Published online before print October 26, 2005, 10.1148/radiol.2373041380
(Radiology 2005;237:961-966.)
© RSNA, 2005
T Staging of Gastric Cancer: Role of Multi–Detector Row CT1
Seishi Kumano, MD, PhD2,
Takamichi Murakami, MD, PhD,
Tonsok Kim, MD,
Masatoshi Hori, MD, PhD,
Riccardo Iannaccone, MD,
Saki Nakata, MD,
Hiromitsu Onishi, MD,
Keigo Osuga, MD,
Kaname Tomoda, MD, PhD,
Carlo Catalano, MD and
Hironobu Nakamura, MD, PhD
1 From the Department of Radiology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 5650871, Japan (S.K., T.M., T.K., M.H., S.N., H.O., K.O., K.T., H.N.); and Department of Radiological Sciences, University of Rome La Sapienza, Rome, Italy (R.I., C.C.). Received August 9, 2004; revision requested October 19; revision received December 24; accepted January 24, 2005.
Address correspondence to T.M. (e-mail: murakami{at}radiol.med.osaka-u.ac.jp).
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ABSTRACT
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PURPOSE: To evaluate retrospectively the accuracy of multi–detector row computed tomography (CT) in the assessment of serosal invasion in patients with gastric cancer.
MATERIALS AND METHODS: The Ethics Committee does not require approval or informed consent for retrospective studies. Forty-one consecutive patients (24 men, 17 women; mean age, 68 years) with gastric cancer were included in this study. All patients were given 600 mL of tap water to drink and were positioned prone or supine on the scanning table. The detector row configuration included four detector rows, a section thickness of 1.25 mm, a pitch of 6, and a reconstruction interval of 0.63 mm. Transverse and multiplanar reconstruction images were simultaneously evaluated by two independent observers to assess the depth of tumor invasion in the gastric wall (ie, T stage). T staging at multi–detector row CT was compared with T staging at histologic evaluation (reference standard), which was performed by means of surgical or histologic examination of the resected specimen. We also calculated the sensitivity, specificity, and accuracy of multi–detector row CT for each observer in the assessment of serosal invasion.
RESULTS: Analysis of interobserver agreement showed substantial or almost perfect agreement (nonweighted 
value of 0.78 and weighted value of 0.85). Correct assessment of gastric wall invasion was 80% and 85% for observers 1 and 2, respectively. The sensitivity, specificity, and accuracy of multi–detector row CT in the assessment of serosal invasion were 90%, 95%, and 93%, respectively, for observer 1 and 80%, 97%, and 93%, respectively, for observer 2. Overstaging occurred in six patients, and understaging occurred in five patients. All understaged tumors were scirrhous subtype gastric cancer.
CONCLUSION: Multi–detector row CT scanning of patients with gastric cancer gave 93% accuracy in the assessment of serosal invasion in patients with gastric cancer.
© RSNA, 2005
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INTRODUCTION
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Gastric cancer is one of the major causes of death from malignant disease worldwide (1). In Japan, the incidence is highest, and gastric cancer is the leading cause of death from all malignant diseases (2). Accurate evaluation of the local extent of gastric cancer (the so-called T stage) is of pivotal importance in the choice of optimal therapeutic strategy. In particular, depiction of serosal invasion is important because serosal involvement has been demonstrated to be a poor prognostic factor (3,4). Indeed, when locally advanced gastric cancer with serosal invasion is present, a trial treatment of preoperative neoadjuvant chemotherapy is undertaken for downstaging to increase the chance for curative resection (5,6).
Double-contrast barium enema examination and endoscopy of the stomach are useful in demonstrating early gastric cancer (7). Both, however, have limitations in the preoperative T staging of gastric cancer. Endoscopic ultrasonography (US) has been reported to be the most effective diagnostic modality for the T staging of gastric cancer (8). Because endoscopic US can depict the normal gastric wall with five layers of internal structures, the depth of tumor penetration can be evaluated with excellent detail. Endoscopic US, however, has limitations in the depth of field of view that can be achieved and is operator dependent. Some authors have supported the use of laparoscopy as a more accurate tool for the preoperative staging of gastric cancer (9,10). Laparoscopy, however, cannot be routinely performed owing to its invasive nature.
Conventional and single–detector row helical computed tomography (CT) with water filling of the stomach have been reported to provide better detail for T staging (11–17). The development of multi–detector row CT scanners has introduced the possibility of protocols with a thinner section collimation, which translates into increased quality on transverse CT scans and multiplanar reconstructions. To our knowledge, no study has evaluated the effect of multi–detector row CT in demonstrating the depth of mural invasion in patients with gastric cancer. Thus, the purpose of our study was to evaluate retrospectively the accuracy of multi–detector row CT in the assessment of serosal invasion in patients with gastric cancer.
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MATERIALS AND METHODS
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Patients
Between July 2000 and June 2002, 41 consecutive patients who had gastric cancer that was diagnosed histologically during endoscopic biopsy and who underwent multi–detector row CT before surgery for international TNM classification (18) of the tumor were included in this study. There were 24 men and 17 women who ranged in age from 35 to 81 years (mean age, 68 years). All patients underwent either total or partial gastrectomy depending on the clinical stage of gastric cancer and on findings at surgery. Our Ethics Committee does not require approval or informed consent for retrospective studies.
In all patients, the resected stomach was submitted for histologic evaluation, and the area of the gastric cancer, as well as the surrounding normal-appearing gastric wall, was microscopically examined to determine the depth of tumor penetration. Histologic T staging was based on the international TNM classification (18). A stage of pT1 indicated tumor invasion into the lamina propria or submucosal layer; a stage of pT2, tumor invasion into the muscularis propria or subserosa; a stage of pT3, tumor penetration into the serosa without invasion of adjacent structures; and a stage of pT4, tumor invasion into adjacent structures. Histologically, tumors were classified as pT1 in 17 patients, as pT2 in 14 patients, as pT3 in eight patients, and as pT4 in two patients.
CT Protocol
CT examinations were performed by using a commercially available multi–detector row CT scanner (LightSpeed QXi; GE Medical Systems, Milwaukee, Wis). All patients were given 600 mL of tap water to drink to distend the stomach wall, and 5 minutes before the examination, 20 mg of scopolamine-N-butyl bromide (Buscopan; Boehringer Ingelhein Japan, Tokyo, Japan) was injected intramuscularly to induce gastric wall hypotonia and maintain hypotonia during the entire examination. The patient was positioned prone on the scanning table to avoid artifacts caused by air in the stomach (12). If the lesion was in the gastric cardia or fundus, as determined at barium enema examination and endoscopy, the patient was placed in the supine position for CT scanning. Precontrast scanning was not performed. A total of 100 mL of nonionic contrast material (iopromide, Proscope; Tanabe Seiyaku, Osaka, Japan) containing 300 mg of iodine per milliliter was injected intravenously at a rate of 3 mL/sec by using a power injector (Autoenhance A-50; Nemotokyoorindou, Tokyo, Japan). Scanning was started 70 seconds after intravenous injection of contrast material. Scanning began at the level of the dome of the right hemidiaphragm and ended at the lower edge of the stomach so as to include the entire liver. CT scanning parameters were as follows: four detector rows used; section thickness, 1.25 mm; pitch, 6; reconstruction interval, 0.63 mm; 200 mA; 120 kV; and tube rotation time, 0.8 second.
Transverse images, which had a section thickness of 2.5 mm and were obtained at 2.5-mm intervals, were created by using volumetric data obtained at multi–detector row CT and were printed as hard copies. To make interpretation easier, all images were printed as if the patient were in the supine position. Multiplanar reconstruction images were reconstructed on a workstation (Advantage Windows; GE Medical Systems). After the tumor location was confirmed, oblique coronal and oblique multiplanar reconstruction images that were obtained perpendicular to the stomach wall and included the tumor were reconstructed in all patients by a study coordinator. These multiplanar reconstruction images, which had a section thickness of 2.5 mm and were obtained at 2.5-mm intervals, were subsequently printed as hard copies.
Staging of Gastric Cancer with Multi–Detector Row CT
The mural invasion of gastric cancer into the gastric wall, as visualized at CT, was classified according to the TNM classification (12). A stage of T1 indicated that (a) strong enhancement with focal thickening was present in the inner and/or middle layer, but the outer layer showed no enhancement, (b) enhancement was present in the stomach wall, but the stomach wall was not thickened, or (c) no abnormal enhancement was seen in the entire stomach wall, and there was no evidence of transmural tumoral involvement. A stage of T2 indicated that the entire stomach wall was abnormally enhanced and that, though this abnormal enhancement was accompanied by wall thickening, the surface of the outer layer in contact with the fatty layer surrounding the stomach was smooth. A stage of T3 indicated that the entire stomach wall was abnormally enhanced, that this abnormal enhancement was accompanied by wall thickening, and that linear or reticular structures were observed in the fatty layer surrounding the stomach. A stage of T4 indicated that the changes described for T3 staging extended into adjacent contiguous organs.
Histologic Types of Gastric Cancer
Clinically and histologically, gastric cancers are typically classified as either differentiated or undifferentiated (19,20). According to the Japanese classification of gastric cancer (21), gastric cancers are histologically classified into five types: papillary adenocarcinoma, tubular adenocarcinoma (including well-differentiated and moderately differentiated types), poorly differentiated adenocarcinoma (including solid or nonsolid types), signet-ring cell carcinoma, and mucinous adenocarcinoma. Thus, the differentiated gastric cancers included papillary and tubular adenocarcinomas, whereas the undifferentiated gastric cancers included poorly differentiated adenocarcinoma, signet-ring cell carcinoma, and mucinous adenocarcinoma (21,22).
In gastric cancer, the relationship between the cancer and the stroma can be classified according to three subtypes: medullary, intermediate, and scirrhous (21). For the medullary subtype, the stroma is scanty; for the scirrhous subtype, the stroma is abundant; and for the intermediate subtype, the stroma is between that of the medullary subtype and scirrhous subtype. In our series, we evaluated both the histologic type and subtype to determine the correlation between T staging with multi–detector row CT and T staging with histologic evaluation.
Image Interpretation
Transverse and multiplanar reconstruction images were simultaneously evaluated by two experienced radiologists (T.K. and S.N., with 16 and 11 years of experience in abdominal CT, respectively) who interpreted the images independent of each other. The radiologists were unaware of the results of the upper gastrointestinal series, endoscopic examination, and surgical or histologic analysis of the resected specimen.
In this series, the histologic type and subtype of gastric cancer were compared with T staging at multi–detector row CT, as determined by the two radiologists (observers). For each histologic type or subtype, the number of tumors that were staged was calculated for each observer. T staging at multi–detector row CT was compared with T staging at histologic evaluation. The percentage of cases in which staging at CT was concordant with the histologic classification was reported separately for each observer. We also calculated the sensitivity, specificity, and accuracy of multi–detector row CT in the assessment of serosal invasion by each observer.
Statistical Analysis
To evaluate the diagnostic reproducibility of the technique, interobserver agreement was analyzed by using both nonweighted and weighted binary statistics (Excel 2002; Microsoft, Redmond, Wash) (23). A value of 0.01–0.20 indicated slight agreement; 0.21–0.40, fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, substantial agreement; and 0.81–1.0, almost perfect agreement.
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RESULTS
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There was one papillary adenocarcinoma, two well-differentiated tubular adenocarcinomas, 13 moderately differentiated tubular adenocarcinomas, two solid poorly differentiated adenocarcinomas, 15 nonsolid poorly differentiated adenocarcinomas, seven signet-ring cell carcinomas, and one mucinous adenocarcinoma (Table 1). Regarding the histologic subtype of gastric cancer, there were four medullary subtype gastric cancers, 21 intermediate subtype gastric cancers, and 16 schirrus subtype gastric cancers (Table 2).
Regarding T factor, analysis of interobserver agreement showed a nonweighted value of 0.78, which indicated substantial agreement between the observers, and a weighted value of 0.85, which indicated almost perfect agreement between the observers. These results demonstrate good diagnostic reproducibility of the technique.
A correct assessment of the depth of mural invasion in the gastric wall (T stage) was obtained in 33 (80%) of 41 patients for observer 1 and in 35 (85%) of 41 patients for observer 2 (Table 3). The sensitivity, specificity, and accuracy of the technique in determining the degree of serosal invasion were 90%, 95%, and 93%, respectively, for observer 1 and 80%, 97%, and 93%, respectively, for observer 2 (Table 4). False-negative findings occurred in one tumor for observer 1 and in two tumors for observer 2. False-positive findings occurred in two tumors for observer 1 and in one tumor for observer 2.
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TABLE 3. Comparison of T Staging with Multi–Detector Row CT versus T Staging with Histologic Evaluation For Each Observer
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TABLE 4. Sensitivity, Specificity, and Accuracy of Multi–Detector Row CT in Demonstrating Serosal Invasion, as Determined for Each Observer
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T1 Tumors
For observer 1, 13 tumors were correctly classified as T1, and for observer 2, 15 tumors were correctly classified as T1 (Table 3, Fig 1 ). Of the 17 tumors that were staged as pT1 at histologic evaluation, two were overstaged as either T2 or T3 by both observers at multi–detector row CT. One of these tumors was a large protruding mass with marked contrast enhancement at CT (Fig 2). Both observers interpreted the large enhanced mass as a T2 or T3 tumor because the mass seemed to be accompanied by thickening of the entire gastric wall or by irregularities in the serosal surface. Histologic examination of the tumor revealed massive invasion into the submucosal layer; this tumor was determined to be a nonsolid poorly differentiated adenocarcinoma and intermediate subtype (Tables 1, 2). In the other tumor, histologic examination revealed that the cancer was limited to within the mucosa. This tumor was a moderately differentiated tubular adenocarcinoma and intermediate subtype (Tables 1, 2). Retrospectively, both observers might have confused a giant fold in the greater curvature of the stomach with an enhanced tumor mass. Two tumors were overstaged as T2 by observer 1 only. These tumors were seen as well-enhanced masses at CT that spread widely into the submucosal layer at histologic examination. Histologically, these tumors were moderately differentiated tubular adenocarcinomas (Tables 1, 2).
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Figure 1a. Images obtained in 80-year-old woman with stage T1 gastric tumor. (a) Transverse CT scan shows enhancement with focal thickening (arrow) in inner and middle layers but does not demonstrate thickening and enhancement of entire stomach wall. (b) Histologic micrograph shows tumor involvement in mucosal and submucosal layers (arrow) but not in muscularis propria (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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Figure 1b. Images obtained in 80-year-old woman with stage T1 gastric tumor. (a) Transverse CT scan shows enhancement with focal thickening (arrow) in inner and middle layers but does not demonstrate thickening and enhancement of entire stomach wall. (b) Histologic micrograph shows tumor involvement in mucosal and submucosal layers (arrow) but not in muscularis propria (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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Figure 2a. Images obtained in 50-year-old man with stage T1 gastric tumor that was overstaged as T2 or T3. (a) Transverse CT scan shows large enhanced tumor (arrow) on lesser curvature of stomach. Tumor was overstaged as either T2 or T3 by observers because large tumors can be confused with wall thickening and irregularities in serosal portion of enhanced tumor (black arrow). (b) Histologic micrograph shows massive submucosal invasion (arrow) but no subserosal invasion. (Hematoxylin-eosin stain; low-power magnification.)
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Figure 2b. Images obtained in 50-year-old man with stage T1 gastric tumor that was overstaged as T2 or T3. (a) Transverse CT scan shows large enhanced tumor (arrow) on lesser curvature of stomach. Tumor was overstaged as either T2 or T3 by observers because large tumors can be confused with wall thickening and irregularities in serosal portion of enhanced tumor (black arrow). (b) Histologic micrograph shows massive submucosal invasion (arrow) but no subserosal invasion. (Hematoxylin-eosin stain; low-power magnification.)
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T2 Tumors
For both observers, 12 of 14 tumors were correctly staged as T2 (Table 3, Fig 3). Of the 14 tumors that were staged as pT2 at histologic evaluation, one was overstaged as T3 by both observers at multi–detector row CT. In this tumor, strandlike structures that extended from the outer gastric surface and into the surrounding fat plane were seen; this was considered suggestive of serosal involvement. At histologic examination, the margin of the tumor reached but did not involve the serous membrane. This tumor was a well-differentiated tubular adenocarcinoma and intermediate subtype (Tables 1, 2). One tumor was understaged by both observers. This tumor was a nonsolid poorly differentiated adenocarcinoma and scirrhous subtype (Tables 1, 2). At CT, this lesion was clearly seen, but the enhancement of the gastric wall was incomplete.
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Figure 3a. Images obtained in 72-year-old man with stage T2 gastric tumor. (a) Transverse CT scan shows abnormal enhancement in entire stomach wall accompanied by wall thickening (arrow). (b) Histologic micrograph shows tumor involvement in muscularis propria (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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Figure 3b. Images obtained in 72-year-old man with stage T2 gastric tumor. (a) Transverse CT scan shows abnormal enhancement in entire stomach wall accompanied by wall thickening (arrow). (b) Histologic micrograph shows tumor involvement in muscularis propria (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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T3 Tumors
Six of eight tumors were correctly staged as T3 by observers 1 and 2 (Table 3, Fig 4). One tumor was overstaged by observer 1. This tumor was a solid poorly differentiated adenocarcinoma and medullary subtype (Tables 1, 2) and was located on the posterior wall of the antrum of the stomach. This tumor was adjacent to the pancreas, and the border between the gastric tumor and the body of the pancreas was unclear. Observer 1 suspected that the tumor had invaded the pancreas body. One of the eight tumors was understaged by both observers (Fig 5). At CT, the surface of the outer layer of the stomach wall, including the lesion, was smooth. This tumor was a nonsolid poorly differentiated adenocarcinoma and scirrhous subtype (Tables 1, 2). Histologic findings revealed that this tumor had minimal infiltration of cancer cells into the perigastric adipose tissue without macroscopic mass formation. One of the eight tumors was understaged by observer 2. This tumor was a nonsolid poorly differentiated adenocarcinoma and scirrhous subtype.
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Figure 4a. Images obtained in 64-year-old man with stage T3 gastric tumor. (a) Transverse CT scan shows abnormal enhancement in entire stomach wall accompanied by wall thickening (arrow); linear or reticular structures are observed in fatty layer surrounding stomach. (b) Histologic micrograph shows extraserosal invasion (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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Figure 4b. Images obtained in 64-year-old man with stage T3 gastric tumor. (a) Transverse CT scan shows abnormal enhancement in entire stomach wall accompanied by wall thickening (arrow); linear or reticular structures are observed in fatty layer surrounding stomach. (b) Histologic micrograph shows extraserosal invasion (arrowhead). (Hematoxylin-eosin stain; low-power magnification.)
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Figure 5a. Images obtained in 63-year-old man with T3 gastric cancer that was understaged as T2. (a) Transverse CT scan shows gastric cancer on body of stomach. Tumor (arrow) was incorrectly staged as T2 by both observers because surface of outer layer appears smooth. (b) Histologic micrograph shows minimal infiltration of cancer cells (arrowhead) into perigastric adipose tissue. (Hematoxylin-eosin stain; low-power magnification.)
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Figure 5b. Images obtained in 63-year-old man with T3 gastric cancer that was understaged as T2. (a) Transverse CT scan shows gastric cancer on body of stomach. Tumor (arrow) was incorrectly staged as T2 by both observers because surface of outer layer appears smooth. (b) Histologic micrograph shows minimal infiltration of cancer cells (arrowhead) into perigastric adipose tissue. (Hematoxylin-eosin stain; low-power magnification.)
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T4 Tumors
Two tumors were correctly staged as T4 because of the absence of normal fat cleavage planes with surrounding organs at CT (Fig 6).
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Figure 6a. Images obtained in 66-year-old man with stage T4 gastric tumor. (a) Transverse CT scan shows extension (arrow) to adjacent transverse colon. (b) Histologic micrograph shows tumor (arrow) invasion in colon. (Hematoxylin-eosin stain; low-power magnification.)
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Figure 6b. Images obtained in 66-year-old man with stage T4 gastric tumor. (a) Transverse CT scan shows extension (arrow) to adjacent transverse colon. (b) Histologic micrograph shows tumor (arrow) invasion in colon. (Hematoxylin-eosin stain; low-power magnification.)
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DISCUSSION
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Early studies of CT in patients with gastric cancer have focused on the thickness of the normal gastric wall. A gastric wall that measures more than 1 cm thick when the stomach is moderately distended could be caused by any gastric abnormality, including benign and malignant conditions (24). There has been controversy with regard to the effectiveness of CT for T staging of gastric cancer, and an overall accuracy of 66%–82% has been reported in the literature (11–15,17). In these studies, however, researchers commonly used a section thickness of 5–10 mm. When such a section thickness is used, CT has the drawback of producing partial volume artifacts, especially in some transitional zones where the gastric wall is tangent to the scanning plane. Multi–detector row CT, however, can overcome this limitation because of its ability to provide fast imaging. The advent of multi–detector row CT scanners allows us to obtain images with a section thickness of 1.25 mm through large areas of the anatomy without concern for breathing artifacts or x-ray tube-cooling problems. Whereas multiplanar reconstruction images, as obtained with so-called single–detector row helical CT scanners, have the limitation of low longitudinal image resolution, multi–detector row CT scans provide reduced partial volume effects and can improve the quality of multiplanar reconstruction images. Therefore, we expected that we could assess the depth of mural invasion of gastric cancer with multi–detector row CT scanners. Our cumulative accuracy in determining the T stage is clearly superior to that obtained by using standard CT techniques (11–15). Moreover, in our series, interobserver variation was low between the two observers, which indicated a good diagnostic reproducibility of the technique.
Diagnosis of serosal invasion is also important because serosal invasion is a factor in poor prognosis. For patients with serosal invasion, a trial treatment of preoperative neoadjuvant chemotherapy is undertaken for downstaging to increase the chance for curative resection. The accuracy in determining serosal invasion was 93% for both observers. Results of previous studies indicated 80%–87% accuracy with conventional and single–detector row helical CT (11–15,17). Although it is difficult to simply compare our results with those obtained in previous studies, the accuracy in determining serosal invasion by using multi–detector row CT tends to be high and is almost the same as that obtained with endoscopic US, which is invasive and depends on investigator's technique (8). Although the present study focuses on T staging, CT—in addition to facilitating detection of mural invasion—provides a clear advantage when compared with other techniques because CT has the ability to enable assessment of the liver parenchyma and regional lymph nodes for the presence of metastases.
According to the Japanese classification of gastric carcinoma (21), the histologic subtype of gastric carcinoma is classified according to the relationship between the cancer and the stroma. Scirrhous subtype carcinomas have an abundant stroma. In our series, all understaged tumors were scirrhous subtype carcinomas. Scirrhous subtype carcinomas have few vessels in rich interstitial tissues. One of the reasons for understaging a T2 tumor as a T1 tumor may be related to the poor enhancement of gastric cancer. Concretely, complete enhancement of the entire stomach wall was not seen in cases where T2 tumors were understaged as T1. Adachi et al (25) reported that differentiated carcinoma either has a normal vascular structure or is hypervascular and that undifferentiated carcinoma is hypovascular. There is a tendency for the scirrhous subtype to often include undifferentiated carcinoma. Moreover, in some cases of scirrhous subtype carcinoma, T3 tumors were understaged as T2 because the outer surface of the stomach wall showed smooth and regular characteristics and because the infiltration of tumor cells in the perigastric adipose tissue was minimal. Rossi et al (17) speculated that, in intestinal gastric cancer, cells are more closely linked and are organized in solid or glandular structures that completely replace the gastric layers. Minimal infiltration of cancer cells into the perigastric adipose tissue without macroscopic mass formation seemed to be beyond the resolution of multi–detector row CT in this study. Multi–detector row CT scans obtained with a thinner section thickness, such as 1.25 or 0.63 mm, may depict the outer line (ie, the serosal side of the gastric wall) adjacent to epigastirc fat. High-grade malignant tumors that show poor prognosis, such as undifferentiated type or scirrhous subtype carcinomas, should be evaluated carefully.
Of the six tumors that were overstaged by either observer, four of them were T1 tumors that had been overstaged as T2 or T3 tumors. These tumors had well-enhanced protruding lesions that could be confused with well-enhanced stomach wall thickening or with irregularities in the serosal surface. On the other hand, these four tumors were differentiated tumors, and there were no scirrhous subtype carcinomas.
It is well known that gastric carcinoma can be divided into two major categories (19,26,27). These categories include the so-called intestinal, expanding, or differentiated type and the diffuse, infiltrative, or undifferentiated type. The relationship between the cancer and the stroma is closely correlated with histologic type for Japanese gastric cancer classification. These histologic characterizations may affect the sensitivity of multi–detector row CT for the staging of gastric carcinoma.
Our study has several limitations. First, there was a potential bias in image interpretation. Although blinded to the results of the upper gastrointestinal series, endoscopic examination, and surgical or histopathologic analysis of the resected specimen, the observers were aware of the presence of a tumor. Thus, in our study, there might be an overestimation of the ability of multi–detector row CT to depict gastric cancer. Because our aim was to investigate the ability of multi–detector row CT to facilitate evaluation of the depth of mural invasion but not to show the detectability of gastric cancer on multi–detector row CT, we believe that this cannot be construed as a major limitation of our study.
Another potential criticism of our study could be related to the use of scopolamine-N-butyl bromide to induce gastric wall hypotonia. Indeed, this drug is currently unavailable in the United States. Glucagon hydrochloride, however, can achieve similar results (17).
In conclusion, multi–detector row CT in patients with gastric cancer is a valid method for preoperative staging, especially given the high accuracy of CT for the assessment of serosal invasion in gastric cancer.
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ACKNOWLEDGMENTS
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We thank Eiji Sugihara, MD, PhD, and Hisashi Abe, MD, for their clinical and experimental efforts.
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FOOTNOTES
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2 Current address: Department of Radiology, Ehime University School of Medicine, Ehime, Japan 
Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, H.N.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, S.K., T.M., T.K., R.I., K.O.; clinical studies, S.K., T.K., M.H., S.N., H.O., K.T.; statistical analysis, T.M., M.H.; and manuscript editing, T.M., R.I., C.C., H.N.
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ABSTRACT
INTRODUCTION
