(ChemotherapyAdvisor) – Flexible sigmoidoscopy screening resulted in a 26% reduction in overall colorectal cancer mortality and a 21% reduction in incidence of colorectal cancer vs. usual care, according to results of a long-term study in more than 150,000 individuals funded by the National Cancer Institute and published in the New England Journal of Medicine online May 21.
Between 1993 and 2001, members of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial project team randomly assigned 154,900 men and women 55 to 74 years of age to screening with flexible sigmoidoscopy, with repeat screening at 3 or 5 years — the intervention group — or to usual care. Death from colorectal cancer was the primary endpoint.
Baseline flexible sigmoidoscopy was performed in 83.5% of the 77,445 participants randomly assigned to screening; 54% were screened at 3 or 5 years. After a median follow-up of 11.9 years, there were 1,012 cases of colorectal cancer in the intervention group, for an incidence of 11.9 cases per 10,000 person-years. The usual-care group had 1,287 cases, or 15.2 cases per 10,000 person-years, representing a 21% reduction (RR, 0.79; P<0.001).
In the intervention group, there were 479 cases of distal colorectal cancer vs. 669 cases in the usual-care group (RR, 0.71; P<0.001); for proximal colorectal cancer, it was 512 cases vs. 595 cases, respectively (RR, 0.86; P=0.01).
A total of 252 deaths from colorectal cancer occurred in the intervention group, or 2.9 deaths per 10,000 person-years, compared with 341 deaths, or 3.9 per 10,000 person-years, in the usual-care group, representing a 26% reduction (RR, 0.74; P<0.001). For distal colorectal cancer, there were 87 deaths in the intervention group vs. 175 in the usual-care group, for a reduction in mortality of 50% (RR, 0.50; P<0.001). For proximal colorectal cancer, type of screening had no effect on mortality; 143 deaths occurred in the intervention group and 147 in the usual-care group (RR, 0.97; P=0.81).
“Although the trial was not powered to detect the effect of sigmoidoscopic screening on colorectal-cancer mortality and incidence in subgroups, the results are suggestive of a stronger effect among men than among women,” the investigators wrote. “This finding may be due to the fact that women had a lower proportion of screening-detected cancers and a higher proportion of proximal colorectal cancers than men. A significant differential effect between the screening of participants 55 to 64 years of age and those 65 to 74 years of age was not observed.”