Men who are overweight or obese when they are diagnosed with prostate cancer are more likely to die from the disease than men who are of healthy weight, according to a Kaiser Permanente study published in the journal Obesity Research & Clinical Practice. In patients with more aggressive forms of prostate cancer, the researchers also found an even stronger correlation between obesity and mortality.

This study included 751 Kaiser Permanente patients with prostate cancer who underwent radical prostatectomy, an operation that includes removal of the prostate and surrounding tissue. The researchers explored the association between the patients' body mass index and prostate cancer mortality, adjusted for tumor aggressiveness and other characteristics.

The researchers found men who died from prostate cancer were 50 percent more likely to be overweight or obese at diagnosis compared to men who did not die from the disease. Men with high Gleason scores, a rating of the aggressiveness of prostate cancer cells, had the highest association between BMI and death, specifically men with Gleason scores of 8 or higher. The Gleason score ranges from 2 to 10, with the highest number representing the greatest likelihood of tumor cells spreading.

"We found among patients undergoing surgical treatment for prostate cancer, weight at time of diagnosis is more strongly correlated with prostate cancer survival than many other factors researchers have studied in the past, including some prostate cancer treatments," said lead author Reina Haque, PhD, a researcher at Kaiser Permanente Southern California's Department of Research & Evaluation in Pasadena, Calif. "Moving forward, we are hoping future studies will examine the effect of weight loss and other lifestyle modifications on prostate cancer mortality."

Additional studies are needed to determine which lifestyle modifications, such as diet or exercise, could prolong a prostate cancer patient's life. Further investigation also is needed to determine if the findings of this study, which looked at men who had prostate cancer surgery, apply to men who received other treatments such as radiation or hormone therapy.

Although the connection between men's weight at prostate cancer diagnosis and likelihood of survival has been examined, many previous studies were limited by self-reported body weight data or it was unclear when the BMI data were obtained. So the link between obesity and prostate cancer mortality remains controversial. However, the methodology of this study was different because the researchers used BMI collected from medical records, instead of self-reported data. The researchers identified men who died of prostate cancer and compared their BMI at time of diagnosis to controls to determine if body weight is related prostate cancer death. The biological relationship between obesity and prostate cancer prognosis is still not understood, and is an active area of research.