Men who are overweight or obese when diagnosed with prostate cancer are at greater risk of death after treatment, according to a new study in the Dec. 15 issue of Cancer, a peer-reviewed journal of the American Cancer Society. The study, by Jason Efstathiou from Harvard-affiliated Massachusetts General Hospital and colleagues, found that a greater body mass index (BMI) at the time of cancer diagnosis was an independent risk factor for prostate cancer-related death. Overweight and obese men (men with BMI > 25 kg/m2) at the time of diagnosis were nearly twice as likely to die from locally advanced prostate cancer as patients who had a normal BMI at diagnosis.
In 2007, more than 218,000 American men are expected to be diagnosed with prostate cancer and over 27,000 will die from the disease. While obesity has been identified as a risk factor for more clinically aggressive prostate cancer, the impact of obesity on survival following treatment is less understood. These treatments may include the complete surgical removal of the prostate, external beam radiation, and hormonal therapy.
Efstathiou and co-investigators reported on 788 patients with locally advanced prostate cancer followed for over eight years to examine any independent relationship between BMI and prostate cancer-specific mortality. The study is the first to use data from a large randomized prospective treatment study with long-term follow-up to investigate this relationship.
The authors found that being overweight or obese at the time of diagnosis was a unique, independent risk factor for death from prostate cancer. Compared with men having normal BMI (BMI<25), men with BMI between 25 and 30 were more than 1.5 times more likely to die from their cancer. Similarly, men with BMI > 30 were 1.6 times more likely to die from their disease compared with men having normal-range BMI. After five years, the prostate cancer mortality rate for men with a normal BMI was less than 7 percent compared with about 13 percent for men with BMI > 25.
Efstathiou and his co-authors conclude that their data support population-based studies that report similar associations between obesity and disease-related mortality. “Further studies are warranted to evaluate the mechanisms for this increased cancer-specific mortality among overweight and obese men and to assess the impact of BMI on survival following other management strategies and in clinically localized disease. Whether weight loss after prostate cancer diagnosis alters disease course remains to be determined,” conclude the authors.