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Linking body size and prostate cancer risks

Vincent Freeman photo.

For men with prostate cancer whose tumors appear to be limited to the prostate gland, surgery usually results in a clean bill of health from this curable disease. But among men who are obese, their prostate cancers are more likely to recur after surgery. SPH’s Vincent Freeman, MD, (MPH ’94), associate professor of epidemiology, is studying what exactly might cause this phenomenon.

“We have population-based studies that tell us as body mass index (BMI) increases, your risk of dying of prostate cancer increases,” Freeman said. “What we want to know is whether this might be due to body fat burden, or perhaps because people with a higher BMI might be eating more foods potentially causally related to the prognosis of the cancer.”

With funding from the National Cancer Institute, Freeman’s cohort study identified a strong association between body fatness and risk of recurrent prostate cancer after surgery. This association was present even in men who were not obese.

Freeman says body fat is known to produce substances that have been implicated in the development and progression of cancers. One hypothesis to explain the results of the cohort study suggests elevated body fat, as reflected to an extent by elevated BMI scores, increases the risk of earlier metastases of the tumor in the prostate in ways that evade detection when the cancer is being staged. As a result, some prostate cancer cells remain in the body after surgery. The substances created by body fat may cause tumors to metastasize earlier rather than later in the course of the disease.

Freeman says a confirmation of this hypothesis would allow for targeted screenings for men with elevated BMI scores, to identify particular proteins in the bloodstream that are associated with earlier metastases. Likewise, he envisions potential interventions and lifestyle modifications toward
body composition. At the same time, Freeman cautions that any research or interventions in this vein must take a person-centric approach.

“It’s important to remember that the association between body fat and cancer recurrence after surgery was observed in non-obese men,” Freeman said. “Therefore, preventing prostate cancer recurrence after surgery may ultimately involve addressing body composition.”