PSA changes predict prostate cancer outcome

Watching changes in men’s PSA blood tests may be the best way of predicting which men have life-threatening prostate cancer, U.S. researchers said on Tuesday.

The study, published in the Journal of the National Cancer Institute, strengthens the argument that men should have their prostate specific antigen (PSA) levels tested when they are young, so doctors have a point of reference, or “baseline,” for studying future changes.

“We have found that the rate at which a man’s PSA rises may be more important than any absolute level for identifying men who will develop life-threatening cancer while their disease is still curable,” said Dr. H. Ballentine Carter of the Johns Hopkins School of Medicine in Baltimore.

“In addition, PSA velocity could be a useful method for identifying those men with a prostate cancer that could be safely monitored—an approach termed ‘active surveillance.’”

The PSA test is often used to screen for prostate cancer. PSA is a protein made only by prostate cells. PSA levels rise as tumor cells multiply.

But PSA can also rise as a man’s prostate gland grows with age and in prostate cancer infections, and some men with cancer have low PSA levels. So the test is considered imperfect.

Men are advised to get a digital rectal exam, in which the doctor checks the size of the prostate, which is normally about the size of a walnut and located internally between the testes and the anus. Cancer can only be diagnosed with a biopsy, a tiny sample of prostate tissue.

Prostate cancer is common. This year, 234,460 men in the United States will be diagnosed with prostate cancer, according to the American Cancer Society. But only about 30,000 will die of it, because the tumors can be very slow-growing.

Carter and colleagues assessed the PSA velocity of 104 men diagnosed with prostate cancer who had not died from the disease, 20 men who died of prostate cancer, and 856 men without prostate cancer. The researchers looked at blood samples from the men dating back as far as 1958.

They found that a patient’s PSA velocity 10 to 15 years before his cancer diagnosis was associated with survival 25 years later. Patients with a lower PSA velocity had a 92 percent survival rate, while patients with a higher PSA velocity had a 54 percent survival rate.

“We would recommend that men at around age 40, not 50, have their PSA checked to develop a baseline against which to compare future changes (velocity), since even a slight rise in PSA may indicate a potential for cancer down the road,” Carter said in a statement.

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