CHICAGO—Higher body mass index (BMI) is associated with higher plasma volume, which may be related to lower prostate-specific antigen (PSA) levels among obese men, according to a study in the November 21 issue of JAMA.
Recent evidence has suggested that prostate cancer screening may be adversely affected by increased BMI. The ability to accurately detect prostate cancer can be compromised by any factor that decreases PSA concentration in the circulation, according to background information in the article. Several studies have found that obese men have lower PSA concentrations than non-obese men. "However, men with higher BMIs also have larger plasma volumes, which could decrease serum concentrations of soluble tumor markers—a phenomenon known as hemodilution," the authors write.
Lionel L. Bañez, M.D., of Duke University Medical Center, Durham, N.C., and colleagues conducted a study to determine the association between hemodilution and PSA concentration in obese men with prostate cancer. The study consisted of men who underwent radical prostatectomy for prostate cancer from 1988 to 2006 and who were included in the databases of the Shared Equal Access regional cancer hospital (n = 1,373), Duke Prostate Center (n = 1,974), and Johns Hopkins Hospital (n = 10,287).
The researchers found that higher BMI was significantly associated with greater plasma volume in all study populations. Men with a BMI of 35 or greater had 21 percent to 23 percent larger plasma volumes relative to normal-weight men. After adjusting for multiple clinico pathologic al variables, higher BMI was associated with lower pre-operative PSA concentrations in the groups. Men with a BMI of 35 or greater had 11 percent to 21 percent lower PSA concentrations relative to normal-weight men.
"In 3 distinct prostate cancer cohorts, all treated by radical prostatectomy, hemodilution from increased plasma volume may be responsible for the observed decreased PSA concentration in men with higher BMI. This association needs to be confirmed prospectively in screened populations that include men without prostate cancer," the authors conclude.
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