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Incomplete Colonoscopy in Patients with Occlusive Colorectal Cancer: Usefulness of CT Colonography According to Tumor Location

Incomplete Colonoscopy in Patients with Occlusive Colorectal Cancer: Usefulness of CT... Yonsei Med J 48(6):934-941, 2007 DOI 10.3349/ymj.2007.48.6.934 Incomplete Colonoscopy in Patients with Occlusive Colorectal Cancer: Usefulness of CT Colonography According to Tumor Location 1 2 2 3 3 1 Joo Hee Kim, Won Ho Kim, Tae Il Kim, Nam Kyu Kim, Kang Young Lee, Myeong-Jin Kim, and Ki Whang Kim 1 2 3 Department of Radiology, Division of Gastroenterology, Department of Internal Medicine, Department of Surgery, Yonsei University College of Medicine, Seoul, Korea. Purpose: We sought to evaluate the clinical usefulness of Key Words: CT colonography, colorectal neoplasms, staging, CT colonography (CTC) after incomplete conventional colonic obstruction colonoscopy (CC) for occlusive colorectal cancer (CRC) according to the tumor location. Materials And Methods: Seventy-five patients with occlusive CRC underwent subsequent CTC immediately after incomplete CC. Fifty-nine INTRODUCTION patients had distal CRC and 16 had proximal colon cancer. Experienced radiologists prospectively analyzed the location, Conventional colonoscopy (CC) is the current length, and TNM staging of the main tumor. The colorectal standard technique for evaluating the entire polyps in the remaining colorectum and additional ex- colon. Full colonic evaluation is especially traluminal findings were also recorded. Sixty-seven patients important in patients with colorectal malignancy underwent colorectal resection. We retrospectively analyzed because of the high prevalence of synchronous the surgical outcome and correlated CTC and CC findings. adenomas and carcinomas. At the same time, CC Results: The overall accuracies of tumor staging were: T staging, 86%; N staging (nodal positivity), 70% (80%); and fails to show the entire colon in about 6-26% of intra-abdominal M staging, 94%. Additional colonic polyps cases, mainly due to occlusive colorectal cancer 1-4 were found in 23 patients. Six synchronous carcinomas were (CRC). About 15% of patients with CRC detected (9%); three in the proximal colon and three in the present with large bowel obstruction. In this distal colon of occlusion. Clinically significant localization situation, double-contrast barium enema (DCBE) errors at CC were noted in 8 patients (12%, 5 proximal colon might be the next choice for complete evaluation cancers and 3 distal CRCs) and were corrected by CTC. After 5,6 of the proximal colon. This method may be CTC, the surgeons modified the initial surgical plan in 11 limited, however, by poor coating of the cases (16%). Conclusion: In occlusive CRC, CTC is not only useful in the evaluation of the proximal bowel, but can also distended proximal bowel, low accuracy in provide surgeons with accurate information about staging and detecting small polyps, and a problem of residual tumor localization. CTC is recommended when endoscopists barium during surgery. Currently, computed encounter occlusive CRC, regardless of tumor location. tomography colonography (CTC) is regarded as a promising technique for complete evaluation of the proximal colon and simultaneous assessment 7-9 of extraluminal status. Received May 21, 2007 Several reports discuss the usefulness of CTC Accepted July 6, 2007 This work was supported by Yonsei University Research Fund immediately after incomplete CC due to occlusive of 2004. CRC, and most focus on cases of distal colon or Reprint address: requests to Dr. Joo Hee Kim, Department of rectal carcinoma. These promising results have Diagnostic Radiology, Yonsei University College of Medicine, 612 promoted CTC as a choice for preoperative Eonjuro, Gangnam-gu, Seoul 135-720, Korea. Tel: 82-2-2019-3510, evaluation after incomplete CC due to distal Fax: 82-2-3462-5472, E-mail: [email protected] Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas occlusive CRC. However, to our knowledge, no mide), room air was carefully insufflated using a report has documented the usefulness of CTC manual balloon pump through a rectal enema according to tumor location, particularly for tube according to the patient's tolerance. Air proximal occlusive colon cancers. The aim of this filling and distension of the colon were evaluated study was to evaluate the clinical usefulness of on the CT scout before CTC. Once bowel distention CTC in cases of incomplete CC due to occlusive was adequate, CTC was performed after power CRC and to compare the results of CTC in injection of 120 mL (3mL/sec; scanning delay, 60 proximal versus distal occlusive CRCs. sec) of an iodinated IV contrast agent. Two sets of images, one obtained with the patient supine and the other with the patient prone, were MATERIALS AND METHODS generated. CT parameters included 4× 2-mm detector collimation, 120kV, 150-200 mAs, and a Patients pitch of 1.25. Axial CT images were reconstructed as 3-mm slices with a 1.5-mm reconstruction From Mar 2002 to Feb 2004, 75 patients with interval. CT images were transferred to a remote occlusive CRC underwent subsequent CTC PC-based workstation using commercially available immediately after incomplete CC. Experienced software (Rapidia; Infinitt). The processed images internists with gastrointestinal subspecialty training included multiplanar reformatted, ray-sum, and performed CC. Bowel cleansing was provided by virtual colonoscopy images. ingesting 4 L of a polyethylene glycol electrolyte solution in a standard manner before the Image analysis procedure. Initially, the patients were divided into The experienced gastrointestinal radiologist two groups according to the colonoscopic finding: proximal colon cancer (cancer from the cecum to prospectively analyzed tumor localization (tumor splenic flexure) and distal colon and rectal cancer location and the length of the involved segment), (descending-sigmoid colon cancer, rectosigmoid, and TNM staging of the main tumor, using TNM and rectal cancer, but not anal cancer). The classification in the 6th edition of the AJCC and occlusion site, cause of occlusion, and size and UICC system for rating cancer of the colon and the rectum from 2002 (Sobin and Wittekind, 2002). number of other colorectal polyps distal to the occlusion were recorded. Colorectal polyps in the remaining colorectum Seven patients with peritoneal dissemination of proximal and distal to the obstruction were the malignancy and one patient with extensive assessed. Additional extraluminal findings were hepatic metastasis were excluded. Ultimately, 67 also recorded. Postoperative CC was performed to patients (14 proximal and 53 distal occlusive CRC) control the CTC findings in the proximal part of the colon (n=35). with 73 histopathologically proven carcinomas were included in this study, consisting of 45 men Surgical resection was performed after multi- and 22 women (mean age of 58.2 years with a disciplinary team planning with surgeons, in- range of 19-86 years). Informed consent was ternists, and a radiologist. We retrospectively obtained from all patients and all examinations analyzed the surgical outcome and correlated were performed in accordance with the recom- CTC findings with the histopathologic findings and preoperative/postoperative CC results, in- mendations of our institutional review board. Follow-up CC was carried out in 37 patients with cluding the accuracy of CTC for TNM staging (n surgically treated occlusive CRC. =73), accuracies of CTC and CC in localization of the main tumor (n =67), and accuracies of CT protocol CTC and CC in polyp detection, distal (n=75) versus proximal (n=35) to the obstruction. In polyp detection by CTC, sensitivity, specificity, CTC was performed with a 4-channel multi- detector row CT scanner (GE medial; LightSpeed). positive predictive value (PPV), and negative After injection of buscopan (hyoscine n-buthylbro- predictive value (NPV) of CTC were calculated, Yonsei Med J Vol. 48, No. 6, 2007 Joo Hee Kim, et al. per person and per lesion. central nodal metastasis (n=3) (2 had multifocal lesions). A small, subcapsular hepatic metastasis was found that was missed on CT. Small metastatic RESULTS para-aortic nodes in another patient were also missed on CT preoperatively. In determination of Complete CTC examination was achieved in all peritoneal dissemination, one patient was over- 75 patients who underwent CTC immediately staged and one was under-staged. after incomplete CC due to occlusive colon cancer. In 14 patients (21%, 6 proximal colon cancers Sixteen patients had proximal colon cancer and 59 and 8 distal CRCs), the exact site of the cancer patients had distal CRC. Seventy-three adenocar- was initially misdiagnosed on CC. Localization cinomas were retrieved from 67 patients. On histopathological examination, 12 of 73 tumors (16%) were staged as pT1/2, 53 (73%) as pT3, and 8 (11%) as pT4; 28 of 73 (38%) were staged as pN0, 27 (37%) as pN1, and 18 (25%) as pN2; and 56 of 67 (84%) were staged as intra-abdominal pM0 and 11 (16%) as pM1. The overall accuracies of TNM staging on CTC were T staging, 86%; N staging, 70%; and intra- abdominal M staging, 94% (Table 1). The overall accuracy for prediction of pericolic fat infiltration was 96%. In advanced CRC ( pT3), overstaging and understaging occurred in three and four patients, respectively. These cases were all incor- rectly interpreted as to whether the tumor Fig. 1. A 39-year-old woman with mid transverse colon perforated the visceral peritoneum (T4) or not cancer. Axial CT scan reveals irregular wall thickening (T3). The overall accuracy for prediction of nodal with luminal narrowing of the transverse colon with pericolic fat infiltration (arrow). The visceral peritoneum positivity (involved or tumor-free) was 80%. was not identifiable and no solid organ invasion was Intra-abdominal metastatic lesions were found in visible, which suggested stage T3. However, the 11 patients: 4 liver metastasis (n=4), peritoneal pathologic stage of this lesion proved to be pT4 because dissemination of the malignancy (n=6), and of tumor invasion into the visceral peritoneum. Table 1. Pathologic and CTC Staging of TNM CTC staging Pathologic staging T1/T2 T3 T4 N0 N1 N2 M0 M1 T (n=73) T1/T2 12 9 3 T3 53 50 3 T4 8 4 4 N (n=73) N0 28 16 9 3 N1 27 2 20 5 N2 18 1 2 15 M (n=67) M0 56 55 1 M1 11 3 8 Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas errors were clinically insignificant in six of the occlusive cancer in 12 patients. The accuracy of patients, and the planned operations were carried CTC per patient in the distal group was 96%; out without modification. Clinically significant sensitivity, 83%; specificity, 98%; PPV, 92%; and localization errors were noted in eight patients NNV, 97%. Forty-two abnormalities (including 3 (12%, 5 proximal colon cancers and 3 distal synchronous colon cancers) were detected CRCs), and confirmed at surgery. The surgical proximal to the occlusive cancer in 13 patients. approach and extent in those patients were The accuracy of CTC per patient in the proximal modified after CTC (Table 2). group was 92%; sensitivity, 87%; specificity, 95%; A total of six synchronous carcinomas (9%) PPV, 93%; and NNV, 91%. Per lesion, the were confirmed: three in the colon proximal to the sensitivity of CTC was 100% for polyps at least 10 occlusion and three distal to the occlusion. All of mm in diameter and 88% for polyps at least 6 mm them were correctly diagnosed preoperatively by in diameter. CTC. Sixteen lesions (including 3 synchronous After CTC, the surgeons changed the initial colorectal cancers) were detected distal to the surgical plan in 11 cases (16%), 3 proximal Table 2. Clinically Significant Localization Errors by Colonoscopy Patients Colonoscopic Localization CTC Localization 1 Transverse colon Cecum 2 Mid transverse colon Proximal transverse colon 3 Distal transverse colon Distal ascending colon 4 Splenic flexure Proximal sigmoid colon 5 Descending colon Distal transverse colon 6 Distal descending colon Mid sigmoid colon 7 Sigmoid colon Splenic flexure 8 Mid rectum Rectosigmoid junction Fig. 2. A 44-year-old woman with proven cecal cancer. This occlusive lesion was initially thought to be in the transverse colon by the endoscopist. Three-dimensional surface rendering of the colon (A) and 2-dimensional coronal reformation (B) revealed a large fungating mass (arrows) in the cecum. Yonsei Med J Vol. 48, No. 6, 2007 Joo Hee Kim, et al. A B C D Fig. 3. A 45-year-old man with occlusive colon cancer in the splenic flexure (arrows) with a synchronous colon cancer in the mid transverse colon (arrowheads). (A) The virtual double-contrast display demonstrates an annular circumferential mass in the splenic flexure and a synchronous polypoid cancer in the mid transverse colon, proximal to the occlusion. (B) The transverse CT image and (C) endoluminal CT colonographic image clearly shows this synchronous malignant polyp. (D) Surgical extent was modified to an extended left hemicolectomy to include this synchronous lesion, which could not be identified by CC. synchronous carcinomas and 8 clinically significant appointing accuracies in nodal staging, with a localization errors by CC. range of 22-73%. The accuracy of T staging by CT is also not satisfactory, ranging from 53 to 12-16 77%. Recent multi-detector row CT (MDCT) scanners allow thinner collimation, resulting in DISCUSSION marked improvement of scanning resolution. At present, CT is regarded as a routine pro- Accordingly, MDCT with virtual endoscopy cedure for preoperative evaluation in patients and/or multiplanar reformation could improve 10-12 suspected of having advanced CRC. Mauchley the accuracy of preoperative staging, up to 83- 17-19 et al. suggested that routine preoperative CT 95% in T staging and 80-85% in N staging. provides information that definitely alters treat- In our study, the accuracy of T staging was 86%, ment in 16% patients and is cost-effective. which is comparable but not superior to However, previous studies have shown dis- previous MDCT results. According to the 6th Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas international TNM classification, a tumor per- was inaccurate for tumor localization in 21% of forating the visceral peritoneum is newly occlusive CRC cases, and there were clinically classified into T4. To our knowledge, there have significant localization errors in 11% of occlusive been no reports about CT accuracy in staging CRC cases that required modification of surgical using this new classification. The visceral approach. peritoneum is a thin serous membrane that is Accurate tumor localization for rectal carcinomas not clearly defined in normal CT conditions, also has substantial clinical importance for which probably lowered the CT accuracy in our preventing the inappropriate use of adjuvant study. therapy and determining the proper surgery, Total large bowel evaluation is important in such as segmental sigmoid resection, low anterior planning the treatment of patients with CRC resection, or abdominoperineal resection. because synchronous adenomas and adenocar- Preservation of the anal sphincter is dependent cinomas are found in 14-48% and 2-9% of such on the distance between the lower edge of the 20-28 cases, respectively. Although colonoscopy is tumor and the external sphincter and levator ani regarded as the gold standard for the evaluation muscle. According to a surgery textbook, the of the colon for colorectal tumors, it may be rigid proctosigmoidoscope is recommended for incomplete due to tumor obstruction, which is a measuring the distance of the lower edge of the 4,29 frequent event in distal cancers. There have tumor, because the flexible sigmoidoscope is not been some efforts to evaluate the whole colon as accurate for this determination. In our proximally to an occlusion using imaging opinion, CTC may provide an objective measure- 7-9 modalities, including CTC and MR colonography ment of the distance of the tumor from the anal 30-32 (MRC). The results of both CTC and MRC in verge, which is mandatory for rectal surgery. occlusive CRC are encouraging and evaluation of Further study is necessary to prove this the whole colon by CTC or MRC is reportedly hypothesis. effective. Most reports focus on ‘distal’ occlusive CTC can provide knowledge of whole colorectal 7,9,32 CRC and indicate that CTC (and/or MRC) is lesions, accurate tumor localization and tumor useful in that setting. extent, tumor/nodal staging, and extra-colic The utility of CTC in ‘proximal’ occlusive colon abnormalities, which are critical for the proper cancer remains controversial, because the management of patients with CRC. As a result, majority of advanced right colon cancer cases CTC may become a modality of choice for require classical or extended right hemi- preoperative evaluation of all colorectal cancers. colectomy. We believe that CTC can play an In conclusion, CTC is useful not only for important role even in proximal occlusive colon evaluation of the proximal bowel in occlusive cancer since proximal occlusive colon cancer CRC, but also for accurate staging and tumor detected by CC may not be actual proximal localization, which is informative for the surgeon. colonic lesions. We observed many cases in CTC is recommended when endoscopists encounter which lesions thought to be in the proximal colon occlusive CRC, regardless of tumor location. were actually distal colonic lesions. Among eight clinically significant localization errors, five were located in the proximal colon. There are some REFERENCES reports that CC has a considerable error rate for localization of CRC and is inaccurate in 11-21% 1. Nelson DB, McQuaid KR, Bond JH, Lieberman DA, 33-36 of cases. Anatomic variation and the absence Weiss DG, Johnston TK. Procedural success and complications of large-scale screening colonoscopy. of fixed internal landmarks make it difficult to Gastrointest Endosc 2002;55:307-14. localize the tumor accurately. Furthermore, in 2. Cirocco WC, Rusin LC. Factors that predict incomplete occlusive colon cancer, tumor localization may be colonoscopy. Dis Colon Rectum 1995;38:964-8. more difficult, even for experienced endoscopists, 3. 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Incomplete Colonoscopy in Patients with Occlusive Colorectal Cancer: Usefulness of CT Colonography According to Tumor Location

Kim, Joo Hee; Kim, Won Ho; Kim, Tae Il; Kim, Nam Kyu; Lee, Kang Young; Kim, Myeong-Jin; Kim, Ki Whang
Yonsei Medical Journal , Volume 48 (6) – Dec 31, 2007
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Abstract

Yonsei Med J 48(6):934-941, 2007 DOI 10.3349/ymj.2007.48.6.934 Incomplete Colonoscopy in Patients with Occlusive Colorectal Cancer: Usefulness of CT Colonography According to Tumor Location 1 2 2 3 3 1 Joo Hee Kim, Won Ho Kim, Tae Il Kim, Nam Kyu Kim, Kang Young Lee, Myeong-Jin Kim, and Ki Whang Kim 1 2 3 Department of Radiology, Division of Gastroenterology, Department of Internal Medicine, Department of Surgery, Yonsei University College of Medicine, Seoul, Korea. Purpose: We sought to evaluate the clinical usefulness of Key Words: CT colonography, colorectal neoplasms, staging, CT colonography (CTC) after incomplete conventional colonic obstruction colonoscopy (CC) for occlusive colorectal cancer (CRC) according to the tumor location. Materials And Methods: Seventy-five patients with occlusive CRC underwent subsequent CTC immediately after incomplete CC. Fifty-nine INTRODUCTION patients had distal CRC and 16 had proximal colon cancer. Experienced radiologists prospectively analyzed the location, Conventional colonoscopy (CC) is the current length, and TNM staging of the main tumor. The colorectal standard technique for evaluating the entire polyps in the remaining colorectum and additional ex- colon. Full colonic evaluation is especially traluminal findings were also recorded. Sixty-seven patients important in patients with colorectal malignancy underwent colorectal resection. We retrospectively analyzed because of the high prevalence of synchronous the surgical outcome and correlated CTC and CC findings. adenomas and carcinomas. At the same time, CC Results: The overall accuracies of tumor staging were: T staging, 86%; N staging (nodal positivity), 70% (80%); and fails to show the entire colon in about 6-26% of intra-abdominal M staging, 94%. Additional colonic polyps cases, mainly due to occlusive colorectal cancer 1-4 were found in 23 patients. Six synchronous carcinomas were (CRC). About 15% of patients with CRC detected (9%); three in the proximal colon and three in the present with large bowel obstruction. In this distal colon of occlusion. Clinically significant localization situation, double-contrast barium enema (DCBE) errors at CC were noted in 8 patients (12%, 5 proximal colon might be the next choice for complete evaluation cancers and 3 distal CRCs) and were corrected by CTC. After 5,6 of the proximal colon. This method may be CTC, the surgeons modified the initial surgical plan in 11 limited, however, by poor coating of the cases (16%). Conclusion: In occlusive CRC, CTC is not only useful in the evaluation of the proximal bowel, but can also distended proximal bowel, low accuracy in provide surgeons with accurate information about staging and detecting small polyps, and a problem of residual tumor localization. CTC is recommended when endoscopists barium during surgery. Currently, computed encounter occlusive CRC, regardless of tumor location. tomography colonography (CTC) is regarded as a promising technique for complete evaluation of the proximal colon and simultaneous assessment 7-9 of extraluminal status. Received May 21, 2007 Several reports discuss the usefulness of CTC Accepted July 6, 2007 This work was supported by Yonsei University Research Fund immediately after incomplete CC due to occlusive of 2004. CRC, and most focus on cases of distal colon or Reprint address: requests to Dr. Joo Hee Kim, Department of rectal carcinoma. These promising results have Diagnostic Radiology, Yonsei University College of Medicine, 612 promoted CTC as a choice for preoperative Eonjuro, Gangnam-gu, Seoul 135-720, Korea. Tel: 82-2-2019-3510, evaluation after incomplete CC due to distal Fax: 82-2-3462-5472, E-mail: [email protected] Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas occlusive CRC. However, to our knowledge, no mide), room air was carefully insufflated using a report has documented the usefulness of CTC manual balloon pump through a rectal enema according to tumor location, particularly for tube according to the patient's tolerance. Air proximal occlusive colon cancers. The aim of this filling and distension of the colon were evaluated study was to evaluate the clinical usefulness of on the CT scout before CTC. Once bowel distention CTC in cases of incomplete CC due to occlusive was adequate, CTC was performed after power CRC and to compare the results of CTC in injection of 120 mL (3mL/sec; scanning delay, 60 proximal versus distal occlusive CRCs. sec) of an iodinated IV contrast agent. Two sets of images, one obtained with the patient supine and the other with the patient prone, were MATERIALS AND METHODS generated. CT parameters included 4× 2-mm detector collimation, 120kV, 150-200 mAs, and a Patients pitch of 1.25. Axial CT images were reconstructed as 3-mm slices with a 1.5-mm reconstruction From Mar 2002 to Feb 2004, 75 patients with interval. CT images were transferred to a remote occlusive CRC underwent subsequent CTC PC-based workstation using commercially available immediately after incomplete CC. Experienced software (Rapidia; Infinitt). The processed images internists with gastrointestinal subspecialty training included multiplanar reformatted, ray-sum, and performed CC. Bowel cleansing was provided by virtual colonoscopy images. ingesting 4 L of a polyethylene glycol electrolyte solution in a standard manner before the Image analysis procedure. Initially, the patients were divided into The experienced gastrointestinal radiologist two groups according to the colonoscopic finding: proximal colon cancer (cancer from the cecum to prospectively analyzed tumor localization (tumor splenic flexure) and distal colon and rectal cancer location and the length of the involved segment), (descending-sigmoid colon cancer, rectosigmoid, and TNM staging of the main tumor, using TNM and rectal cancer, but not anal cancer). The classification in the 6th edition of the AJCC and occlusion site, cause of occlusion, and size and UICC system for rating cancer of the colon and the rectum from 2002 (Sobin and Wittekind, 2002). number of other colorectal polyps distal to the occlusion were recorded. Colorectal polyps in the remaining colorectum Seven patients with peritoneal dissemination of proximal and distal to the obstruction were the malignancy and one patient with extensive assessed. Additional extraluminal findings were hepatic metastasis were excluded. Ultimately, 67 also recorded. Postoperative CC was performed to patients (14 proximal and 53 distal occlusive CRC) control the CTC findings in the proximal part of the colon (n=35). with 73 histopathologically proven carcinomas were included in this study, consisting of 45 men Surgical resection was performed after multi- and 22 women (mean age of 58.2 years with a disciplinary team planning with surgeons, in- range of 19-86 years). Informed consent was ternists, and a radiologist. We retrospectively obtained from all patients and all examinations analyzed the surgical outcome and correlated were performed in accordance with the recom- CTC findings with the histopathologic findings and preoperative/postoperative CC results, in- mendations of our institutional review board. Follow-up CC was carried out in 37 patients with cluding the accuracy of CTC for TNM staging (n surgically treated occlusive CRC. =73), accuracies of CTC and CC in localization of the main tumor (n =67), and accuracies of CT protocol CTC and CC in polyp detection, distal (n=75) versus proximal (n=35) to the obstruction. In polyp detection by CTC, sensitivity, specificity, CTC was performed with a 4-channel multi- detector row CT scanner (GE medial; LightSpeed). positive predictive value (PPV), and negative After injection of buscopan (hyoscine n-buthylbro- predictive value (NPV) of CTC were calculated, Yonsei Med J Vol. 48, No. 6, 2007 Joo Hee Kim, et al. per person and per lesion. central nodal metastasis (n=3) (2 had multifocal lesions). A small, subcapsular hepatic metastasis was found that was missed on CT. Small metastatic RESULTS para-aortic nodes in another patient were also missed on CT preoperatively. In determination of Complete CTC examination was achieved in all peritoneal dissemination, one patient was over- 75 patients who underwent CTC immediately staged and one was under-staged. after incomplete CC due to occlusive colon cancer. In 14 patients (21%, 6 proximal colon cancers Sixteen patients had proximal colon cancer and 59 and 8 distal CRCs), the exact site of the cancer patients had distal CRC. Seventy-three adenocar- was initially misdiagnosed on CC. Localization cinomas were retrieved from 67 patients. On histopathological examination, 12 of 73 tumors (16%) were staged as pT1/2, 53 (73%) as pT3, and 8 (11%) as pT4; 28 of 73 (38%) were staged as pN0, 27 (37%) as pN1, and 18 (25%) as pN2; and 56 of 67 (84%) were staged as intra-abdominal pM0 and 11 (16%) as pM1. The overall accuracies of TNM staging on CTC were T staging, 86%; N staging, 70%; and intra- abdominal M staging, 94% (Table 1). The overall accuracy for prediction of pericolic fat infiltration was 96%. In advanced CRC ( pT3), overstaging and understaging occurred in three and four patients, respectively. These cases were all incor- rectly interpreted as to whether the tumor Fig. 1. A 39-year-old woman with mid transverse colon perforated the visceral peritoneum (T4) or not cancer. Axial CT scan reveals irregular wall thickening (T3). The overall accuracy for prediction of nodal with luminal narrowing of the transverse colon with pericolic fat infiltration (arrow). The visceral peritoneum positivity (involved or tumor-free) was 80%. was not identifiable and no solid organ invasion was Intra-abdominal metastatic lesions were found in visible, which suggested stage T3. However, the 11 patients: 4 liver metastasis (n=4), peritoneal pathologic stage of this lesion proved to be pT4 because dissemination of the malignancy (n=6), and of tumor invasion into the visceral peritoneum. Table 1. Pathologic and CTC Staging of TNM CTC staging Pathologic staging T1/T2 T3 T4 N0 N1 N2 M0 M1 T (n=73) T1/T2 12 9 3 T3 53 50 3 T4 8 4 4 N (n=73) N0 28 16 9 3 N1 27 2 20 5 N2 18 1 2 15 M (n=67) M0 56 55 1 M1 11 3 8 Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas errors were clinically insignificant in six of the occlusive cancer in 12 patients. The accuracy of patients, and the planned operations were carried CTC per patient in the distal group was 96%; out without modification. Clinically significant sensitivity, 83%; specificity, 98%; PPV, 92%; and localization errors were noted in eight patients NNV, 97%. Forty-two abnormalities (including 3 (12%, 5 proximal colon cancers and 3 distal synchronous colon cancers) were detected CRCs), and confirmed at surgery. The surgical proximal to the occlusive cancer in 13 patients. approach and extent in those patients were The accuracy of CTC per patient in the proximal modified after CTC (Table 2). group was 92%; sensitivity, 87%; specificity, 95%; A total of six synchronous carcinomas (9%) PPV, 93%; and NNV, 91%. Per lesion, the were confirmed: three in the colon proximal to the sensitivity of CTC was 100% for polyps at least 10 occlusion and three distal to the occlusion. All of mm in diameter and 88% for polyps at least 6 mm them were correctly diagnosed preoperatively by in diameter. CTC. Sixteen lesions (including 3 synchronous After CTC, the surgeons changed the initial colorectal cancers) were detected distal to the surgical plan in 11 cases (16%), 3 proximal Table 2. Clinically Significant Localization Errors by Colonoscopy Patients Colonoscopic Localization CTC Localization 1 Transverse colon Cecum 2 Mid transverse colon Proximal transverse colon 3 Distal transverse colon Distal ascending colon 4 Splenic flexure Proximal sigmoid colon 5 Descending colon Distal transverse colon 6 Distal descending colon Mid sigmoid colon 7 Sigmoid colon Splenic flexure 8 Mid rectum Rectosigmoid junction Fig. 2. A 44-year-old woman with proven cecal cancer. This occlusive lesion was initially thought to be in the transverse colon by the endoscopist. Three-dimensional surface rendering of the colon (A) and 2-dimensional coronal reformation (B) revealed a large fungating mass (arrows) in the cecum. Yonsei Med J Vol. 48, No. 6, 2007 Joo Hee Kim, et al. A B C D Fig. 3. A 45-year-old man with occlusive colon cancer in the splenic flexure (arrows) with a synchronous colon cancer in the mid transverse colon (arrowheads). (A) The virtual double-contrast display demonstrates an annular circumferential mass in the splenic flexure and a synchronous polypoid cancer in the mid transverse colon, proximal to the occlusion. (B) The transverse CT image and (C) endoluminal CT colonographic image clearly shows this synchronous malignant polyp. (D) Surgical extent was modified to an extended left hemicolectomy to include this synchronous lesion, which could not be identified by CC. synchronous carcinomas and 8 clinically significant appointing accuracies in nodal staging, with a localization errors by CC. range of 22-73%. The accuracy of T staging by CT is also not satisfactory, ranging from 53 to 12-16 77%. Recent multi-detector row CT (MDCT) scanners allow thinner collimation, resulting in DISCUSSION marked improvement of scanning resolution. At present, CT is regarded as a routine pro- Accordingly, MDCT with virtual endoscopy cedure for preoperative evaluation in patients and/or multiplanar reformation could improve 10-12 suspected of having advanced CRC. Mauchley the accuracy of preoperative staging, up to 83- 17-19 et al. suggested that routine preoperative CT 95% in T staging and 80-85% in N staging. provides information that definitely alters treat- In our study, the accuracy of T staging was 86%, ment in 16% patients and is cost-effective. which is comparable but not superior to However, previous studies have shown dis- previous MDCT results. According to the 6th Yonsei Med J Vol. 48, No. 6, 2007 CT Colonography in Occlusive Colorectal Carcinomas international TNM classification, a tumor per- was inaccurate for tumor localization in 21% of forating the visceral peritoneum is newly occlusive CRC cases, and there were clinically classified into T4. To our knowledge, there have significant localization errors in 11% of occlusive been no reports about CT accuracy in staging CRC cases that required modification of surgical using this new classification. The visceral approach. peritoneum is a thin serous membrane that is Accurate tumor localization for rectal carcinomas not clearly defined in normal CT conditions, also has substantial clinical importance for which probably lowered the CT accuracy in our preventing the inappropriate use of adjuvant study. therapy and determining the proper surgery, Total large bowel evaluation is important in such as segmental sigmoid resection, low anterior planning the treatment of patients with CRC resection, or abdominoperineal resection. because synchronous adenomas and adenocar- Preservation of the anal sphincter is dependent cinomas are found in 14-48% and 2-9% of such on the distance between the lower edge of the 20-28 cases, respectively. Although colonoscopy is tumor and the external sphincter and levator ani regarded as the gold standard for the evaluation muscle. According to a surgery textbook, the of the colon for colorectal tumors, it may be rigid proctosigmoidoscope is recommended for incomplete due to tumor obstruction, which is a measuring the distance of the lower edge of the 4,29 frequent event in distal cancers. There have tumor, because the flexible sigmoidoscope is not been some efforts to evaluate the whole colon as accurate for this determination. In our proximally to an occlusion using imaging opinion, CTC may provide an objective measure- 7-9 modalities, including CTC and MR colonography ment of the distance of the tumor from the anal 30-32 (MRC). The results of both CTC and MRC in verge, which is mandatory for rectal surgery. occlusive CRC are encouraging and evaluation of Further study is necessary to prove this the whole colon by CTC or MRC is reportedly hypothesis. effective. Most reports focus on ‘distal’ occlusive CTC can provide knowledge of whole colorectal 7,9,32 CRC and indicate that CTC (and/or MRC) is lesions, accurate tumor localization and tumor useful in that setting. extent, tumor/nodal staging, and extra-colic The utility of CTC in ‘proximal’ occlusive colon abnormalities, which are critical for the proper cancer remains controversial, because the management of patients with CRC. As a result, majority of advanced right colon cancer cases CTC may become a modality of choice for require classical or extended right hemi- preoperative evaluation of all colorectal cancers. colectomy. We believe that CTC can play an In conclusion, CTC is useful not only for important role even in proximal occlusive colon evaluation of the proximal bowel in occlusive cancer since proximal occlusive colon cancer CRC, but also for accurate staging and tumor detected by CC may not be actual proximal localization, which is informative for the surgeon. colonic lesions. 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Yonsei Medical Journal – Pubmed Central

Published: Dec 31, 2007

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