Colonoscopy Inaccurate for Cancer Site In Nearly One-Third of Cases

The location of colon cancers determined by colonoscopy does not agree with the surgical location in almost one-third of cases, researchers have found. The problem is particularly acute for right-sided lesions, according to the study, which was presented at the 2016 Digestive Disease Week (abstract Su1623). Colonoscopy is a valuable tool not only to screen for and diagnose colorectal cancer but for localization and surveillance of tumors. The location of a tumor in the colon also guides the course of therapy with surgery, radiation or both. “Colon cancer resections are often guided by endoscopic localization,” said Jennifer Nayor, MD, of the Division of Gastroenterology, Hepatology and Endoscopy at Brigham and Women’s Hospital and Harvard Medical School, both in Boston, and co-author of the study. “Colon cancer resections are more frequently performed by a laparoscopic approach, where surgeons lose the opportunity to directly palpate the colon to ensure the correct area is being resected. If endoscopists are not accurately localizing lesions, there is the potential for flawed surgical planning and intraoperative changes to surgical procedures.” Dr. Nayor and her colleagues conducted a retrospective cohort study of patients diagnosed with colon cancer. Data were obtained on the participants’ endoscopic and surgical reports and tumor characteristics. During the study period, there were 203 cases of colon cancer and 110 cases with a colonoscopy that occurred within six months of the diagnosis. Overall, in 31% of the cases (34/110), the endoscopic location did not match the surgical location. Nearly 30% of the cases (n=10) were inaccurate by a colonic segment. For the study, colonic segments were defined as the cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, the rectosigmoid junction and the rectum. Two cases identified by surgery as right-sided tumors were initially diagnosed as left-sided tumors by colonoscopy. Right-sided colon lesions were associated with increased risk for discordance compared with left-sided lesions, on both univariate and multivariate analyses (odds ratio, 1.83; P=0.04). “Our multicenter study showed that over 30% of colon cancers were inaccurately localized by colonoscopy compared to the gold standard of surgical localization. The only predictor of inaccurate endoscopic localization was right-sided colon cancer,” Dr. Nayor told Gastroenterology & Endoscopy News. The findings underscore the importance of using anatomic landmarks for localization during endoscopy, she added, as well as tattooing to guide intraoperative localization. “Surgeons should be aware of the issue of inaccurate endoscopic localization, so they can discuss this with patients when consenting for procedures,” she pointed out. Deborah Fisher, MD, MHS, associate professor of medicine in the Division of Gastroenterology at Duke University School of Medicine, in Durham, N.C., said with few landmarks inside the colon, estimates of location based on measurement from the anal verge may be inaccurate. “The location of the tumor can impact the surgical plan and approach,” said Dr. Fisher, who was not involved with the latest study. “A more extensive operation could result if the tumor is not near—not more than two or more segments away from—the expected location.” Location is particularly important for rectal or rectosigmoid tumors, she added. Dr. Fisher noted that the cases of right-sided lesions mistaken for left-sided ones are the “most concerning” finding in the study. The results support the use of confirmation of cecal location with cecal intubation to help avoid mistaking a right-sided lesion for a left-sided one and the use of tattoo marking of the tumor, she said.