Sigmoidoscopy curbs colon cancer risk and death for men, not women

Last Updated: 2018-04-23

By Marilynn Larkin

NEW YORK (Reuters Health) - Sigmoidoscopy screening in Norway reduced colorectal cancer (CRC) incidence and death in men but had little effect in women, researchers say.

Dr. Oyvind Holme of the University of Oslo and colleagues analyzed data from 1999 through 2001 on 20,552 individuals ages 50-64 randomly assigned to CRC screening with flexible sigmoidoscopy with or without fetal occult blood testing (FOBT) versus 78,126 individuals assigned to no screening.

During sigmoidoscopy, any detected polyps were removed or biopsied and examined histologically. A positive result on a screening test was defined as any polyp 10 mm or larger, an adenoma, CRC, or positive findings on FOBT.

As reported online April 23 in Annals of Internal Medicine, adherence rates were 64.7% for women and 61.4% for men, and median followup was 14.8 years.

The absolute risks for CRC in women were 1.86% in the screening group and 2.05% in the control group (HR, 0.92). CRC incidence rates differed little between the screening and control groups when analyzed by tumor location (distal vs. proximal colon) or screening method (sigmoidoscopy alone vs. with FOBT).

The 15-year risks for CRC death in women were 0.60% in the screening group and 0.59% in the control group.

By contrast, in men, the absolute risks for CRC were 1.72% in the screening group and 2.50% in controls (HR, 0.66).

The HRs for men were 0.59 for cancer in the distal colon and 0.81 for cancer in the proximal colon. The CRC incidence rate was lower in the screening group than in the control group for both older and younger age groups and for sigmoidoscopy with and without FOBT.

The 15-year risks for CRC death in men were 0.49% in the screening group and 0.81% in the control group (HR, 0.63). The HRs were 0.65 for death from CRC of the distal colon and 0.60 for the proximal colon.

For sigmoidoscopy screening alone in men, the HR was 0.64 compared with 0.62 for sigmoidoscopy with FOBT.

"Even if sigmoidoscopy is not a popular screening method in many countries, our study shows that it is a valuable screening tool for men, reducing both incidence and mortality from colorectal cancer," Dr. Holme told Reuters Health.

"It only takes on average five minutes," he said by email, "and the effect is, according to our results, long lasting."

"For women, however, other screening tools should be considered," he added. "The results from this study tell us that research is still needed in the area of colorectal cancer screening."

"We should not introduce screening in the population that is not evidence-based," Dr. Holme concluded.

Dr. Kirsten Bibbins-Domingo of University of California, San Francisco, coauthor of a related editorial, told Reuters Health, "Despite clear evidence of effectiveness for several different approaches to colon cancer screening, more than one third of men and women are not up-to-date with any of these approaches."

"Screening with one of these recommended approaches lowers the chance of getting colon cancer and dying of colon cancer," she said by email.

"The most important message for clinicians and patients - both men and women - is to pick an approach to screening among the several supported by evidence and to stick to it consistently," she said.

"Sigmoidoscopy screening is currently recommended every five years, or 10 years when combined with annual fecal immunochemical testing," she continued.

"The new study suggests that men may be able to screen with sigmoidoscopy less frequently - in fact, the study suggests that a single screen may be effective for 15-17 years," she continued. "That's important because it may increase adherence in men for this particular strategy."

"However, this single screen did not seem to be effective in women so is probably not the best choice for them," Dr. Bibbins-Domingo concluded.

SOURCE: http://bit.ly/2HUoXIK

Ann Intern Med 2018.