One-time-only screening for colorectal cancer using flexible sigmoidoscopy reduced colorectal cancer incidence by 20% and colorectal cancer–specific mortality by 27% in a Norwegian study involving more than 20,000 adults followed for approximately 11 years, which was published online Aug. 12 in JAMA.
In addition, younger patients aged 50-54 years appeared to benefit at least as much from screening as older patients aged 55-64 years, in what the investigators described as the first randomized controlled trial to assess the benefit of the procedure in this age group. This finding is particularly important given that some national screening recommendations, including those in the United States, advise that colorectal cancer screening be initiated at age 50 rather than at 55, said Dr. Oyvind Holme of Sorlandet Hospital, Kristiansand, Norway, and his associates in the Norwegian Colorectal Cancer Prevention (NORCCAP) trial.
NORCCAP is a population-based, randomized controlled study in which 100,210 men and women aged 50-64 years residing in two geographic regions in Norway in 1999-2001 were invited by mail to undergo once-only flexible sigmoidoscopy screening or flexible sigmoidoscopy plus fecal occult blood testing (FOBT) for colorectal cancer. Virtually no other screening colonoscopies were available outside this trial in Norway at that time, so it was ensured that members of the control group couldn’t be screened on their own, biasing the study results.
The intent-to-treat population comprised 98,792 adults: 10,283 randomly assigned to flexible sigmoidoscopy, 10,289 randomly assigned to flexible sigmoidoscopy plus FOBT, and 78,220 control subjects. Adherence to screening was 63%, with 12,955 of the invited patients attending their screening exam.
After a median follow-up of 11 years, the incidence of colorectal cancer was 112.6 per 100,000 person-years in the screening group, compared with 141.0 in the control group, a 20% difference. Similarly, colorectal cancer–specific mortality was 31.4 per 100,000 person-years in the screening group, compared with 43.1 in the control group, a 27% difference, the investigators reported (JAMA 2014 312:606-15).
Adding FOBT to flexible sigmoidoscopy not only failed to improve colorectal cancer detection, it was actually a deterrent to adherence, and thus may have impeded detection, Dr. Holme and his associates said.
NORCCAP was funded by the Norwegian government, the Norwegian Cancer Society, the Research Council of Norway, The South-East Regional Health Authority, the Fulbright Foundation, Sorlandet Hospital, and the National Institutes of Health. Dr. Holme reported no potential financial conflicts of interest; one of his associates reported ties to Exact Sciences, Olympus, and other companies.