The study, which is part of the National Cancer Institute’s Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, provides the strongest evidence to date that screening reduces colorectal cancer deaths and prevents people from getting the disease, endorsing the importance of colorectal cancer screening for everyone.
“Colorectal cancer screening is effective because we’re not just searching for cancer. We’re identifying the precursors of cancer, colorectal polyps, and removing them. By doing so we are preventing cancer from developing,” said Robert E. Schoen, M.D., M.P.H., professor of medicine and epidemiology at the University of Pittsburgh, and lead author of the study. “It’s the ultimate public health success story.”
Colorectal cancer is the second-leading cause of cancer death in the U.S., with more than 50,000 people dying from the disease each year. Progress has been made in reducing incidence and death rates from the disease, thanks in part to screening, but there is potential for an even greater reduction.
For the study, which began in 1993, 154,900 men and women from the ages of 55 to 74 were randomly assigned to screening with flexible sigmoidoscopy with a repeat screening at three or five years, or to “usual care,” which means whatever screening they might receive in routine medical care with their physician. Over 86 percent of the subjects underwent a screening exam. Most subjects with abnormal sigmoidoscopy screening results then had a full colonoscopy. Overall, the screening resulted in a 21 percent reduction in cancer incidence and 26 percent decline in colorectal cancer deaths. There was a 50 percent reduction in death due to distal colon cancer, the portion of the colon that can be directly examined by the flexible sigmoidoscopy exam.
“There is still room for improvement. Our biggest obstacle is the underutilization of screening,” said Dr. Schoen. “Right now, 40 percent of the U.S. population is not getting screened, and we know screening works. We need to encourage everyone to undergo screening to save themselves from this potentially deadly disease, and to reduce the unnecessary public health burden and expense of colorectal cancer.”
This study was funded by the National Institutes of Health’s National Cancer Institute; grant number NCT00002540.