Prostate cancer survivors take note: Carrying extra pounds may increase the chances of the disease returning after treatment, a new study finds.
And the greater the excess body weight, the greater the risk.
"If a man is diagnosed with prostate cancer that appears to be at a curable stage, excess body weight is associated with having a larger and more aggressive tumor that is more likely to recur after surgery," said researcher Vincent Freeman, an associate professor of epidemiology and biostatistics at the University of Illinois in Chicago.
"Recurrence" is generally defined as the return of cancer after treatment has succeeded for a period of time, although there is no set time length specified.
In the new study, presented at the American Association for Cancer Research annual meeting in Chicago this week, Freeman and his colleagues examined the body mass index -- a measurement of weight relative to height -- of 119 men in the Chicago area who were slated to undergo surgery for clinically localized prostate cancer. The researchers also used a common risk assessment system that takes into account factors like blood PSA levels and biopsy results in order to predict the likelihood that the men's cancer would return.
They found that men who had an average BMI of 37 were almost eight times more likely to have prostate cancer with a moderate-to-high risk of returning after treatment versus men with a lower BMI. (A BMI of 30 and higher is considered obese.)
Men with lower BMIs, but still classified as overweight, were between 3 and 6 percent more likely to have prostate cancer with a substantial risk of returning.
"The literature overall is moving toward a concept that BMI is important in terms of aggressiveness of the disease at diagnosis and now this suggests it impacts recurrence," said Dr. Willie Underwood, an associate professor in the Department of Urology at the Roswell Park Cancer Institute.
Indeed, prior studies looked at the possible link between prostate cancer and body mass, including a 2007 paper from National Cancer Institute that found obese men had a higher risk of dying from the disease.
"It fits into the concept that the healthier you are, the healthier you are, the healthier you are," Underwood continued, adding that future studies would need to confirm the findings and also unpack questions about whether or not carrying excess weight for just a short period of time increased risk.
In an e-mail to The Huffington Post, Freeman offered several explanations for the connection between BMI and recurrence suggested in the new study.
"As we get older, excess body weight is usually in the form of excess body fat," he said, explaining that the research focused only on men whose prostate cancer was in an early, potentially curable stage. "Body fat produces substances that can promote the growth of cancer cells directly or indirectly by causing other metabolic disturbances linked to cancer."
Dr. Reza Ghavamian, a professor of clinical urology at the Montefiore Medical Center, said that the exact role that weight plays with regards to prostate cancer is not yet fully understood, but the current study is notable in that it is among the first to point to the role weight can play not just pre-diagnosis, but afterwards.
"What's unique here is that they're talking about excess body weight not with prostate cancer development, but as a risk factor for prostate cancer recurrence," said Ghavamian, who cautioned, however, that the new study is relatively small and did not include many patients.
"It suggests that the just the removal of the cancer isn't enough," he continued. "You may have to conform to a certain amount of lifestyle change."