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Adenomatous Polyps and Long-term Risk of Colorectal Cancer

March 18, 2019

New research1 published in JAMA in May 2018 by Robert E. Schoen, MD, MPH, and collaborators from the National Cancer Institute using participants in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer trial of colorectal cancer screening, provide new insights on adenoma findings during colonoscopy and their long-term association with incidence of colorectal cancer (CRC).

Current guidelines in the United States recommend that people with one or two nonadvanced tubular adenomas return for repeat surveillance colonoscopy in five to 10 years. However, there is no guidance about who should return at five, seven, or 10 years, and there has never been a long-term study evaluating the relationship between non-advanced adenomas and colorectal cancer.  Dr. Schoen explains, “Bringing everyone back at five years is incurring a lot of testing that may not be preventing much cancer, because only a small fraction of polyps will ever turn into cancer. Millions of people are receiving follow-up colonoscopy exams for non- advanced polyps. We need to find out what is necessary. Potentially, this is an area where we could reduce testing and costs.”

To determine the risk of developing colorectal cancer after finding polyps, the study looked at data from 15,900 participants who underwent a colonoscopy as a result of their participation in the PLCO trial. At baseline, the researchers found that 2,882 (18.1 percent) of patients had an advanced polyp; 5,068 (31.8 percent) had nonadvanced adenomas; and 7,985 (50.1 percent) had no adenomas. Patients were followed for up to 15 years.

Subjects with advanced adenoma polyps had a 2.7-fold increased long-term risk of colorectal cancer compared to those with no adenomas. In contrast, subjects with nonadvanced adenomas had a colorectal cancer risk that is similar to people in whom no polyps were found.

“This finding concerning nonadvanced adenomas is significant and of interest, because it tells us that we may not have to surveil or follow these patients with repeated colonoscopy as aggressively as we have in the past. This has obvious implications for patients and providers — fewer procedures, less worry, and reduced costs,” says Dr. Schoen.

As a follow-up to this study, Dr. Schoen and colleagues have drafted a proposed randomized trial with NRG Oncology to study nonadvanced adenoma patients over five- and 10-year periods, assessing outcomes and the incidence of cancer.

“We have approvals but have not yet secured funding for such an initiative. It would be a large-scale endeavor, and NCI is still considering it, but we are hopeful we will have the opportunity to explore the long-term implications of clinical practice updates more thoroughly.”


1 Click B, Pinsky PF, Hickey T, Doroudi M, Schoen RE. Association of Colonoscopy Adenoma Findings With Long-Term Colorectal Cancer Incidence. JAMA. 2018; 319(19): 2021-2031.