Recent research revealed that the drug finasteride, commonly used to treat enlarged prostates, decreases the risk of prostate cancer by nearly 25 percent. When the original results of the study, known as the Prostate Cancer Prevention Trial, were initially released in 2003, the good news was tempered by the fact that the study also revealed a small but statistically significant increase in the number of aggressive, high-grade prostate tumors in the men from the study who were taking finasteride. But two new analyses of the study's data show that finasteride decreases the risk of all types of prostate cancer, even for those men with high-grade tumors.
Prostate Cancer Prevention Trial
Sponsored by the National Cancer Institute, the Prostate Cancer Prevention Trial (PCPT) was designed to determine if finasteride could prevent prostate cancer in older men. Available in both brand-name and generic forms, finasteride works by blocking the conversion of the hormone testosterone to dihydrotestosterone, a hormone that fuels the growth of all prostate cancers. The drug was developed to treat benign prostatic hyperplasia (BPH), a condition affecting older men in which the prostate enlarges, making urination difficult. Begun in 1993, the randomized, multicenter study followed approximately 19,000 men aged 55 and older, half taking finasteride pills on a daily basis, the other half taking a placebo. Neither the study participants nor their physicians knew who was taking finasteride or the inactive placebo.
The study was halted early in March 2003 when it was determined through the use of annual PSA screenings and digital rectal exams that men taking finasteride were 25 percent less likely to develop prostate cancers than men taking placebos. The results were as follows: 18 percent of men taking finasteride developed prostate cancer versus 24 percent of men taking placebo.
Troubling High-Grade Tumor Results
A note of discord was introduced, however, when it was determined that while finasteride reduced the overall risk of prostate cancer, it also appeared to cause a slight increase in the incidence of the high-grade forms of the disease, which are defined as tumors with Gleason scores of 7 to 10. (The Gleason grading system characterizes the aggressiveness of prostate cancer, providing an estimate of the cancer's potential to grow and spread to other parts of the body, where it is more difficult to treat successfully.) The increase in high-grade tumors -- 6.4 percent of the men in the finasteride group versus 5.1 percent of the men taking placebo -- was considered small but significant.
As a result, few physicians recommended using finasteride as a prostate cancer prevention drug, basing this decision on the belief that the drug was preventing harmless prostate cancers that would never require treatment while potentially encouraging the deadlier versions. Still, the study's researchers wondered if the increased number of high-grade tumors was due to the fact that finasteride was shrinking the prostate, making it easier for doctors to find aggressive, high-grade tumors during needle biopsies.
