Spotlight on colorectal cancer screening intervals

Patients with a complete, negative colonoscopy had reduced risk of colorectal cancer for more than 15 years, one study found, while another found that early-onset colorectal cancer doesn't require more frequent follow-up surveillance than average-onset cases.

Two recent studies analyzed colon cancer screening intervals.

The first study, published by The Lancet Gastroenterology & Hepatology on May 15, aimed to estimate how long patients remain at reduced risk of colorectal cancer incidence and mortality after a complete, negative colonoscopy. The population-based cohort study included more than 7 million Canadian patients ages 50 to 65 years between Jan. 1, 1994, to Dec. 31, 2017, with a median follow-up of 12.56 years. Overall, 90,532 (1.7%) patients were diagnosed with colorectal cancer and 44,088 (0.8%) died of colorectal cancer. Compared to those with no complete colonoscopy, risk of colorectal cancer was reduced in patients who had a complete negative colonoscopy within five years, five to 10 years, 10 to 15 years, or less than 15 years, after adjustment for age, sex, comorbidity, income, and immigration status. Even among those who had had a colonoscopy more than 15 years earlier, the risk reduction was significant (hazard ratios [HR], 0.62 [95% CI, 0.51 to 0.77] for women and 0.57 [95% CI, 0.46 to 0.70] for men). Results were similar for colorectal cancer mortality. A colonoscopy with intervention was associated with lower risk for up to 10 years for women (HR, 0.70 [95% CI, 0.63 to 0.77]) and up to 15 years for men (HR, 0.62 [95% CI, 0.53 to 0.72]).

"Our results, examining one of the largest population-based cohorts to date, show that those who receive a complete negative colonoscopy have a lower risk of colorectal cancer incidence and mortality that extends beyond 10 years compared with those who do not have a complete colonoscopy," said the study authors, who suggested reconsideration of current screening guidelines. "In addition to the need to consider more prolonged rescreening intervals, our results also suggest that risk reduction after a complete negative colonoscopy was more pronounced in male individuals than female individuals, which might suggest different strategies are needed by sex."

An accompanying editorial noted several limitations, including lack of data on lifestyle risk factors for colorectal cancer or the indication for and quality of baseline colonoscopy. "An overarching recommendation to extend colonoscopy intervals could, therefore, pose an unacceptable risk for a subset of individuals but will be safe for those individuals who received a high-quality colonoscopy performed by a high quality endoscopist," the editorialists said.

The second study, published by Clinical Gastroenterology and Hepatology on May 8, focused on patients with colorectal cancer diagnosed before age 50 years. It included 1,259 patients with colorectal cancer from one U.S. cancer center; 612 had early-onset cancer (before age 50 years) and 647 had onset at an average age. Average follow-up time from surgical resection to first surveillance colonoscopy was 12.6 months in both groups. However, the early-onset patients had a decreased risk of developing advanced neoplasia between surgery and first surveillance colonoscopy (hazard ratio, 0.71 [95% CI, 0.52 to 1.0]). Fewer early-onset patients had advanced neoplasia on surveillance colonoscopy than average-age patients (12.4% vs. 16.0%). Early-onset patients returned sooner for subsequent surveillance but did not have more cancers, advanced adenomas, or nonadvanced adenomas than older patients.

The study authors noted that there are no surveillance guidelines in the U.S. for patients with early-onset colorectal cancer but that an international group has recommended younger patients undergo surveillance at the same intervals as older patients, which this new evidence supports. The more frequent surveillance seen among younger patients in this study may have negative outcomes such as surveillance fatigue and decreased long-term adherence, as well as increasing health care costs, the authors said. They did note that patients with abnormal findings on surveillance were found to be at higher risk going forward. "Individual and personalized strategies should be adopted for these patients based on the individual's risk profile and clinical history," they wrote.