Overweight May Skew PSA Prostate Cancer Test

A recent study showed how being overweight can affect your PSA levels, rendering the standard PSA test protocols for diagnosing prostate cancer inaccurate.

The extra blood volume produced in the obese may so dilute levels of a tell-tale protein produced by the prostate gland that the popular PSA test may be SIGNIFICANTLY LESS EFFECTIVE for diagnosing prostate cancer in men carrying extra pounds.

The new findings could eventually also affect the reliability of scores regarding other blood tests for cancer and other diseases in obese people, or at least alter the way those tests are analyzed, investigators say.

The predictive value of the PSA test depends on accurate readings of a protein, (P)rostate (S)pecific (A)ntigen continually produced by the prostate. When the prostate is enlarged - due to cancer or other disorders - the concentration of PSA in the bloodstream can increase, signaling the possible presence of cancer.

Physicians thus commonly regard increased PSA values as a first marker to diagnose prostate cancer, to be followed by other diagnostic tests such as physical exams and a transrectal ultrasound.

Complicating the diagnosis of prostate cancer further, the researchers note, is the fact that both physical exams and imaging studies of the prostate are more difficult in obese men.

Although recent studies have shown that PSA concentrations can be lower than expected in obese men with prostate cancer, the current research was designed to determine which of two dueling hypotheses explained this, notes Alan Partin, M.D., chief of the Department of Urology at Johns Hopkins' Brady Urological Institute.

One idea was based on the possibility that obese men make less PSA because they tend to have less testosterone, the sex hormone that prompts PSA production.

The other theory attributed the phenomenon to the increased amount of blood volume that obese men produce to support their size, which has the effect of thinning out the concentration of PSA.