-month CT scan depicts marked interval increase in nodule size, with early formation of thick-walled cavity and adjacent anterolateral complicated hydropneumothorax. Lesion enhancement increase from baseline was 0.0 HU. (c) Follow-up 3-month CT scan depicts interval regression of cavitary lesion, with enhancement increase from baseline of 4.0 HU and resolution of adjacent hydropneumothorax. (d) Follow-up 6-month CT scan shows further interval regression of cavitary lesion with enhancement increase from baseline of 26.0 HU. (e) Follow-up 12-month CT scan shows interval regression of lesion with scarring and enhancement increase from baseline of 15.0 HU.

 


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  		Figure 2b. Transverse contrast-enhanced thin-section CT scans obtained with the patient in prone position show lingula segment nodule before and at follow-up after RF ablation. (a) Baseline CT scan obtained before RF ablation shows 2.2 x 2.8-cm nodule with enhancement of 35.9 HU. (b) Follow-up 1-month CT scan depicts marked interval increase in nodule size, with early formation of thick-walled cavity and adjacent anterolateral complicated hydropneumothorax. Lesion enhancement increase from baseline was 0.0 HU. (c) Follow-up 3-month CT scan depicts interval regression of cavitary lesion, with enhancement increase from baseline of 4.0 HU and resolution of adjacent hydropneumothorax. (d) Follow-up 6-month CT scan shows further interval regression of cavitary lesion with enhancement increase from baseline of 26.0 HU. (e) Follow-up 12-month CT scan shows interval regression of lesion with scarring and enhancement increase from baseline of 15.0 HU.

 


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  		Figure 2c. Transverse contrast-enhanced thin-section CT scans obtained with the patient in prone position show lingula segment nodule before and at follow-up after RF ablation. (a) Baseline CT scan obtained before RF ablation shows 2.2 x 2.8-cm nodule with enhancement of 35.9 HU. (b) Follow-up 1-month CT scan depicts marked interval increase in nodule size, with early formation of thick-walled cavity and adjacent anterolateral complicated hydropneumothorax. Lesion enhancement increase from baseline was 0.0 HU. (c) Follow-up 3-month CT scan depicts interval regression of cavitary lesion, with enhancement increase from baseline of 4.0 HU and resolution of adjacent hydropneumothorax. (d) Follow-up 6-month CT scan shows further interval regression of cavitary lesion with enhancement increase from baseline of 26.0 HU. (e) Follow-up 12-month CT scan shows interval regression of lesion with scarring and enhancement increase from baseline of 15.0 HU.

 


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  		Figure 2d. Transverse contrast-enhanced thin-section CT scans obtained with the patient in prone position show lingula segment nodule before and at follow-up after RF ablation. (a) Baseline CT scan obtained before RF ablation shows 2.2 x 2.8-cm nodule with enhancement of 35.9 HU. (b) Follow-up 1-month CT scan depicts marked interval increase in nodule size, with early formation of thick-walled cavity and adjacent anterolateral complicated hydropneumothorax. Lesion enhancement increase from baseline was 0.0 HU. (c) Follow-up 3-month CT scan depicts interval regression of cavitary lesion, with enhancement increase from baseline of 4.0 HU and resolution of adjacent hydropneumothorax. (d) Follow-up 6-month CT scan shows further interval regression of cavitary lesion with enhancement increase from baseline of 26.0 HU. (e) Follow-up 12-month CT scan shows interval regression of lesion with scarring and enhancement increase from baseline of 15.0 HU.

 


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  		Figure 2e. Transverse contrast-enhanced thin-section CT scans obtained with the patient in prone position show lingula segment nodule before and at follow-up after RF ablation. (a) Baseline CT scan obtained before RF ablation shows 2.2 x 2.8-cm nodule with enhancement of 35.9 HU. (b) Follow-up 1-month CT scan depicts marked interval increase in nodule size, with early formation of thick-walled cavity and adjacent anterolateral complicated hydropneumothorax. Lesion enhancement increase from baseline was 0.0 HU. (c) Follow-up 3-month CT scan depicts interval regression of cavitary lesion, with enhancement increase from baseline of 4.0 HU and resolution of adjacent hydropneumothorax. (d) Follow-up 6-month CT scan shows further interval regression of cavitary lesion with enhancement increase from baseline of 26.0 HU. (e) Follow-up 12-month CT scan shows interval regression of lesion with scarring and enhancement increase from baseline of 15.0 HU.

 
All lesions that underwent CT densitometry before RF ablation showed increased enhancement from precontrast baseline; mean nodule enhancement was 46.8 HU (minimum, 19 HU; maximum, 107 HU). After RF ablation, lesions were often found to be heterogeneous and cavitary at CT; therefore, subsequent attenuation measurements were obtained by placing the region of interest marker on the most solid reproducible area of the lesion. Peripheral enhancement was not observed in any lesions. Mean enhancement decreased to 9.6 HU (minimum, 0 HU; maximum, 32 HU) 1–2 months after treatment (Fig 3). At this time, patient 3 was found to have increased contrast enhancement compared with baseline. This patient was suspected of having recurrent tumor on the basis of subsequent development of malignant pleural effusion. Three months after treatment, mean nodule enhancement was 14.4 HU (minimum, 4 HU; maximum, 28 HU). Patients 5 and 7 underwent 6-month follow-up CT densitometry. Patient 5 had postcontrast nodule enhancement of 26.0 HU (compared with 35.9 HU before RF ablation) and stable lesion size, whereas patient 7 had postcontrast nodule enhancement of 40.0 HU (compared with 33.6 HU before RF ablation) and a substantial increase in lesion size. Figure 4 illustrates postablation changes observed in these patients for lesion size and enhancement. Only patient 5 underwent 12-month follow-up CT densitometry. The 12-month follow-up CT scans showed postcontrast nodule enhancement of 15.0 HU or 41.8% increase (15.0/35.9 HU) from preablation baseline and stable lesion size (Fig 2). Figure 5 illustrates changes observed in lesion enhancement after RF ablation for all patients who underwent CT densitometry evaluation. A summary of lesion size and enhancement values measured in all patients over the 12 months after RF ablation is given in Table 3.



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  		Figure 3a. Transverse thin-section CT densitometry scans obtained with the patient in prone position. (a) Preablation precontrast CT scan shows lesion attenuation of 15 HU. (b) Preablation postcontrast CT scan shows maximum lesion attenuation of 88 HU (73-HU enhancement increase from baseline). (c) Precontrast 1-month follow-up CT scan shows lesion attenuation of 27 HU. (d) Postcontrast 1-month follow-up CT scan shows maximum lesion attenuation of 29 HU (2-HU enhancement from baseline).

 


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  		Figure 3b. Transverse thin-section CT densitometry scans obtained with the patient in prone position. (a) Preablation precontrast CT scan shows lesion attenuation of 15 HU. (b) Preablation postcontrast CT scan shows maximum lesion attenuation of 88 HU (73-HU enhancement increase from baseline). (c) Precontrast 1-month follow-up CT scan shows lesion attenuation of 27 HU. (d) Postcontrast 1-month follow-up CT scan shows maximum lesion attenuation of 29 HU (2-HU enhancement from baseline).

 


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  		Figure 3c. Transverse thin-section CT densitometry scans obtained with the patient in prone position. (a) Preablation precontrast CT scan shows lesion attenuation of 15 HU. (b) Preablation postcontrast CT scan shows maximum lesion attenuation of 88 HU (73-HU enhancement increase from baseline). (c) Precontrast 1-month follow-up CT scan shows lesion attenuation of 27 HU. (d) Postcontrast 1-month follow-up CT scan shows maximum lesion attenuation of 29 HU (2-HU enhancement from baseline).

 


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  		Figure 3d. Transverse thin-section CT densitometry scans obtained with the patient in prone position. (a) Preablation precontrast CT scan shows lesion attenuation of 15 HU. (b) Preablation postcontrast CT scan shows maximum lesion attenuation of 88 HU (73-HU enhancement increase from baseline). (c) Precontrast 1-month follow-up CT scan shows lesion attenuation of 27 HU. (d) Postcontrast 1-month follow-up CT scan shows maximum lesion attenuation of 29 HU (2-HU enhancement from baseline).

 


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  		Figure 4. Graph shows lesion size (product of largest diameters) (in square centimeters) and contrast enhancement (maximum postcontrast enhancement increase from baseline) for patients 5 and 7 at follow-up CT. {square} = patient 7 enhancement, {blacksquare} = patient 7 size, {triangleup} = patient 5 enhancement, {blacktriangleup} = patient 5 size.

 


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  		Figure 5. Graph shows contrast enhancement (maximum postcontrast enhancement increase from baseline) before RF ablation (0 months) and 1, 3, 6, and 12 months after RF ablation for the six patients who underwent follow-up CT densitometry.

 

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  		TABLE 3. Size and Enhancement of Lesions at Baseline, 1-2, 3, 6, and 12 Months after RF Ablation

 
None of the patients developed intraprocedural fevers or bleeding, and no overnight admissions were required. Twelve cases of intraprocedural pneumothorax were observed. Of these, two were believed to be small hemopneumothoraces and one a small hydropneumothorax (fluid collections that were freely mobile without loculation or other signs of complication were labeled hydrothoraces, while others were labeled hemothoraces). Catheter drainage was required in only two cases, in which patients had large (>20%) or expanding pneumothoraces; all other patients were asymptomatic and required no further treatment. Postprocedural chest radiographs obtained at 1 and 4 hours revealed no evidence of recurrent pneumothorax. Details regarding percentage size changes and characteristics of the pneumothoraces are given in Table 4. No intraparenchymal hemorrhage or hematoma was observed in any case.


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  		TABLE 4. Complications Observed during and after RF Ablation

 
Patient 5 developed shortness of breath 1 day after treatment and was found to have a large left-sided pneumothorax. Catheter drainage resulted in complete resolution, and overnight admission was not required. Follow-up CT performed 1 month later revealed a moderate hydropneumothorax; however, he was completely asymptomatic, and the hydropneumothorax was resolved on subsequent CT scans 2 months later. Patient 4 was found to have a moderate right-sided pneumothorax on a follow-up CT scan obtained 2 weeks after ablation of the first lesion (lesion 4A). Because the patient was completely asymptomatic, however, no treatment was required. Five days after the next ablation (lesions 4B and 4C), she presented with left-sided pleuritic chest pain and was found to have a moderate left hemopneumothorax. This was successfully treated by placing a 6-F pigtail catheter into the anterior superior pleural space (to treat the pneumothorax) and by placing an 8-F J catheter (Boston Scientific; Natick, Mass) into the posterior inferior pleural space (to treat the pleural effusion). At this time, the prior right pneumothorax was noted to have completely resolved. Twelve hours later, her symptoms had completely resolved, and the catheter was removed. Follow-up CT scans 4 months later showed resolution of the hemopneumothorax with complete reexpansion of the left lung.

Two cases of small pleural effusion were seen immediately after treatment, both of which resolved with observation alone. An additional small pleural effusion was noted 1 month after treatment, which also resolved spontaneously. Two patients reported pain after the procedure. One of these patients reported continued pain of moderate intensity for 1 month; the other patient reported moderate to severe pain for 3 months (pain was scored by patients as outlined in Materials and Methods). Both patients experienced adequate pain relief with hydrocodone bitartrate and acetaminophen (as needed) and did not require pain medication beyond 1 and 3 months, respectively. Table 4 summarizes complications encountered after RF ablation.

Two patients died during the course of our study. Patient 3 developed symptoms of increasing respiratory distress and dyspnea 2 months after RF ablation. A CT scan of the chest was obtained and revealed a small left-sided pleural effusion and patchy ground-glass opacification with moderate bronchial wall thickening in the left lower lobe. In light of the patient’s limited pulmonary reserve, a decision was made to aspirate the effusion with ultrasonographic guidance. Three hundred milliliters of serosanguinous fluid was aspirated, resulting in symptomatic improvement; however, the patient died 3 days later. Autopsy request was denied. Cytoanalysis of the pleural fluid revealed malignant cells consistent with metastatic adenocarcinoma from a primary lung tumor. Of note, this was the only patient in our study whose nodule demonstrated increased contrast enhancement at CT densitometry 1–2 months after RF ablation. In patient 2, who had colorectal cancer, a second primary tumor independent of the pulmonary malignancy for which RF ablation was performed was diagnosed 6 months after RF ablation. His death 1 month later was attributed to complications of a large-bowel obstruction.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
REFERENCES
 
Our preliminary results suggest that RF ablation of lung malignancies is safe and technically feasible. The percutaneous procedure is minimally invasive and can be performed with conscious sedation on an outpatient basis. Complications were generally minor and similar to those reported in the literature (17,33). Although Vaughn et al (34) recently reported a case of massive pulmonary hemorrhage in a 70-year-old man undergoing RF ablation of a lung malignancy, the patient in the current case was being treated with clopidogrel (Plavix; Bristol-Myers Squibb, New York, NY) (75 mg/d), a potent platelet inhibitor. No parenchymal hemorrhage was observed during any of our 19 ablations. Though pneumothorax was often encountered, our chest tube rate was similar to that reported in the literature during transthoracic needle biopsy (35). All other complications were self-limited. In contrast to the results of Dupuy et al (33), none of our patients developed fever during or after the procedure. Although two patients died during the course of our study, it is unlikely that their deaths were related to our protocol. One patient died 6 months after RF ablation for treatment of complications of a bowel obstruction. The other patient died of unknown reasons 2 months after RF ablation (autopsy request was denied). However, the fact that malignant pleural effusion was diagnosed a few days before his death suggests that he may have succumbed to complications of his primary disease.

The technical aspects of RF ablation for lung lesions still need improvement. One problem we encountered was occasional difficulty with accurate probe deployment. For patients with irregularly shaped lesions, it was often necessary to reposition the probe during the procedure. The lack of real-time CT made this particularly cumbersome, as it was necessary to stop, scan, and reposition the probe and tines several times. Even in patients with regularly shaped lesions, the traditional CT scanning methods required that the radiologist stop, leave the room for scanning, and then resume positioning of the probe. The use of CT fluoroscopy would likely facilitate accurate probe deployment, though the dose of radiation received by both the patient and radiologist might be somewhat greater (36). Another problem encountered was that of treating lesions that were small (<1 cm) or were located in proximity to critical structures. The smallest probe currently available is the 19-gauge Cool Tip probe; if smaller probes were to be developed, these lesions could be treated with greater accuracy. Fortunately, much research is underway to improve probe design (1).

Follow-up to determine the results of ablation was challenging. Patients demonstrated variable change in lesion size after treatment, with some showing what was likely either scar tissue development or growth and others remaining stable. Because ablated tissue adjacent to a lesion can mimic interval tumor enlargement at CT (30), lesion size was not believed to be a reliable measure of ablation success. It was noted that perinodular ground-glass opacities developed during the procedure; indeed, we used this as a treatment endpoint. Goldberg et al (37) reported similar opacities after ablation in the rabbit lung that corresponded histologically to coagulative necrosis of tumor. These opacities persisted to some degree after treatment and may contribute to the apparent increase in lesion size. Although we anticipate that successfully treated lesions will ultimately shrink in size as a result of scar formation, the duration of time for this to occur has not been established.

The use of nodule CT densitometry for solitary pulmonary nodules has received considerable attention in the literature (31). Our preliminary results suggest that nodule CT densitometry may eventually become a reliable method for following up tumors after ablation. All but one lesion demonstrated a dramatic decrease in contrast enhancement after RF ablation. The marked diminution of mean contrast material uptake at the 1–2-month follow-up may in part be a result of local vessel damage caused by RF ablation. At the 3-month follow-up, there was an increase in mean contrast material uptake compared with that at the 1–2-month visit, though all uptake profiles remained lower than those seen before treatment. We postulate that the increase in contrast material uptake may be a result of recovering circulation rather than tumor growth; however, to conclusively distinguish between normal circulation and viable tumor, biopsy or long-term follow-up would be necessary. Of the two lesions followed up with CT densitometry for at least 6 months, the lesion that demonstrated increased enhancement (from a preablation baseline) had substantially increased in size since the time of ablation, while the other remained stable in size. Further, at 1-year follow-up, the lesion that was stable in size at 6 months was still stable in size and maintained a contrast material uptake profile of less than 50% of baseline enhancement. Although lesion size alone may not be a reliable indicator of treatment effectiveness, stable lesion size in the context of consistently subbaseline lesion enhancement may prove to be an indication of treatment success.

One obvious limitation in the ability of CT densitometry to accurately reflect ablation success is the issue of tumor heterogeneity. Since tumors are often heterogeneous, particularly after RF ablation, whole-lesion enhancement measurements may fail to accurately reflect activity. For instance, after RF ablation, areas of successfully treated tumor will not enhance, while areas that contain viable tumor will. Measurement of whole-tumor enhancement would combine these two types of areas and produce misleading results. We attempted to compensate for tumor heterogeneity by placing the region of interest marker on the most solid reproducible area of the lesion rather than by measuring whole-lesion enhancement. In addition, since complete necrosis of tumors is often limited by untreated portions of the rim, we were prepared to measure rim enhancement; however, no tumors in this study demonstrated peripheral enhancement. Despite our efforts to account for lesion heterogeneity, some of our CT densitometry measurements may reflect a combination of viable and necrotic tumor.

It should be emphasized that our study was one of prospective feasibility. We do not claim to have proved that RF ablation is effective in treating lung malignancies or that CT densitometry values predict treatment success; to do so would have required autopsy or surgical resection to demonstrate necrotic tissue or, alternatively, extended follow-up to demonstrate lack of clinical recurrence. Postablation biopsy would have provided a more short-term reference standard, but the possibility of sampling error would remain. Long-term studies are needed to determine ablation effectiveness.

Although our study has limited follow-up, the correlation we observed between contrast material uptake profile and lesion activity is encouraging. Berber et al (30) reported similar trends in ablated hepatic tumors; a measurable decrease in contrast material uptake was found in successfully treated lesions. Though our study was not set up to evaluate ablation effectiveness as in the study of Berber et al, the fact that lesion enhancement values were clearly altered after RF ablation suggests that densitometry may eventually be useful for following up treated tumors. The fact that RF ablation can be performed on an outpatient basis with relatively minor and easily managed sequelae is also encouraging. Patients with focal disease who are unable to tolerate surgery from a cardiopulmonary standpoint could more easily withstand the minimally invasive nature of RF ablation. Likewise, patients with multifocal disease who would otherwise undergo surgical metastatectomy may instead elect to undergo RF ablation because thoracoscopy and open thoracotomy have numerous risks.

An important question for future studies, in addition to whether RF ablation prolongs survival, is whether it improves patients’ quality of life. The issue of palliation was not addressed in our study because, although all of our patients had disease refractory to conventional therapy, none were symptomatic during the study. Future studies to investigate the use of RF ablation in patients with symptoms of their disease are needed to further elucidate whether the benefits of RF ablation outweigh its potential complications.

In conclusion, our preliminary results suggest that RF ablation may prove to be a safe and feasible management option for unresectable pulmonary malignancies and that CT densitometry may have potential for future use as a noninvasive method of following up ablated tumors. Though proof of ablation effectiveness and absolute correlation of CT densitometry values with tumor activity are beyond the scope of this study, future studies that follow up ablated lesions for several years after RF ablation may provide this needed information.


   FOOTNOTES
 
Abbreviations: RF = radiofrequency, RITA = RF interstitial tissue ablation

Author contributions: Guarantors of integrity of entire study, R.D.S., J.G.G.; study concepts and design, R.D.S., J.G.G., S.B.H.; literature research, A.B.W., R.E.S.; clinical studies, R.D.S., S.B.H., R.E.S.; data acquisition and analysis/interpretation, A.B.W., R.E.S.; statistical analysis, A.B.W., R.E.S.; manuscript preparation and definition of intellectual content, A.B.W., R.E.S.; manuscript editing, revision/review, and final version approval, all authors


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 

  1. Goldberg SN, Dupuy DE. Image-guided radiofrequency tumor ablation: challenges and opportunities–part I. J Vasc Interv Radiol 2001; 12:1021-1032.[Medline]
  2. Mangru NN, Young ML, Wolff GS. Radiofrequency catheter ablation of a verapamil sensitive ventricular tachycardia. Pediatr Cardiol 1997; 18:235-236.[CrossRef][Medline]
  3. Prystowsky EN. Atrioventricular node re-entry: physiology and radiofrequency ablation. Pacing Clin Electrophysiol 1997; 20:552-571.[CrossRef][Medline]
  4. Simons GR, Klein GJ, Natale A. Ventricular tachycardia: pathophysiology and radiofrequency catheter ablation. Pacing Clin Electrophysiol 1997; 20:534-551.[CrossRef][Medline]
  5. Sweet WH, Mark VH, Hamlin H. Radiofrequency treatment of lesions in the ventral nervous system of man and cat: including case reports of eight bulbar pain-tract interruptions. J Neurosurg 1960; 17:213-215.[Medline]
  6. Tew JM, Keller JT. The treatment of trigeminal neuralgia by percutaneous radiofrequency technique In: Keener EB, ed. Clinical neurosurgery. Philadelphia, Pa: Williams & Wilkins, 1997.
  7. Laitinen LV, Bergenheim AT, Hariz MI. Leskell’s posteroventral pallidotomy in the treatment of Parkinson’s disease. J Neurosurg 1992; 76:53-61.[Medline]
  8. Patterson EJ, Scudamore CH, Owen DA, et al. Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion diameter. Ann Surg 1998; 227:559-565.[CrossRef][Medline]
  9. Goldberg SN, Gazelle GS, Dawson SL, et al. Tissue ablation with radiofrequency: effect of probe diameter, gauge, duration, and temperature on lesion volume. Acad Radiol 1995; 2:399-404.[CrossRef][Medline]
  10. Trubenbach J, Huppert PE, Pereira PL, et al. Radiofrequency ablation of the liver in vitro: increasing the efficacy by perfusion probes. Rofo Fortschr Geb Rontgenstr Bildgeb Verfahr 1997; 167:633-637. [German].
  11. Anzia Y, Lufkin R, DeSalles A, et al. Preliminary experience with MR guided thermal ablation of brain tumors. AJNR Am J Neuroradiol 1995; 16:39-48.[Abstract]
  12. Solbiati L, Livraghi T, Goldberg SN, et al. Percutaneous radio-frequency ablation of hepatic metastases from colorectal cancer: long-term results in 117 patients. Radiology 2001; 221:159-166.[Abstract/Free Full Text]
  13. Livraghi T, Goldberg SN, Solbiati L, et al. Percutaneous radio-frequency ablation of liver metastases from breast cancer: initial experience in 24 patients. Radiology 2001; 220:145-149.[Abstract/Free Full Text]
  14. Gazelle GS, Goldberg SN, Solbiati L, et al. Tumor ablation with radio-frequency energy. Radiology 2000; 217:633-646.[Abstract/Free Full Text]
  15. Mirza AN, Fornage BD, Sneige N, et al. Radiofrequency ablation of solid tumors. Cancer J 2001; 7:95-102.[Medline]
  16. Rossi S, Buscarini E, Garbagnati F, et al. Percutaneous treatment of small hepatic tumors by an expandable RF needle electrode. AJR Am J Roentgenol 1998; 170:1015-1022.[Abstract/Free Full Text]
  17. Dupuy DE, Goldberg SN. Image-guided radiofrequency tumor ablation: challenges and opportunities–part II. J Vasc Interv Radiol 2001; 12:1135-1148.[Medline]
  18. Primrose JN. Treatment of colorectal metastases: surgery, cryotherapy or radiofrequency ablation. Gut 2002; 50:1-5.[Free Full Text]
  19. Pollock RE. Manual of clinical oncology 7th ed. New York, NY: Wiley-Liss, 1999.
  20. Ihde DC, Minna JD. Non-small cell lung cancer. II. Treatment. Curr Probl Cancer 1991; 15:105-154.
  21. Licker M, Spiliopoulos A, Frey JG, et al. Risk factors for early mortality and major complications following pneumonectomy for non-small cell lung carcinoma of the lung. Chest 2002; 121:1890-1897.[Abstract/Free Full Text]
  22. Markos J, Mullan BP, Hillman DR. Preoperative assessment as a predictor of mortality and morbidity after lung resection. Am Rev Respir Dis 1989; 139:902-910.[Medline]
  23. Kearney DJ, Thomas HL, Reilly JJ. Assessment of operative risk in patients undergoing lung resection. Chest 1994; 105:753-759.[Abstract/Free Full Text]
  24. Belal A, Salah E, Hajjar W, et al. Pulmonary metastatectomy for soft tissue sarcomas: is it valuable? J Cardiovasc Surg (Torino) 2001; 42:835-840.[Medline]
  25. Pastorino U, Buysem M, Godehard F, et al. Long-term results of lung metastatectomy: prognostic analyses based on 5206 cases. J Thorac Cardiovasc Surg 1997; 113:37-49.[Abstract/Free Full Text]
  26. Kandolver D, Krower E, Tuchler H, et al. Long-term results after repeated surgical removal of pulmonary metastases. Ann Thorac Surg 1998; 65:909-912.[Abstract/Free Full Text]
  27. Rusch V. Pulmonary metastasectomy: current indications. Chest 1995; 107(6 suppl):322S-331S.[Medline]
  28. Weiser MR, Downey RJ, Leving DH, et al. Repeat resection of pulmonary metastases in patients with soft tissue sarcoma. J Am Coll Surg 2000; 191:184-191.[CrossRef][Medline]
  29. Handy JR, Asaph JW, Skokan L, et al. What happens to patients undergoing lung cancer surgery? outcomes and quality of life before and after surgery. Chest 2002; 122:21-28.[Abstract/Free Full Text]
  30. Berber E, Foroutani A, Garland AM, et al. Use of CT Hounsfield unit density to identify ablated tumor after laparoscopic radiofrequency ablation of hepatic tumors. Surg Endosc 2000; 14:799-804.[CrossRef][Medline]
  31. Swensen SJ, Viggiano RW, Midthun DE, et al. Lung nodule enhancement at CT: a multicenter study. Radiology 2000; 214:73-80.[Abstract/Free Full Text]
  32. Hightower DR, Laing FC, Jeffrey RB. A tandem guide for renal biopsy. J Ultrasound Med 1985; 4:441-443.[Abstract]
  33. Dupuy DE, Zagoria RJ, Akerley W, et al. Percutaneous radiofrequency ablation of malignancies in the lung. AJR Am J Roentgenol 2000; 174:57-59.[Free Full Text]
  34. Vaughn C, Mychaskiw G, Sewell P. Massive hemorrhage during radiofrequency ablation of a pulmonary neoplasm. Anesth Analg 2002; 94:1149-1151.[Abstract/Free Full Text]
  35. Klein JS, Zarka MA. Transthoracic needle biopsy. Radiol Clin North Am 2000; 38:235-266.[CrossRef][Medline]
  36. White CS, Meyer CA, Templeton PA. CT fluoroscopy for thoracic interventional procedures. Radiol Clin North Am 2000; 38:303-322.[CrossRef][Medline]
  37. Goldberg SN, Gazelle GS, Compton CC, et al. Radio-frequency tissue ablation of VX2 tumor nodules in the rabbit lung. Acad Radiol 1996; 3:929-935.[CrossRef][Medline]



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