Antigen May Predict Cancer Survival

How long will a man with advanced prostate cancer survive? That may be related to how low his PSA level drops after androgen-deprivation therapy.

The finding comes from University of Michigan researcher Maha Hussain, M.D., and colleagues. They're conducting a study of men newly diagnosed with prostate cancer that has spread to other parts of their bodies. For men with this deadly metastatic cancer, it is big news.

It depends on a simple blood test. Prostate cells — especially prostate cancer cells — give off a marker called PSA (prostate-specific antigen).

After seven months of androgen-deprivation therapy, which is standard treatment for metastatic prostate cancer, men with low PSA levels have only one-fourth the chance of dying as men with higher PSA levels. Those with undetectable PSA levels have only one-fifth the risk of death as men with higher PSA levels.

"Low or undetectable PSA after seven months of androgen-deprivation therapy is a powerful predictor of risk of death in patients with new metastatic prostate cancer," Hussain said in a news release. "These findings could help patients avoid ineffective treatment."

Metastatic prostate cancer is usually fatal. Some patients die quickly. Others survive for years. Until now, there's been no reliable way to tell a patient which group he's in.

Standard treatment for spreading prostate cancer is to give a man a drug that blocks male hormones. It's called androgen-deprivation therapy. It's not a cure. Eventually, the body becomes resistant to the drug. But treatment fails earlier in some men than in others.

Now there may be a way to predict this treatment failure. Hussain and colleagues studied 1,345 men who were on androgen-deprivation therapy for seven months.

The men whose PSA levels stayed above 4.0 ng/mL survived only 13 months on average after the seven months of treatment. The men whose PSA levels were 4.0 ng/mL or less but more than 0.2 ng/mL survived an average 3.5 years. And the men whose PSA levels were undetectable (less than or equal to 0.2 ng/mL) lived for six years.

The findings could also provide what the researchers call a "window of opportunity" to test new treatments for advanced prostate cancer.
Hussain and colleagues are now testing whether successful androgen-deprivation therapy can be prolonged by stopping and starting treatment after the seven-month "induction" period.

The study appears in the Aug. 20 issue of the Journal of Clinical Oncology.

SOURCES: Hussain, M. "Journal of Clinical Oncology", Aug. 20, 2006; Vol .24: pp. 3984-3990. News release, University of Michigan Health System.

By Daniel DeNoon
Reviewed by Louise Chang