Weight, not diabetes, related to prostate-cancer mortality

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While diabetic men with prostate cancer are no more likely to die from their cancer than are men who are not diabetic, increased body weight does increase the likelihood of prostate cancer-related death, according to results from a Radiation Therapy Oncology Group (RTOG) trial presented at the 2008 American Society of Clinical Oncology (ASCO) meeting in Chicago this week.

The researchers showed that men with diabetes have a lower risk of developing prostate cancer. However, the RTOG authors wrote that little was known about the role of diabetes in those men, who develop prostate cancer. 

“Based on the results of our investigation, we now know that the real risk factor is not diabetes, but rather obesity,” said lead author Matthew Smith, MD, PhD, of the department of medicine at Harvard Medical School in Boston. “We controlled for age, race, tumor stage, Gleason score, PSA, diabetes, weight and treatment assignment and found that weight, not diabetes, was the better predictor of prostate cancer mortality.”

Using the data from a large randomized trial (RTOG 9202) of 1,554 men treated with radiation therapy and short-term versus long-term adjuvant hormone therapy for locally advanced prostate cancer, the RTOG investigators examined the relationship between diabetes and cancer-related death, non-cancer-related death and overall mortality.

The researchers found that diabetes was significantly associated with deaths from all causes and deaths from non-prostate cancer-related causes, but not prostate cancer deaths. 

In contrast, weight was associated with a higher incidence of prostate cancer deaths but not deaths from all causes or non-prostate cancer deaths, according to the RTOG investigators.

RTOG, an NCI-funded national clinical trials group, is a clinical research component of the American College of Radiology (ACR).