Early detection of colorectal cancer

The largest study to date on the early detection of colorectal cancer offers benchmark data for what could be expected from large-scale use of flexible sigmoidoscopy as a screening tool for colorectal cancer.

The report, published in the July 6 issue of the Journal of the National Cancer Institute (JNCI), is part of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, a randomized, community-based longitudinal study evaluating the effectiveness of cancer screening tests on site-specific mortality.

“In our opinion, we now have published important and valuable baseline data on the use of flexible sigmoidoscopy within a large and randomized group of participants,” said Joel Weissfeld, M.D., M.P.H, lead author of the study and associate professor of epidemiology, University of Pittsburgh Graduate School of Public Health. “The findings reveal trends and patterns by gender and age that one may expect to see in a flexible sigmoidoscopy intervention targeting the general U.S. population,” added Dr. Weissfeld, who also is co-leader of the cancer epidemiology, prevention and control program at the University of Pittsburgh Cancer Institute.

During flexible sigmoidoscopy (FSG), a doctor uses a lighted scope to examine the inside of the large intestine from the rectum through the descending colon, where most colon polyps develop.

The study enrolled 154,942 men and women 55 to 74 years of age who had no prior history of prostate, lung, colorectal or ovarian cancers from November 1993 to July 2001. Study participants were randomly assigned to either a control group that did not receive FSG or to an intervention group that received FSG. Of those assigned to the intervention group, 83.5 percent (64,658) agreed to undergo an initial FSG examination. Among the individuals who underwent screening, 23.4 percent (15,150) had at least one polyp or mass and 74.2 percent of these individuals received follow-up lower endoscopic procedures. Findings also indicated that women were more likely to decline FSG than men, 19.2 percent and 13.8 percent respectively, and that non-acceptance of FSG increased with age among women, but not among men. The rate of cancer detected was 2.9 per 1,000 individuals screened.

“These data are important because they create a U.S. benchmark to which other studies can be compared,” said Robert E. Schoen, M.D., M.P.H., study co-author and associate professor of medicine and epidemiology, University of Pittsburgh School of Medicine. “Of note is that a high percentage of study participants were willing to undergo flexible sigmoidoscopy, perhaps reflecting a growing acceptance of screening for colorectal cancer.”

Colorectal cancer is a worldwide public health problem. In the United States, colorectal cancer accounts for 11 percent of all cancers, with 145,290 new cases and 56,290 deaths expected in 2005. For patients with advanced disease, five-year survival rates are 10 to 20 percent. When colorectal cancer is diagnosed at an early, localized stage, the five-year survival rate is 90 percent.

Co-authors of the study include Robert S. Bresalier, M.D., M.D. Anderson Cancer Center; Timothy Church, Ph.D., University of Minnesota; Susan Yurgalevitch, Westat Inc, Rockville, Md.; Joseph H. Austin, Information Management Services, Rockville, Md.; Paul F. Pinsky, Ph.D., Philip C. Prorok, Ph.D., and John K. Gohagan, Ph.D., National Cancer Institute.