Prostatic irradiation doesn't lead to any appreciable increase in rectal cancer risk

Men who receive radiation therapy for prostate cancer are not at any appreciable increased risk of developing rectal cancer compared to those not given radiation therapy, according to a new study published in the International Journal of Radiation Oncology-Biology-Physics, the official journal of ASTRO, the American Society for Therapeutic Radiology and Oncology.

This year, 235,000 American men will be diagnosed with prostate cancer. The main ways of dealing with the disease are radiation therapy, surgery and watchful waiting – each of which has its benefits and disadvantages. Researchers have hypothesized that one disadvantage of using radiation to kill the cancer cells in the prostate is that it might also make men more likely to develop cancer in the nearby rectum.

In this study, doctors in Canada evaluated the records of 237,773 men who had prostate cancer. Of them, 33,841 received radiation therapy, 167,607 had their prostate removed surgically and 36,335 received neither treatment. On an initial simple evaluation, doctors found that rectal cancer developed in 243 men who received radiation (0.7 percent), 578 men treated with surgery (0.3 percent), and 227 of the men given neither treatment (0.8 percent). Once doctors had adjusted for the age differences between all the men in the irradiated and non-irradiated groups, they could not find any significant increased risk of rectal cancer in the irradiated men compared to those not given radiation therapy.

“Rectal cancer from other causes is frequent enough in our population to obscure any small incidence of radiation-induced cancer. I hope that the results of this study will help men with prostate cancer and their families put these risks in their proper perspective, and not let their concerns about rectal cancer dissuade them from choosing radiation therapy as a treatment for this disease,” said Wayne S. Kendal, M.D., Ph.D., an Associate Professor in Radiation Oncology at the Ottawa Hospital Regional Cancer Centre in Ontario, Canada.