Interval Colorectal Cancers arising from small, flat Lesions

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Following a 10 year review of patients at a European hospital, it has been concluded that about 2% of all colorectal cancers (CRCs) result from missed lesions or incomplete polypectomy during index colonoscopy. The study, presented at the 2011 Digestive Disease Week meeting in the US, was recognized as one of 10 best of the meeting.

The incidence of interval CRCs is low and estimates vary; three recent studies put the number between 3.4% and 7.9% of all CRCs. Because interval colon cancers occur after patients receive colonoscopy, they are, theoretically, preventable.

“Interval colorectal cancers are relatively uncommon, yet devastating events,” said Silvia Sanduleanu, MD, PhD, a gastroenterologist at Maastricht University Medical Centre in the Netherlands and the study’s senior author. “A substantial proportion can be attributed to errors and it is important to understand this because it is probably correctable.”

Dr. Sanduleanu looked to uncover the rate of interval CRCs in her institution and to understand the factors that might contribute to missed polyps. In particular, she hoped to understand the shapes and appearance of missed polyps that later developed into cancers.

Dr. Sanduleanu’s group reviewed all patients with a CRC diagnosis at Maastricht University Medical Center between 2001 and 2010, excluding those with hereditary CRC syndromes, inflammatory bowel disease, previous CRC diagnosis, and in whom there was incomplete visualization of the colon or inadequate surveillance.

Data were drawn from digital endoscopy and histopathology reports in a national database in the Netherlands and verified through a regional cancer centre’s CRC registry. Interval CRC was defined as a cancer occurring within five years of an index colonoscopy. These cancers were then categorized based on size, macroscopic appearance as either flat or protruded, and location proximal or distal relative to the splenic flexure.

The location of the cancer was also compared with previous polypectomy sites during index colonoscopy; interval cancers found within the same anatomic segment were considered the result of incomplete polypectomy.

In the 10-year study, 1,218 patients, with an average age of 70 years, were diagnosed with CRC. Twenty-eight cases, or 2.2%, were interval cancers and were found an average of 26 months after index colonoscopy.

When the investigators tried to ascertain the cause, 53.6% of interval CRCs were attributed to small or flat missed lesions and 35.7% to incomplete polypectomy during index colonoscopy.
“Generally we think that these incomplete resections are related more commonly with larger lesions,” said Douglas Robertson, MD, MPH, a gastroenterologist at the VA Medical Centre in White River Junction.

However, the study did not include information on the original size of these lesions; the data only revealed that, at the time of interval CRC diagnosis, lesions were “significantly smaller in size, less than 2 cm.”

Because about one in 45 CRCs comes from “overlooked, small or flat neoplasms or incomplete polypectomy,” Dr. Sanduleanu said the main message of her study was to improve education on finding these small, flat lesions and removing them completely.