Two new studies show obese men with prostate cancer are at a higher risk of developing more aggressive tumors and of experiencing cancer recurrence than men of normal weight.
The first study conducted by researchers at the Naval Medical Center in San Diego sampled nearly 3,200 prostate cancer patients. In this group, 19 percent of the patients were considered obese -- defined as having a body mass index higher than 30.
Researchers found a correlation between obesity and a higher Gleason score, the value used to classify the aggressiveness of prostate tumors. They also found obese men tended to have a higher cancer recurrence rate.
The second study was conducted by researchers at Johns Hopkins University School of Medicine on nearly 1,100 prostate cancer patients, 22 percent of who were obese. In this study, obesity was defined as a body mass index higher than 35. As in the first study, researchers concluded that obese men also were more like to have a higher Gleason score. Another similar conclusion was that in both studies black men were more likely to be obese.
Stephen J. Freedland, M.D., co-author of the study, says, "We suspect that worse outcomes among African-American men with prostate cancer are related to obesity rather than race."
Researchers for both studies suggest that proteins and hormones stored in body fat -- such as leptin and insulin-like growth factor 1 -- may encourage prostate tumor growth in obese men. Also, obese men usually have lower testosterone levels and higher estrogen levels, which may promote cancer growth. In addition, diets high in fat may promote tumor growth.
Medical peers agree with the conclusions of the studies and encourage further investigation. Alfred I. Neugut, M.D., Ph. D., of Columbia University, says, "The number of prostate cancer survivors is steadily increasing, and it will be important to investigate if weight loss and other lifestyle changes can improve prognosis in those already diagnosed with prostate cancer."