Why is the PSA test so problematic?
Robert Getzenberg: In the 25 years we’ve been using it, the PSA test has changed the face of prostate-cancer treatment. When I started in this field, half of patients had their cancer detected when it had already spread outside the prostate. Today we’re finding cancer earlier, which is reducing mortality. But the test is problematic because PSA itself is not related to cancer. It’s a protease [an enzyme that chops up proteins]. It’s made by the prostate to keep the consistency of the ejaculate right, which is important. PSA may also protect against viral or bacterial invasions. But the prostate gland with cancer doesn’t make any more PSA than the normal prostate. The levels are elevated because the PSA is not going into the ejaculate where it’s supposed to go. Instead, it’s going into the bloodstream, because cancer makes the prostate gland more leaky.
