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Letters to the Editor |
Department of Bioimaging and Radiological Sciences, Catholic University–Gemelli Hospital, Largo Gemelli 8, 00168 Rome, Italy
e-mail: anna.larici{at}rm.unicatt.it
Regarding the detection of unsuspected pulmonary emboli at routine multidetector computed tomography (CT) of the chest, we read with interest the article by Dr Gladish and colleagues (1), in the July 2006 issue of Radiology, in which the authors reported a prevalence of approximately 4% in the high-risk population of oncology patients. The authors included a majority of outpatients (372 of 403), with a prevalence of unsuspected emboli of 3.8% compared with a prevalence of 6% in the inpatients (31 of 403). These results confirmed those of previous studies (2,3), in which a higher prevalence of unsuspected pulmonary embolism was reported in inpatients.
Our unpublished experience does not fully support these data. In a larger population of oncology patients (n = 787), we observed a lower overall prevalence of incidental pulmonary emboli (1.9%). The majority of our population was represented by inpatients (701 of 787), among whom the prevalence of unsuspected emboli was 2.1%. No cases of pulmonary emboli were found among the 86 outpatients.
We had expected a greater prevalence of incidental emboli because the majority of patients were hospitalized and all had been routinely examined with a 16-section CT scanner, using a section thickness of 2.5 mm (vs 3.75 mm used by Dr Gladish and colleagues).
Our explanation for these results is the criteria used to select the study population. We did not include oncology patients with clinical suspicion of pulmonary emboli or patients who, at the time of examination, complained of symptoms suggestive of pulmonary embolism (shortness of breath, fatigue, chest pain). We considered all inpatients and outpatients with neoplastic disease for whom it was possible to retrospectively review the clinical data from our database.
Our results are in agreement with those of the study by O'Connell et al (4), in the October 2006 issue of Journal of Clinical Oncology. Those authors prospectively considered an oncology patient population and demonstrated that 75% of patients with unsuspected pulmonary emboli at the time of chest CT did have symptoms and signs of embolism, the most common of which were fatigue and shortness of breath. These symptoms had been overlooked by the referring physicians.
Therefore, we can conclude that when clinical criteria are taken into consideration the expected prevalence of incidental pulmonary emboli is lower than that reported in the article by Dr Gladish and colleagues.
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Edith M. Marom, MD *,
Bradley S. Sabloff, MD *, and
Reginald F. Munden, DMD, MD *
* Department of Diagnostic Radiology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Box 371, Houston, TX 77030
e-mail: ggladish{at}di.mdacc.tmc.edu
Department of Radiology, Korea Cancer Center Hospital, Seoul, Korea
We thank Dr Larici and colleagues for their interest in our article (1). They suggest that, on the basis on their experience, the prevalence of incidental pulmonary emboli in the oncology patient population is lower than we reported. Without publication of their data, we cannot comment in detail on their methods, but they do indicate that they excluded patients who were retrospectively determined to have symptoms of pulmonary embolism.
For the purpose of our study, we considered all emboli that were not previously known or anticipated based on the CT requisition to be incidental, regardless of retrospectively identified symptoms. This reflects the clinical practice of radiology. Although O'Connell et al (2) showed that many patients with reported unanticipated emboli had symptoms of dyspnea or fatigue, these symptoms are not infrequent in the oncology patient population. All of the published trial results (1,3–5) that include a full review of previously reported CT findings showed that a significant number of pulmonary emboli were not reported and that these unreported emboli tended to be smaller. The frequency of symptoms in patients with smaller emboli is not clearly known. These false-negative CT reports emphasize the need for radiologists to carefully evaluate the pulmonary vasculature on all chest CT scans with intravenous contrast material.
More important than the presence of symptoms is the clinical importance of these emboli. Are small or asymptomatic emboli as predictive of future embolic events or mortality as larger or symptomatic emboli? Should all patients with detected pulmonary emboli be treated? What form of therapy is most appropriate? Current clinical practice is that nearly all patients with detected pulmonary emboli are treated. In our institution, this typically means therapeutic anticoagulation for at least 6 months. Our results indicate the frequent presence of coexisting or subsequent thromboembolic disease, which supports this practice. However, a true long-term mortality benefit has not yet been shown in asymptomatic patients with incidentally detected pulmonary emboli.
We look forward to the publication of the results of Dr Larici and colleagues and those of future studies on the clinical importance of incidentally detected emboli.
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