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 at the annual meeting of the American Society for Therapeutic Radiation and Oncology (ASTRO), being held this week in Denver, CO. The Fox Chase Cancer Center, Philadelphia, study included 1,512 men with localised prostate cancer who received 3D conformal radiation therapy (3D-CRT) between April 1989 and October 2001. Of these, 206 had Type 2 diabetes mellitus managed with diet, exercise or medications other than insulin.

There were no differences in initial prostate-specific antigen (PSA) score, Gleason score or T stage between the diabetics and nondiabetics, lead investigator Dr Khahn H. Nguyen announced. Five years after radiation therapy, PSA scores reflected a biochemical failure rate of 27.2% in the nondiabetics and 23.8% in diabetics. Distant metastases developed in 7% of nondiabetics and 4.9% of diabetics.

Dr 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 mortality rate of 19.1% compared with 22.8% in Yype 2 diabetics. The difference was statistically significant even after adjusting for other pretreatment 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," Dr Nguyen said in an interview with Reuters Health. "The numbers in this study were too small to see if insulin was a factor," but preclinical data suggest that insulin is a growth factor that may stimulate prostate cancer cell proliferation.

"Oncologists should pay attention to other factors, such as diabetes, smoking, exercise and diet in patients with prostate cancer," Dr Nguyen noted. "They should encourage lifestyle changes and use a multidisciplinary approach in managing the patient with prostate cancer and diabetes."

"This is a retrospective study," the Fox Chase investigator cautioned. "We need to conduct a large, multicenter randomized trial to assess the management of diabetes on prostate cancer outcome."