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Colorectal cancer was rarely detected via surveillance colonoscopies in older adults regardless of prior adenoma finding, a large observational study found.

Among 9,601 patients ages 70 to 85 with a history of adenoma, 0.3% of surveillance colonoscopies found colorectal cancer, while 11.7% found advanced adenoma, and 12% found advanced neoplasia. Results did not differ significantly by age, said researchers led by Jeffrey Lee, MD, MPH, of Kaiser Permanente Northern California in Oakland.

Patients with a history of advanced adenoma versus non-advanced were more likely to have colorectal cancer detected by surveillance, though still rarely (0.5% vs 0.2%, P=0.02), and were more likely to have advanced neoplasia (16.5% vs 10.6%, P<0.001), Lee's group reported in .

The findings can help inform whether to continue surveillance colonoscopy in older adults, Lee and co-authors said.

"Given the increasing aging population in the U.S. and that nearly 5.6 million adults older than 75 years will undergo surveillance annually by 2024, estimating the yield of surveillance colonoscopy is important for understanding the balance between potential benefits and known risks of colonoscopy with advancing age," they wrote.

In the U.S., approximately 40% of screening colonoscopies find adenomas, and guidelines recommend patients have surveillance colonoscopy after undergoing polypectomy. However, guidelines don't specify an age at which surveillance is unlikely to be of substantial benefit and could be stopped, Lee and colleagues noted.

Risks associated with colonoscopy increase particularly among patients 75 years or older, and include heart attack, stroke, sedation-related adverse events such as aspiration pneumonia, bleeding, infection, and perforation, Lee's group observed.

"These findings provide some of the first large-scale, community-based information on the yield of surveillance colonoscopy among older adults," they wrote.

They highlighted two key findings that could inform shared decision making about surveillance colonoscopy. First, colorectal cancer was rarely detected among older adults with prior advanced or non-advanced adenomas. "Thus, for many older adults, particularly those with a prior nonadvanced adenoma, the low rate of [colorectal cancer] detection at surveillance may not justify the potential harms and burdens of colonoscopy that may increase with age," the study authors said.

They did note that for older adults with a predicted life expectancy of 10 or more years and without significant competing comorbidities, detecting early-stage colorectal cancer or advanced adenomas at surveillance could lead to earlier treatment and improved outcomes, especially for those with a prior advanced adenoma.

Second, advanced adenoma was more commonly detected than colorectal cancer, however advanced adenomas themselves are not harmful to patients; for the rare lesions that do progress to invasive cancer, the process takes several years. "Thus, among older adults with limited life expectancies due to comorbidities, few would likely benefit from the detection and removal of these polyps," they said.

"With current guidelines offering no specific age at which to stop surveillance colonoscopy, the study findings can inform clinicians and older patients regarding the potential benefits (or lack of benefits) of continuing with post polypectomy surveillance in the context of the life expectancy of the patient and weighed against the rare but known harms of colonoscopy, which increase with advancing age and comorbidities," the researchers concluded.

Agreeing with the researchers, John Carethers, MD, of the University of California San Diego and past president of the , commented this study does not specifically answer the question on the age to stop post-polypectomy surveillance, "but does inform the likelihood of a septa- or octogenarian who has previously had advanced neoplasia is more likely to develop it again, but rarely as cancer."

Carethers, who wasn't involved with the research, told 番茄社区app this study "adds one more piece that was not previously known toward the patient-provider discussion on whether to perform a surveillance colonoscopy, with its increasing risk as one ages, with any benefits in preventing the extremely low risk for subsequent cancer."

The population-based, cross-sectional study included patients 70 to 85 with a history of adenoma. Participants underwent a surveillance colonoscopy from 2017-2019 at Kaiser Permanente Northern California, a large, community-based U.S. healthcare system. Individuals with prior colorectal cancer, hereditary colorectal cancer syndrome, inflammatory bowel disease, or prior colectomy were excluded.

Data were analyzed from 2022-2024. The main outcomes were detection of colorectal cancer, advanced adenoma, and advanced neoplasia overall by age and by prior adenoma finding (advanced vs non-advanced).

An important limitation of the study was its cross-sectional design, the study authors noted. The follow-up time was limited, and colorectal cancer may take many years to develop. In addition, the study population was from a large healthcare system and limited to patients with prior adenoma. The results might not be generalizable to unscreened patients who could be at higher risk, they said.

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