Johns Hopkins epidemiologists say that prostate cancer patients who gain five or more pounds near the time of their prostate surgery are twice as likely to have a recurrence of their cancer compared with patients whose weight is stable.
"We surveyed men whose cancer was confined to the prostate, and surgery should have cured most of them, yet some cancers recurred. Obesity and weight gain may be factors that tip the scale to recurrence," says Corinne Joshu, Ph.D., M.P.H., postdoctoral fellow at the Johns Hopkins Bloomberg School of Public Health.
Joshu and her colleagues sent questionnaires to 1,337 men with prostate cancer who had undergone surgery to remove their prostate at the Johns Hopkins Hospital. The researchers asked each participant to recall their dietary, lifestyle and medical factors from five years before their surgery through one year after.
Results show that men whose weight increased more than 2.2 kg (or about five pounds of total weight) during the time period had twice the rate of recurrence compared with men whose weight remained the same. On average, the study participants who gained weight reported that they gained about 10 pounds in the five years before surgery and one year postoperation.
"The good news is that being physically active reduced the risk of recurrence associated with obesity," says Elizabeth Platz, Sc.D., M.P.H., associate professor at the Johns Hopkins Bloomberg School of Public Health and co-director of cancer prevention and control at the Johns Hopkins Kimmel Cancer Center.
Platz says that there are a variety of biochemical pathways that may be active in the body depending on daily activity. These pathways also may vary in their impact depending on the stage and type of prostate cancer and timing of obesity and weight gain.
According to the researchers, study size was too small to determine whether weight loss can reverse the recurrence risk. They warn that current prostate cancer patients should heed their physician's advice on weight loss and activity near the time of surgery.
"The overriding message is one that has been repeated many times: adult men should avoid obesity and weight gain," says Platz. "Plus, it will likely have an impact on many aspects of their health."
Joshu and Platz say that several confounding factors may have had an impact in the results, including patients' ability to accurately recall their weight and lifestyle around the time of their surgery. Also, PSA values, an indicator of recurrence, tend to be lower in obese men, so physicians may be slower to detect their recurrent disease. "So, our study may be underestimating the risk of recurrent disease in these men," says Joshu.