Factoring in anatomy and the radiation therapy dose can help doctors predict a prostate cancer patient’s risk of suffering from rectal bleeding as a side effect of therapy, and tailor treatment to prevent the problem, suggests a large study being presented at the 57th Annual Meeting of the American Association of Physicists in Medicine (AAPM).
The rectum receives a high dose of radiation because it pushes up against the prostate, where the cancer is located. As many as one in 10 men who have radiation therapy for prostate cancer suffer from rectal bleeding that can occur several months after the treatment. While not usually life-threatening, rectal bleeding is painful, uncomfortable and inconvenient.
In the study, a collaboration among five institutions, researchers analyzed 1,001 men who received various types of radiation therapy for prostate cancer. While doctors are aware that medium and high doses of radiation to the rectum increase the risk of late rectal bleeding, this the new study found that, the dose being equal, men with shorter rectums were more likely to suffer from rectal bleeding. The probability of bleeding can be predicted using a mathematical formula during treatment planning to minimize the risk.
“By reducing the dose to the edge of the area being irradiated in men with shorter rectums, possibly using better treatment image guidance, we can significantly reduce the risk of late-stage rectal bleeding,” said Joseph Deasy, Ph.D., chair of the Department of Medical Physics at Memorial Sloan-Kettering Cancer Center, New York. “This formula potentially could be put into treatment planning systems that are routinely used.”
Prostate cancer is the most common cancer in men, with 220,000 men diagnosed every year, and is the second leading cause of cancer death in men.
The presenting author of the study is Maria Thor, Ph.D., a post-doctoral fellow at Memorial Sloan-Kettering Cancer Center.