Colorectal cancer risk remains low 17 years after single negative screening colonoscopy

Last Updated: 2020-05-26

By Will Boggs MD

NEW YORK (Reuters Health) - The incidence and mortality of colorectal cancer (CRC) remain low 17 years after a single negative screening colonoscopy, researchers in Poland report.

"Our findings confirm that a 10-year interval between high-quality screening colonoscopies is safe and there is no benefit from more frequent screening," said Dr. Nastazja Dagny Pilonis from The Maria Sklodowska-Curie National Research Institute of Oncology and the Medical Center for Postgraduate Education, in Warsaw.

"Furthermore, the findings suggest that this interval could even be prolonged, provided that baseline colonoscopy is high-quality," she told Reuters Health by email.

Current clinical practice guidelines recommend screening colonoscopies at 10-year intervals in the average-risk population when results are negative, but some studies suggest that the predictive benefit of a single negative colonoscopy may exceed 10 years.

Dr. Pilonis and colleagues used data from the Polish Colonoscopy Screening Program to analyze the long-term CRC incidence and mortality of more than 165,000 average-risk individuals who had a single negative screening colonoscopy.

Among these persons, 113,513 had low-quality colonoscopy and 52,374 had high-quality colonoscopy, which was defined by the combination of cecal intubation, adequate bowel preparation and annual endoscopic adenoma detection rate of 20% or greater.

During follow-up of up to 17.4 years (median, 10.1 years), the cumulative incidence rate was 29.09 cases per 100,000 person-years and the CRC-related mortality rate was 10.05 deaths per 100,000 person-years, the researchers report in the Annals of Internal Medicine.

Compared with the general population, the CRC incidence was 72% lower and CRC mortality was 81% lower, both significant reductions, with similar reductions in incidence and mortality beyond 10 years of follow-up (69% and 73%, respectively) and between 5.1 and 10 years (70% and 79%, respectively).

The CRC incidence and mortality were significantly lower after high-quality colonoscopy than after low-quality examination.

Overall, the incidence and mortality rates from CRC differed significantly between men and women, but these differences were not observed after high-quality examination.

The incidence of proximal CRC was reduced by 73% after high-quality screening, but by only 45% after low-quality screening; the mortality of proximal CRC was also lower after high-quality screening than after low-quality colonoscopy (50% lower vs. 8% lower, respectively).

"Our findings on the risk of proximal CRC and death from proximal CRC are surprising," Dr. Pilonis said. "Previous studies had questioned the efficacy of colonoscopies in the proximal colon as opposed to the distal colon. We found that high-quality colonoscopy results in not only lower risk of proximal CRC incidence, but also reduced mortality from proximal CRC. This reduction was not seen after low-quality colonoscopies."

"We showed that high-quality is a prerequisite for safe intervals between colonoscopies," Dr. Pilonis concluded. "All endoscopists should strive to deliver high-quality screening colonoscopies, in particular ensuring that their adenoma detection rate (ADR) is adequate (each component of high-quality examination - cecal intubation, adequate bowel preparation, and ADR of 20% or greater - contributes to the observed colonoscopy efficacy, with ADR being most important)."

Dr. Jeffrey K. Lee of Kaiser Permanente San Francisco, in California, who recently reported low rates of CRC and CRC-related death 12 years after a colonoscopy with normal findings, told Reuters Health by email, "These findings suggest that physicians should feel confident following the guideline-recommended 10-year rescreening interval after a normal colonoscopy. In addition, this study further supports the importance of a high-quality colonoscopy for extending the rescreening interval to greater than 10 years."

"This study provides additional evidence that the quality of the colonoscopy is important in reducing your risk of colorectal cancer," said Dr. Lee, who was not involved in the research.

SOURCE: https://bit.ly/2TBEzrR Annals of Internal Medicine, online May 26, 2020.