Prostate Radiation Linked to Rectal Cancer

Men who receive radiation treatment for prostate cancer are more likely to develop rectal cancer, a new study suggests.

Researchers found that men with prostate cancer who were treated with radiation had a 70 percent higher risk of developing rectal cancer than those who were treated with surgery only.

"Men who have had prostate radiation should be aggressively monitored for rectal cancer starting five years after treatment," says researcher Nancy Baxter, MD, PhD, of the University of Minnesota Cancer Center, in a news release. "This is the first time rectal cancer risk associated with prostate radiation has been quantified, and these findings may also have implications for patients treated with radiation for other pelvic cancers."

Prostate cancer is the most commonly diagnosed cancer in the U.S. with about 230,000 men diagnosed with the disease each year. Although prostate cancer is highly treatable when caught in the early stages, researchers say men who survive prostate cancer may face higher risks of other types of cancer due to the effects of their treatment.

About 17 percent of men with prostate cancer are treated with radiation, usually because they choose radiation over surgery, are older, or have other medical problems.

Prostate Cancer Treatment May Raise Other Risks

In the study, which appears in the April issue of Gastroenterology, researchers looked at more than 85,000 men treated for prostate cancer from 1973 to 1994.

More than 30,000 of the men received radiation treatment for prostate cancer and about 55,000 had surgery only.

The results showed that radiation treatment was linked to a higher risk of cancer in areas that were irradiated, such as the rectum, but not in the remainder of the colon. The risk of developing rectal cancer among men who received radiation was 70 percent higher than those who underwent surgery alone.

Researchers say that increase in risk is roughly equivalent to the colorectal cancer risk associated with having a family history of the disease.

Improvements With Current Technology

However, researchers say current technology allows for more targeted radiation treatment to the affected area than was available up to 1995. Even so, researchers say some portions of the rectum may still receive a high dose of radiation, which raises the risk of rectal cancer.

In an editorial that accompanies the study, William M. Grady of the Fred Hutchinson Cancer Research Center in Seattle and Ken Russell of the University of Washington Medical School say that the results highlight the need to monitor the long-term health of prostate cancer survivors.

“In light of the increasing number of men surviving prostate cancer, these findings have substantial implications not only regarding our understanding of radiation-induced cancers but also for our management of men who have undergone prostate irradiation,” write the editorialists.

“As more men are successfully treated for their prostate cancer, the prevention of long-term complications from prostate cancer treatment can be predicted to become a major medical issue.”

By Jennifer Warner, reviewed by Michael W. Smith, MD

SOURCES: Baxter, N. Gastroenterology, April 2005; vol 128: pp 819-824. News release, American Gastroenterological Association.