Long-term androgen deprivation therapy for the treatment of prostate cancer may increase the risk of colorectal cancer. These findings were recently published in the Journal of the National Cancer Institute.
The prostate is a male sex gland responsible for producing fluid that forms semen. It is located below the bladder, in front of the rectum, and surrounds the urethra. Prostate cancer occurs when the cells in the prostate gland grow out of control.
Prostate cancer is a hormonally sensitive disease that can often be controlled for long periods with androgen deprivation therapy (ADT). Hormonal therapy for prostate cancer, also known as androgen deprivation therapy, is designed to prevent testosterone from stimulating the growth of hormone-dependent types of prostate cancer. Androgen deprivation can be achieved through the use of medications such as gonadotropin-releasing hormone (GnRH) agonists or by surgically removing the testicles (bilateral orchiectomy).
In May of 2010, the US Food and Drug Administration (FDA) reported that patients undergoing treatment with GnRH agonists were at a “small increased risk for diabetes, heart attack, stroke, and sudden death.” Recently, the FDA requested that new warnings be added to the labels of GnRH agonists to inform patients and healthcare professionals of the potential risks of heart disease and diabetes.
The current study evaluated the relationship between ADT and risk of colorectal cancer. Researchers evaluated data from 107,859 prostate cancer patients diagnosed from 1993-2002. Information about prostate cancer and any subsequent colorectal cancer was collected from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database.
The researchers concluded that “long-term androgen deprivation therapy for prostate cancer is associated with an increased risk of colorectal cancer.” Prostate cancer patients undergoing androgen deprivation therapy may wish to speak with their physician about the risks and benefits of treatment, as well as recommendations regarding colorectal cancer screening and prevention.
It should be noted that this study included only Medicare enrollees; it’s not clear whether the results also apply to younger men with prostate cancer. Furthermore, although the researchers attempted to account for differences between the study groups, it’s possible that something other than the ADT explains the higher risk of colorectal cancer among men treated with ADT.
 FDA News Release. FDA: Include warnings on risk for class of prostate cancer drugs. October 20, 2010.