(PhysOrg.com) -- Prostate cancer patients who are overweight and have elevated insulin levels are much more likely to die of the cancer than other patients, say researchers at Harvard University and McGill University. Their research is published in the October issue of The Lancet Oncology.
The study was conducted by Dr. Jing Ma, an epidemiologist at the Department of Medicine at Harvard Medical School and the affiliated Channing Laboratory of Brigham and Women’s Hospital, and by Dr. Michael Pollak, director of the Cancer Prevention Unit at McGill University’s Faculty of Medicine and the affiliated Lady Davis Research Institute at the Jewish General Hospital, and their research teams in Boston and Montreal.
While previous studies had suggested a possible link between prostate cancer mortality and obesity, these were not regarded as definitive. The researchers assessed data from 2,546 American men diagnosed with prostate cancer during 24 years of follow-up, and determined that men who were overweight (BMI of 25-29.9) or obese (BMI of 30 or higher) before diagnosis were significantly more likely to die of the disease than men of normal weight.
“It’s a very strong effect,” said Dr. Pollak, McGill’s Alexander Goldfarb Chair in Medical Oncology. “Being overweight and having high insulin levels predicts bad outcome among men who have prostate cancer, and the strength of that relationship is remarkable. In someone with metastatic prostate cancer, the magnitude of the good things that chemotherapy does may be swamped by the bad effects of being overweight. Or, to put it another way, the protective effect of being at your ideal body weight may be more significant than the benefits of chemotherapy.”
In a separate paper published earlier in the year, the researchers discovered insulin receptors on prostate cancer cells. “We have a high level of suspicion that the mediator for this effect is insulin,” Dr. Pollak continued, “At this stage, it’s not as if we can convict insulin in a court of law. However, it is a very serious suspect.”
“We did not do an intervention study; that’s the next step,” he concluded, “but it’s a reasonable assumption that if obese prostate cancer patients lose weight, they may improve their outcome.”
Provided by McGill University
Explore further: Genetic mutation may play key role in risk of lethal prostate cancer in overweight patients