A history of type 2 diabetes is not associated with more aggressive prostate cancer, but it does predict worse long-term survival from the disease, according to a study presented on Sunday at the annual meeting of the American Society for Therapeutic Radiation and Oncology (ASTRO), being held this week in Denver.
The Fox Chase Cancer Center, Philadelphia, study included 1,512 men with localized prostate cancer who received 3D conformal radiation therapy between April 1989 and October 2001. Of these, 206 had type 2 diabetes that was treated with diet, exercise or medications other than insulin.
There were no differences in initial prostate-specific antigen (PSA) scores or cancer stage between the diabetics and nondiabetics, lead investigator Dr. Khahn H. Nguyen announced. Five years after radiation therapy, PSA scores reflected a treatment failure rate of 27.2 percent in the nondiabetics and 23.8 percent in diabetics. Distant spread of the cancer developed in 7 percent of nondiabetics and 4.9 percent of diabetics.
Nguyen reported that “although men with type 2 diabetes did not have significantly different treatment outcomes, having the disease had a detrimental effect on overall outcome.” Nondiabetics had an overall death rate of 19.1 percent compared with 22.8 percent in type 2 diabetics. The difference was statistically significant even after consideration of other pretreatment risk factors.
“Diabetes is associated with other risk factors for death, such as cardiovascular disease and obesity, where the body gains too much weight to respond normally to insulin,” Nguyen said in an interview with Reuters Health. “The numbers in this study were too small to see if insulin was a factor,” but the findings suggest that insulin is a growth factor that may stimulate prostate cancer cells.
“Oncologists should pay attention to other factors, such as diabetes, smoking, exercise and diet in patients with prostate cancer,” Nguyen noted. “They should encourage lifestyle changes and use a multidisciplinary approach in managing the patient with prostate cancer and diabetes.”
The Fox Chase investigator stressed that a large, multicenter trial is still needed to assess the effect of diabetes treatment on prostate cancer outcomes.