A Better Way To Gauge Prostate Cancer Risk?

A team of American researchers has developed a "risk calculator" that they say is a better tool for predicting a man's odds of developing prostate cancer than prostate-specific antigen blood testing alone.

The calculator - posted online for use by both patients and physicians - adds age, race, family history of prostate cancer, prior biopsy findings and digital rectal exam results into the mix alongside PSA levels to assess a man's risk before having a new biopsy.

"PSA is a very important predictor of cancer, but is only one part of the picture of a man's risk of cancer," explains study author Dr. Ian M. Thompson, professor and chairman of the department of urology at the University of Texas Health Science Center in San Antonio.

His team describes the new screen in the April issue of the Journal of the National Cancer Institute.

According to the American Cancer Society, prostate cancer is the second leading cancer killer for men. An estimated one in six men will receive a prostate cancer diagnosis in their lifetime, and more than 30,000 Americans currently die of the disease each year.

For healthy men over the age of 50, the ACS now recommends an annual PSA blood test, as well as a digital rectal exam. The organization advises that men at higher risk -- such as blacks and patients with a history of prostate cancer in their family -- begin such testing at age 45.

While 50 percent of older men now undergo routine PSA screenings, Thompson says his prior work suggests that PSA results are more useful when taken in context with other factors. Too often, he says, PSA levels are interpreted as black-and-white indicators of either "normal" or "elevated" risk status. The truth is that rising PSA levels reflect a more graduated increase in cancer risk.

Looking for a more accurate method, Thompson and his colleagues collected data from more than 5,500 healthy men over the age of 55 who had participated in a large-scale prostate cancer prevention trial.

For a period of seven years, all the men underwent annual PSA and digital rectal exam testing, and well as having at least one prostate biopsy conducted over the study period. By the study's end, nearly 22 percent of the men went on to develop prostate cancer, and 5 percent developed high-grade disease.

At the seven-year mark, the researchers fed a combination of accumulated data -- biopsy findings, patient age, race, family history of prostate cancer, previous biopsy history, along with PSA levels and DRE results - into their "statistical risk models."

Thompson's team found that a family history of prostate cancer, or an abnormal result from the PSA or DRE test, were all strongly associated with an increased risk for prostate cancer.

Race and age also figured in the equation, with blacks and older men at relatively high risk for prostate cancer.

Having had a prior negative biopsy result was found to be associated with a decreased risk for the disease.

By compiling such patient variables together, the Texas group say they were able to develop a prostate risk calculator that provides better predictive accuracy than an analysis of PSA levels alone.

"This study provides a way to integrate other important risk factors to allow men and their doctors to better understand their risk and make a more intelligent decision whether to proceed with further testing," Thompson says.

But in an accompanying editorial, Dr. H. Ballentine Carter, of the Johns Hopkins School of Medicine, cautioned that the calculator's current design fails to distinguish between slow-growing cancers and more life-threatening varieties.

This, he says, could lead to a rash of unnecessary biopsies.

Robert Smith, director of cancer screening at the American Cancer Society, says the new model has its pros and cons.

"It does not distinguish between significant and not-significant disease, so the calculator provides some help, but not enough help," he says. "But it also allows an individual to take their PSA level and actually interpret it in the context of some other information based on the experience of a large number of men, to understand what is the likelihood that they have prostate cancer. So I think it could actually be useful."

A second study, also published in the April of the same journal, suggests that new prostate cancer treatments currently undergoing clinical trials could be better and more quickly assessed by tracking ongoing changes in patients' PSA levels, rather than by waiting to tally long-term patient survival.

The team of Columbia University researchers working at New York-Presbyterian Hospital/Columbia in New York City based their conclusions on an analysis of the progress of 551 men undergoing a new treatment for prostate cancer.

They found that a 30 percent drop in PSA levels in the first three months of treatment correlated with a 50 percent drop in their risk of death -- a "surrogate" marker that could be used in place of the usual endpoint, survival. Use of this marker might mean a treatment's effectiveness could be evaluated much earlier.

The researchers noted that the U.S. Food and Drug Administration currently bases its "endpoint" assessment of a given treatment's success solely on long-term patient survival.