A commonly used treatment for prostate cancer may increase the risk of colorectal cancer.
Older men with prostate cancer who received treatment that reduced androgen had a 30 to 40 percent higher risk of getting colorectal cancer than men who didn’t have the therapy. The longer they received the treatment, the greater their risk.
Androgen deprivation therapy (ADT) is approved for treatment for men with advanced prostate cancer, but its use is controversial in older men with earlier, low-risk cancer although it is widely used in those men.
The link of ADT to colorectal cancer may help lower-risk men make a decision about therapy for their prostate cancer.
The men received ADT either through a drug that blocked gonadotropin-releasing hormone (GnRH agonist) or by having their testicles removed (orchiectomy).
Increased Risk of Colorectal Cancer
- Men who didn’t receive ADT: 3.7 cases of colorectal cancer per 1,000 person years.
- Men who received GnRH agonist therapy: 4.4 cases per 1,000 person years
- Men who had orchiectomy: 6.3 cases per 1,000 person years.
Colorectal tumors in men who had orchiectomy were more frequently poorly differentiated or undifferentiated.
The study reviewed information in the SEER (Surveillance, Epidemiology, and End Results) and Medicare database and found 107,859 men who were 67 or older at diagnosis, diagnosed from 1993 through 2002, and had follow-up information through 2004. About half (55,901 ) had ADT during that time — most (50,097 ) treated with GnRH blockers, but 5,804 had orchiectomy.
Since radiation therapy for prostate cancer increases risk for rectal cancer, the research team looked at men who got radiation treatment and found that the increased risk with ADT was unchanged.
Silke Gillessen, MD, and the team at the University of Michigan in Ann Arbor, wrote in an early online edition of the Journal of the National Cancer Institute,
Long-term androgen deprivation therapy for prostate cancer is associated with an increased risk of colorectal cancer.
In an accompanying editorial in JNCI, Jennifer H. Lin and Edward Giovannucci discuss the impact of the study on our understanding of how sex hormones affect the development of colorectal cancer. They point out that decisions about ADT need to be made in light of potential impact on colorectal cancer and that men who are being treated with androgen deprivation therapy need careful screening for colorectal cancer as well as lifestyle practices like physical activity that reduce its risk.
Although some subgroups of prostate cancer patients will benefit overall from androgen deprivation therapies, the medical side effects and effects on quality of life are important considerations. The findings of Gillessen et al. suggest that an elevated risk of colorectal cancer may be an additional consideration to weigh in the risk vs benefit profile. Their findings also reinforce the need for routine screening for colorectal cancer and the adoption of lifestyle practices such as physical activity that may help to counter some of the drawbacks of anti-androgen therapies.
A study reported two years ago in the Journal of the American Medical Association found no difference in overall survival between men with locally limited prostate cancer who got primary androgen deprivation therapy (PADT) did no better than men who had no treatment at all.
Grace L. Lu-Yao and her team wrote,
In conclusion, our analyses suggest that PADT is not associated with improved survival among the majority of elderly men with T1-T2 prostate cancer. The significant adverse effects and costs associated with PADT, along with our finding of a lack of overall survival benefit, suggest that clinicians should carefully consider the rationale for initiating PADT in elderly patients with T1-T2 prostate cancer.
SOURCES: Gillessen et al, Journal of the National Cancer Institute, Advance Access, November 10, 2010.