SAN DIEGO – The incidence of colorectal cancer among men and women who underwent flexible sigmoidoscopy, with a repeat screening every 3 or 5 years, was reduced by 21%, compared with those who received usual care, according to the findings of a large, randomized controlled trial.
In addition, results from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) showed that study participants in the flexible sigmoidoscopy group had a 26% reduction in overall colorectal cancer mortality and a 50% reduction in mortality related to distal colorectal cancer, compared with the usual-care group. In about 22% of cases, colonoscopy was performed as a direct effect of screening with flexible sigmoidoscopy.
Dr. Robert E. Schoen of the division of gastroenterology, hepatology, and nutrition at the University of Pittsburgh Medical Center and his associates randomly assigned 154,900 men and women aged 55-74 years to either screening with a baseline flexible sigmoidoscopy, with a repeat screening every 3 or 5 years, or to usual care, which was defined as "whatever might have been recommended by the patient’s physician," he said.
"The rate of routine colonoscopy after the screening phase was 47.7% in the intervention group and 48.0% in the usual-care group, according to the study.
The investigators followed the study participants for a median of 11.9 years and collected medical records related to follow-up, a diagnosis of cancer, and cancer complications. The primary outcome was death from colorectal cancer, while incidence of the disease was listed as a secondary outcome (N. Engl. J. Med. 2012 May 21 [doi:10.1056/NEJMoa1114635]).
Of the 154,900 study participants, 77,445 were assigned to the flexible sigmoidoscopy group and 77,455 to the usual-care group. The groups were evenly split by gender, more than half (64%) ranged in age from 55-64 years, 86% were white (non-Hispanic), and 34% were college graduates.
Dr. Robert E. Schoen
During follow-up, the incidence of colorectal cancer was 11.9 cases/10,000 person-years in the intervention group, compared with 15.2 cases/10,000 person-years in the usual care group, which translated into a statistically significant reduction of 21% (P less than .001).
The researchers also reported that there were 2.9 deaths from colorectal cancer/10,000 person-years in the intervention group, compared with 3.9/10,000 person-years in the usual care group, which translated into a statistically significant reduction of 26% (P less than .001). Mortality from distal disease was reduced by 50% in the intervention group, compared with the usual care group (P less than .001), but mortality from proximal disease remained unaffected (P = .81).
"As compared with the distal colon, the proximal colon poses a more difficult challenge for colorectal cancer control because of limitations in bowel preparation, a greater prevalence of advanced serrated adenomas, which are harder to detect than conventional adenomas, and biologic differences, including a greater incidence of BRAF mutation, microsatellite instability, and CpG island methylator phenotype (CIMP)," the researchers wrote.
"Although our protocol was associated with a reduction in the incidence of proximal colorectal cancer, presumably because of the detection and removal of precursor adenomas that would otherwise have progressed to cancer, it apparently did not succeed in identifying and successfully removing a proportionally greater number of precursor lesions destined to develop into fatal colorectal cancers."
At the meeting, Dr. Schoen told this news organization that clinicians "have to become better at detecting subtle polyps in the right [proximal] colon. The hope is that if we get better with colonoscopy we will be able to find not just the polyps that lead to cancer, but also the polyps that lead to fatal cancer."
Dr. Schoen disclosed that he has received stock options from Onconome. The study was funded by the National Cancer Institute.