Incompletely Removed Colon and Rectal Polyps Often Recur

A polyp is a tissue growth arising from a surface in the body, usually within an organ’s cavity. Polyps are most commonly found in the colon and rectum, which are parts of the large intestine, as well as in the ear canal and cervix.

Large intestine (colon and rectal) cancers begin when some benign adenomas and polyps become malignant over time. The risk of cancer is higher when polyps are large or multiple. With screening methods such as colonoscopy, polyps can be detected early and the incidence of colorectal cancer can be reduced.

Colorectal (large intestine) polyps are slow-growing formations arising from the mucosa, the innermost layer of the large intestine, with a low risk of becoming cancerous ( < % 1 ). However, these polyps are very common in the population, and their frequency increases with age. Polyps create a significant predisposition to colorectal cancer and should therefore be removed when detected.

Incompletely Removed Colorectal Polyps

In some cases, gastroenterologists may unknowingly leave behind some neoplastic tissue (cells forming the tumor) when removing polyps during colonoscopy. Research has shown that biopsies taken from resection (removal) margins sometimes contain residual polyp tissue even after the lesion has visibly been removed. However, the significance of incomplete resection is unclear.

A study comparing incomplete and complete resection showed that the likelihood of finding polyps during follow-up colonoscopy increased significantly after incomplete colonoscopy. Dr. Heiko Pohl, who took part in the study, said that the evidence strongly supports the hypothesis that residual polyp tissue causes recurrence of neoplastic polyps and, consequently, possibly colorectal cancer.

Among 166 participants in the Complete Adenoma Resection (CARE) study who continued follow-up colonoscopies in subsequent years, synchronous neoplasia (tumor formation) was detected more frequently in colon segments where polyps had not been completely removed than in segments with complete resection (52% vs. 23%).

In addition, colon segments with incomplete resections in the CARE study were more likely to have polyps measuring 10 mm or larger (18% vs. 3%). The 32 participants who had at least one incomplete resection during the study were also found to be three times more likely to have polyps at follow-up. However, there were no cases of cancer or high-grade dysplasia during follow-up.

Dr. Shai Freidland, Professor of Gastroenterology and Hepatology at Stanford University, who was not involved in the study, said: “Why do people get cancer after colonoscopy? Perhaps it is because of these polyps that were not completely removed.” Friedland said that, although it is not surprising for residual polyp tissue to appear as polyps at follow-up examinations, the difference in polyp recurrence between the groups would have to be “quite striking” for it to be clearly evident in this small study. The results indicate a need for "doubling our efforts to make sure we completely remove polyps, rather than just hoping they disappear after an incomplete job" in clinical practice.

In the CARE study, conducted at two academic medical centers between 2009 and 2012, researchers found that approximately 10% of neoplastic polyps that had visibly been completely removed were nevertheless incompletely resected, based on the presence of neoplastic tissue in biopsies taken from the resection margins.

The researchers focused on nonpedunculated (sessile) colorectal polyps measuring 5 to 20 mm removed during routine polypectomy using electrocautery. Participants with incomplete polyp resection were encouraged to have a follow-up examination within 1 year, while those with complete resections were given guideline-based follow-up recommendations. In the follow-up analysis, the median time to the first examination was 17 months for those with incomplete resection and 45 months for those with complete resection.

“These results emphasize the importance of achieving complete resection, because without it, the risk of subsequently detecting advanced neoplasia increases statistically significantly. Large polyp size after incomplete resection, within an overall short follow-up period, may imply rapid growth, even though none of the presumed recurrent polyps had advanced histological features.”

The researchers noted that differences within the groups in participants and polyps could confound the observations. Because of the initial study findings, endoscopists performing follow-up colonoscopies may have looked more carefully for polyps in colon segments with previous incomplete resections. In addition, although detection and resection skills are not correlated, it seems possible that endoscopists were more likely to miss polyps in people with a greater proportion of incomplete resections, with those polyps detected at later follow-up.

Friedland said that the goal of resection is to remove a polyp in one piece together with its margins, but that researchers know polyp-removal techniques are “not perfect.” He said this raises the question of whether the field should focus on improving standard techniques or incorporate newer, more advanced approaches such as endoscopic submucosal dissection, which is effective but carries a significant risk of perforation when performed by nonspecialists.

Pohl said, “One of our main focuses over the years has been finding polyps to prevent potential cancer. But the CARE study showed that we are not doing a good job of completely removing polyps.” He emphasized that specialists should do their best to remove polyps completely, even if there is no way to verify complete resection in routine practice. Specialists should also aim to improve their skills and techniques. Pohl also suggested that expert-guided video assessments may help. “We need to think very seriously about assessing the quality of the work being done,” he said.