Scientists have found a way to predict which cases of prostate cancer will turn out to be the most serious -- a tool that should help physicians decide when to take aggressive action against this generally slow-growing cancer of old age, researchers say in a report released today.
The researchers found that a dramatic surge in blood levels of a protein called prostate specific antigen, or PSA for short, in the year before diagnosis was linked to the greatest risk of death.
Patients with steep-rising PSA values probably require especially aggressive treatment and should not be managed by a regime of "watchful waiting," said the study's senior author, Dr. William J. Catalona, director of the clinical prostate cancer screening program at Northwestern Memorial Hospital in Chicago.
In addition, such a steep rise in PSA levels should warrant a biopsy even if the levels do not reach the currently accepted warning threshold, Catalona said.
Prostate cancer is the second-leading cancer killer of men. Each year, about 240,000 men are diagnosed with the disease and nearly 30,000 die of it, according to the American Cancer Society. Prostate cancer mostly strikes men over age 65, and its course is unpredictable. It often develops so slowly that patients can die of other conditions before the cancer has a chance to kill them. In other cases, its course is quick and more deadly.
The problem for doctors has been their inability to distinguish one from the other at an early stage.
Since the 1990s, doctors have been widely screening men with a blood test for PSA, a protein that leaks into the bloodstream when the prostate's biology goes awry. PSA testing has led to more and earlier diagnoses.
In the report, published in the current issue of the New England Journal of Medicine, Catalona and colleagues tracked 1,095 men with prostate cancer that had not yet spread beyond the gland. All had been treated by a radical prostatectomy, the surgical removal of their prostate glands. The men were tracked for an average of more than five years.
The scientists detected a significantly higher rate of recurrence and death in those men whose levels of PSA had increased by more than 2 nanograms per milliliter in the year before diagnosis. They recorded a nearly 10 times greater risk of death for those with fast-rising PSA levels, although for statistical reasons they cautioned that a precise increase in risk was still undetermined.
Dr. Charles E. Shapiro, staff urologist at the Kaiser Permanente Los Angeles Medical Center, said examining a patient's PSA changes could help customize treatments.
"What we need to be able to do is identify those tumors which are growing more quickly from those that are growing more slowly," he said.
Men whose PSA levels have been rising swiftly may be good candidates for radical prostatectomy and additional treatments such as hormone therapy or chemotherapy, experts said. Those whose PSA levels have remained constant may be more suitable for surgery without additional treatments, or a watch-and-wait approach.
However, the doctors acknowledged that stringent clinical trials were still needed to find out which treatments work best for each class of men.
The study also has implications for screening, said Dr. Mark H. Kawachi, director of the prostate cancer center at City of Hope in Duarte.
Currently, physicians generally wait until a PSA value has reached 4 nanograms per milliliter before ordering a biopsy. Today's study suggests that using an absolute value as a threshold for biopsy may not be valid, Kawachi said.