Obesity and overweight linked to higher prostate cancer mortality

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 December 15, 2007 issue of CANCER, a peer-reviewed journal of  the American Cancer Society. The study has been released online ahead of print publication.

The study, by Matthew R. Smith and colleagues at Massachusetts General Hospital(MGH), 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 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, over 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.

Smith, Director of Genitourinary Medical Oncology at MGH and an Assoociate Professor of Medicine at Harvard Medical School, and his co-investigators reported on 788 patients with locally advanced prostate cancer followed for over 8 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 to  men with 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 to men with normal range BMI. After five years, the prostate cancer mortality rate for men with a normal BMI was less than seven percent  compared to about 13 percent for men with BMI ≥25.

The researchers 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.