TUESDAY, July 26 (HealthDayNews) -- The answer to the biggest question in prostate cancer therapy -- which cancers need aggressive treatment and which are best left to "watchful waiting" -- may lie in the results of the prostate-specific antigen (PSA) test, two studies indicate.

But current practice, which relies on the PSA level gleaned from a single test, may need some tinkering, said Dr. Stephen J. Freedland, leader of one of the studies.

Instead, increases in PSA occurring over a series of tests appear crucial in gauging cancer risk, he explained.

"A single reading is like looking at one snapshot of a race," said Freedland, a clinical instructor in urology at the Johns Hopkins Hospital in Baltimore. "Watching the PSA change over time gives you a much better picture."

The rate at which PSA levels doubled over time was a critical factor for predicting death in a group of 379 men who underwent surgery for prostate cancer, concludes a report by Freedland's group published in the July 27 issue of the Journal of the American Medical Association.

"These preliminary findings may serve as useful guides to patients and their physicians to identify patients at high risk for prostate cancer-specific mortality ...[and] to enroll them in early aggressive treatment trials," they wrote.

A second paper in the same journal found similar results for a much more common scenario -- men treated with radiation after being diagnosed with prostate cancer.

The crucial factor predicting death in the 358 men in that trial was a two-point rise in PSA readings. Of the 30 deaths in the study, 28 occurred in men whose PSA rose by more than two points in the year before diagnosis.

"The PSA test has come under a lot of scrutiny because people have been looking at levels, rather than changes in levels," said lead researcher Dr. Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston. "This change in PSA of two points heralds the fact that the disease is beyond the prostate and needs more than prostate treatment."

For men, the reports have implications that start with their annual physical exam, D'Amico said. A PSA test should be part of that exam, and an increase of two points from the original level, no matter how high or low, indicates that a biopsy should be done to detect cancer, he said.

"You need to trace your PSA, not just where it is at, but where it is going," D'Amico said.

Once cancer is detected, aggressive treatment may be advisable for those men who experienced a two-point PSA increase before diagnosis, he said. Specifically, hormonal therapy should be added to other standard treatments, such as radiation therapy. In a previous study, hormonal therapy halved the death rate over seven years, D'Amico said.

The situation is different for men whose cancer recurs after surgery, Freedland noted. "Step one is to guess who to treat, and the PSA test can show that," he said. "Step two is how to treat them, and we're not there yet."

But for men newly diagnosed with prostate cancer, "the standard of care is going to be different because of PSA reading," D'Amico said. "Even though the level is low, a two-point increase indicates that more than radiation is needed to affect a cure."

More information

For more on prostate cancer, head to the National Cancer Institute.

SOURCES: Stephen J. Freedland, M.D., clinical instructor, urology, Johns Hopkins Hospital, Baltimore; Anthony D'Amico, M.D., Ph.D, chief, radiation oncology, Brigham and Women's Hospital, Boston; July 27, 2005, Journal of the American Medical Association

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