Conventional wisdom would have it that when results of a major trial are released, and those results strongly encourage a change in the standard of care, then physicians will ultimately make the switch in their treatment approaches. Seven years ago, data from the 8,000-man Prostate Cancer Prevention Trial showed that finasteride (Propecia) was effective in reducing the incidence of prostate cancer. Unfortunately, primary care physicians and urologists in the veterans' healthcare system have not yet gotten the message about the value of finasteride as chemoprevention.
Robert J. Hamilton, MD, Linda S. Kinsinger, MD, MPH, and colleagues looked at trends on monthly new and total prescriptions for finasteride within the Veterans Affairs (VA) system from 2000 to 2005. They wanted to determine how these prescription trends correlated with the 2003 publication of PCPT results (see Table 1).
Dr. Kinsinger is the chief consultant for preventive medicine at the Veterans Health Administration National Center for Health Promotion and Disease Prevention in Durham, N.C. Her coauthors are from the same institution and the department of surgery at the University of Toronto.
The study was conducted in two parts. First, the researchers analyzed prescriptions for 5 mg finasteride or 0.5 mg dutasteride (Avodart) from the VA pharmacy benefits database. Because dutasteride prescriptions made up less than 1% of all 5-a reductase inhibitors (5-ARI), the term "finasteride" was used to refer to both drugs in this study, the authors explained (Cancer Epidemiol Biomarkers Prev online, August 10, 2010).
The second part consisted of a Webbased survey sent to 1,072 primary care physicians (PCPs) and urologists in the VA system. The survey included questions on practice patterns for the diagnosis and treatment of benign prostate hyperplasia (BPH), knowledge of issues surrounding finasteride use in BPH or for cancer prevention, and the use of finasteride as a preventive medication.
The primary outcome for the study was changes in new finasteride prescriptions over time. The authors found that 237,286 patients had new prescriptions for the drug in the study time period. The use of finasteride increased, although the number of new users per month after publication of the PCPT results was less than expected and not statistically significant (P = .45). Also, the number of finasteride prescriptions given as chemoprevention did not change significantly post-PCPT results publication (P = .76).
For the survey, 43.3% of the invited PCPs and 44.7% of the invited urologists responded. Urologists reported prescribing finasteride more often than PCPs, although 64% of those urologists said they never considered it as a chemopreventive, citing the induction of high-grade tumors as the main reason. Among the PCPs, 80% said they never prescribed finasteride as chemoprevention and 52% reported that they did not know the drug could be used in this manner.
One reason for this lack of interest or awareness among the surveyed physicians could be the format in which trial results were presented, the authors suggested. Both the benefits and the harms of finasteride for chemoprevention were discussed in PCPT results, and the effect was different on PCPs and urologists: "PCPs did not seem to hear the message at all, and the urologists heard mostly the potential harms," they wrote.
Of the physicians who did prescribe finasteride, the majority reserved it for those patients they perceived as being at high risk for prostate cancer. Dr. Kinsinger's group noted that the respondents rated moderate to severe BPH as having the greatest influence in their prescription decision. But "BPH is not a risk factor for prostate cancer," the authors pointed out. "Physicians indicated this as a more influential factor than known prostate cancer risk factors such as family history, African-American race, and elevated prostate-specific antigen [PSA]."
The authors outlined some of the data they did not assess with this study: They did not explore whether physicians understood the difference between finasteride and the relative risk for high-grade tumors (27%) vs the much lower absolute risk (1.3%). Also, at the time of the study, physicians may have been reluctant to prescribe chemoprevention because of a lack of clinical guidelines. The American Society of Clinical Oncology (ASCO) and the American Urological Association have recently developed such guidelines (see Table 2).
The authors noted that the recent Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial of 6,729 men found a 23% reduction in the risk of prostate cancer with dutasteride, but these results were published after the current study was conducted.