CHICAGO — The first randomized controlled trial to investigate the impact of population-based flexible sigmoidoscopy screening failed to find any significant reductions overall in colorectal cancer incidence or mortality.
But the Norwegian Colorectal Cancer Prevention trial did find that individuals who actually underwent screening were 60% less likely to die from colorectal cancer than were controls who were not screened—a significant reduction.
Dr. Geir Hoff of the Cancer Registry of Norway in Oslo presented 7-year data at the annual Digestive Disease Week. The study took place in Oslo and in Telemark County, Norway. It randomized 55,736 adults aged 55-64 years to an invitation for one-time flexible sigmoidoscopy (13,823) or to no invitation (41,913). Almost 64% of those invited (8,846) did get screened. At screening, 19% had a neoplastic lesion and 5% had a high-risk adenoma or invasive cancer (BMJ 2009;338:b1846).
In the intent-to-screen analysis, cancer risk did not differ between the screening and control groups (135 vs. 132 cases/100,000 person-years). Nor was there a significant difference in the incidence of rectosigmoidal cancers (58 vs. 79 cases/100,000 person-years).
During the follow-up period, 24 participants in the screening group and 99 in the control group died from colorectal cancer. Compared with the control group, total colorectal cancer death was decreased by 27% and rectosigmoidal cancer death by 37% in the screening group—neither was a significant reduction.
The numbers were better for those who actually attended the screening. Total colorectal cancer death was 59% lower in the screened group than in the control group, and rectosigmoidal cancer death was 76% lower—both were significant differences.
The 7-year follow-up period may not have been long enough to allow colon cancers to develop and cause death, Dr. Hoff said.