PSA test poor predictor of prostate cancer outcome

NEW YORK (Reuters Health) - The results of a recent study suggest that the initial prostate-specific antigen (PSA) test and rate of change in PSA levels are poor predictors of aggressive prostate cancer among patients whose cancer has not spread and opt for a "watchful waiting" approach.

"Rates of long-term survival among patients with untreated localized prostate cancer are high," Dr. Katja Fall, of the Karolinska Institute, Stockholm, and colleagues write in the Journal of National Cancer Institute. "To avoid unnecessary treatment, tools are needed to identify the small proportion of patients who are destined to develop lethal prostate cancer."

To evaluate the accuracy of early changes in PSA levels in predicting prostate cancer outcome, the researchers assessed PSA levels for 267 men with localized prostate cancer who were diagnosed between 1989 and 1999 and were followed by watchful waiting, in which they were closely monitored by their physician, but received no treatment.

The patients were followed for an average of 8.5 years. During that time, 34 patients (13 percent) died from prostate cancer and 18 (7 percent) experienced spread of their disease (metastases) but were still alive at the end of follow-up.

A statistically significant association was observed among initial PSA values, rate of PSA change, and the development of lethal prostate cancer. However, these measurements were not accurate enough to predict cancer mortality. This was true regardless of the patient's initial PSA level or rate of PSA change.

"We conclude that PSA measurement is associated with prostate cancer prognosis and continues to be an important monitoring tool," Fall's team writes. "However, early PSA characteristics perform poorly in distinguishing those who develop a lethal prostate cancer from those at low or no risk of disease progression."

The team therefore concludes that "better decision tools are needed for active monitoring of patients with early disease."

SOURCE: Journal of National Cancer Institute, April 4, 2007.