HOUSTON - How heavy a man is at the time he is diagnosed with prostate cancer, as well as his history of weight gain, appear to play significant roles in how aggressive his cancer may become, say researchers at The University of Texas M. D. Anderson Cancer Center.
While a link between weight and initial development of prostate cancer already has been made, this report, published in the Oct. 1 issue of Clinical Cancer Research, is the first to associate a man's body mass at different ages and adult weight gain with the risk of progression after his prostate cancer has been surgically treated.
"These findings support the view that the development of aggressive forms of prostate cancer may be influenced by environmental effects that occur early in life," says the study's lead researcher Sara Strom, Ph.D., an associate professor in the Department of Epidemiology.
Given further validation of the results, Strom suggests a man's history of body weight should be a factor oncologists consider when designing a treatment plan for patients newly diagnosed with prostate cancer.
The data also suggest that interventions such as diet and exercise could be a way to reduce the risk of prostate cancer progression, Strom says.
Researchers based their findings on outcomes from 526 M. D. Anderson prostate cancer patients treated by surgery (prostatectomy). They followed the progress of the patients for an average of 4 1/2 years, checking whether the men entered "biochemical failure" or a rising prostate specific antigen (PSA) level, which can indicate the cancer is advancing.
"After surgery, a patient's PSA should go back to being undetectable, but if it begins to rise, that is an indicator of progression," Strom says. "Thirty percent of men who have biochemical failure will develop a life-threatening cancer metastasis, and so PSA is the only marker we have as yet to predict whose cancer will spread."
Within the group, 18 percent of the patients went into biochemical failure. Researchers then correlated an individual's risk of experiencing that failure with his weight history. They found that:
- Men who were obese (body mass index [BMI] of 30 or more) when they were diagnosed with prostate cancer were more likely to experience biochemical failure than those who were not obese;
- Patients who were obese at age 40 had an even greater rate of biochemical failure; and
- Men who gained weight at the greatest rate between age 25 and the time of their diagnosis experienced disease progression significantly sooner (an average of 17 months) than those men who gained weight more slowly (an average of 39 months).
Strom says that it is currently unclear how excess obesity contributes to prostate cancer progression, although leading theories suggest it could be linked to changes in a number of different hormones (such as androgen and growth factors) and/or lifestyle behaviors (such as poor diet and inadequate physical activity). But she adds that "understanding the mechanisms by which weight gain contributes to prostate cancer progression will lead to rationally designed preventive strategies."
The study was funded by the National Cancer Institute. Co-authors include principal investigator Patricia Troncoso, M.D., Xuemei Wang, Curtis Pettaway, M.D., Christopher Logothetis, M.D., Yuko Yamamura, Kim-Anh Do, Ph.D., and Richard Babaian, M.D.
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