Within moments at a computer, a man 55 or older who is concerned about his chance of developing prostate cancer can obtain a trustworthy, science-based estimate of risk – information that can help him decide whether or not to see a physician.
That information could lead more men to seek earlier consultations about the disease, potentially reducing the 30,000 deaths attributed to prostate cancer annually in the U.S.
The new risk calculator, based on data from the National Cancer Institute’s Prostate Cancer Prevention Trial (PCPT) that ended in 2003, is described in the April 19 online edition of the Journal of the National Cancer Institute. Lead author Ian M. Thompson Jr., M.D., professor and chairman of urology at the Health Science Center, announced the new research April 18 in San Antonio.
The risk calculator goes beyond the prostate-specific antigen (PSA) test, which measures one prostate protein and for 20 years was thought to be the deciding indicator of whether a man should move forward with a prostate biopsy for cancer. Recent reports have indicated there is no “normal” range of PSA values, and that men are at risk of serious disease regardless of PSA level.
“A man who goes to see his doctor with a PSA report brings with him other factors that affect risk,” Dr. Thompson said. “If a man’s father died of prostate cancer, the doctor looks at him and is more worried. If a man is African American, the doctor looks at him and is more worried. If a man is African American and his father died of prostate cancer, the risk is that much greater, yet the men’s PSA reports may be exactly the same. Against that backdrop we did the study, which showed you can actually mathematically fold all of these risk factors together. Each of the risk factors that we analyzed turned out to be important in calculating a man’s risk.”
The PCPT tested whether the drug finasteride could prevent prostate cancer, and researchers found it did lower the risk by nearly 25 percent in the treatment group. Since that initial finding, PCPT data from 19,000 men have proved useful in studies of PSA and other topics.
Data from 5,519 men in the PCPT placebo group, each of whom had at least one biopsy as part of the trial, were used to construct the risk calculator. Biostatisticians and researchers from the Health Science Center, the Fred Hutchinson Cancer Research Center in Seattle and the National Cancer Institute created a statistical model of risk based on age, family history of prostate cancer, ethnicity (African Americans are at increased risk), previous normal or abnormal digital rectal exam, PSA level, and previous normal or abnormal prostate biopsy. The risk calculator is limited to men 55 to 95 because the PCPT enrolled only men in that age range.
“We think this has the potential to save many lives,” Dr. Thompson said. “It helps physicians communicate risk to their patients. The other thing it does is provide information to a patient so he can make up his own mind what to do.
“Let’s say two men with 17 percent risk estimates go to see their physicians. One man is not concerned about his risk, perhaps because of other medical problems. He opts to wait and have a prostate biopsy next year. The second man, whose next-door neighbor just died of prostate cancer, is very concerned, has never been checked before, and opts to have a prostate biopsy immediately. The amazing thing is both men are correct in their decisions. They have used their own personal priorities – the goals that they want to achieve from their medical care – to make an informed, intelligent decision. What this calculator does, instead of giving them a PSA number and ignoring all the other risk factors, is to provide very powerful information for each man to discuss with his physician.”
The risk calculator, at www.compass.fhcrc.org/edrnnci/bin/calculator/main.asp, will be refined as research provides new insights into prostate cancer. “Ultimately, we want to fold in other factors, such as biomarkers, blood tests, genes, height and weight,” Dr. Thompson said. “Our goal is to have a calculation that is very precise.”
Studies such as Dr. Thompson’s National Cancer Institute-funded SABOR project (San Antonio Center of Biomarkers of Risk for Prostate Cancer) will add new genetic and other risk factors to the calculator, he said. SABOR has enrolled more than 3,000 men; more than half are Hispanic.
Collaborators on the risk calculator study are from the Health Science Center, the Fred Hutchinson Cancer Research Center in Seattle, the University of Colorado and the National Cancer Institute. The Southwest Oncology Group provided administration for the PCPT.