Continuing Education Program #08CE059d • RELEASE DATE: November 15, 2008 • EXPIRATION DATE: November 14, 2009 C O M M E N TA R Y
Finasteride and Prostate Cancer Prevention: The Latest Chapter: A Pharmacist’s Perspective BY HELEN MCFARLAND, PHARMD, BCOP Union Memorial Hospital, Baltimore, Maryland
he Prostate Cancer Prevention Trial (PCPT) was the largest prostate cancer prevention trial ever completed.1 The positive results were tainted by the increased incidence of high-grade tumors found in the finasteride arm, thus muting the enthusiasm of the medical community to use finasteride as a preventative agent. The current reanalysis of the PCPT data presented in the Redman article is one of many attempts to evaluate the PCPT results to determine the real role of finasteride as a preventative agent for prostate cancer. Redman and colleagues used advanced statistical modeling to determine whether finasteride is truly increasing the risk of high-grade tumors or if there are other factors that are lending bias to the interpretation of the data. The authors thoroughly discuss the difference between the original data and their findings and conclude that finasteride does not increase the risk of high-grade prostate cancer after 7 years of therapy. The PCPT investigators suggest that finasteride increases the sensitivity of prostate-specific antigen (PSA) and digital rectal examination (DRE) for detecting prostate cancer.2,3 Finasteride decreases the prostate gland volume, therefore if there was tumor present, it would be easier to detect by DRE or biopsy. Finasteride decreases PSA levels to a greater extent in the setting of benign prostatic hyperplasia, thus those men receiving finasteride with persistently elevated PSA levels are more likely to have prostate cancer, and the risk of high-grade disease increases proportionally with higher PSA levels. When the PCPT data
were adjusted for prostate gland size, the biopsy results showed there was no increase in highgrade tumors in the finasteride group.2 The amount of data that has been released which contradicts the original conclusion of the 2003 PCPT data certainly has offered some clarification of the risks and benefits of finasteride for prostate cancer prevention. Patients and providers should feel comfortable that finasteride in the preventive setting is not selecting out for high-grade tumors. So what is the final recommendation for the use of finasteride in prostate cancer prevention?
Patients and providers should feel comfortable that finasteride in the preventive setting is not selecting out for high-grade tumors. The American Urological Association and the American Society of Clinical Oncology have yet to make formal recommendations on the subject. The most common side effects reported in the PCPT finasteride group were sexual dysfunction (reduced ejaculate volume, erectile dysfunction, and decreased libido) and gynecomastia. Older age predicts increased sexual dysfunction with finasteride. The increase in adverse effects in the finasteride arm was small
and decreased over the 7 years of treatment.4 Patients in the PCPT received finasteride 5 mg orally every day for up to 7 years of therapy. Additional studies are required to determine the minimally effective duration of therapy to decrease potential adverse effects. Thompson and colleagues developed a risk calculator taking into account variables such as PSA, DRE, age, race, family history, and history of a prior negative biopsy.5 The calculator predicts a patient’s risk for developing prostate cancer and risk of high-grade disease. Use of these results in combination with consideration of the risks and potential benefits of finasteride therapy should be part of the counseling session with all men older than 55 years of age. This can assist the patient in determining the best course of action based on the potential aggressiveness of his disease and potentially decrease unnecessary systemic therapy in tpatients with low-risk disease. References 1. Thompson IM, Goodman PJ, Tangen CM, et al. The influence of finasteride on the development of prostate cancer. N Engl J Med. 2003;349:215-224. 2. Yael CC, Liu KS, Heyden NL, et al. Detection bias due to the effect of finasteride on prostate volume: a modeling approach for analysis of the prostate cancer prevention trial. J Natl Cancer Inst. 2007;99:1366-1374. 3. Thompson IM, Chi C, Ankerst DP, et al. Effect of finasteride on the sensitivity of PSA for detecting prostate cancer. J Natl Cancer Inst. 2006;98:1128-1133. 4. Moinpour CM, Darke AK, Donaldson GW, et al. Longitudinal analysis of sexual function reported by men in the prostate cancer prevention trial. J Natl Cancer Inst. 2007;99:1025-1035. 5. Thompson IM, Ankerst DP, Chen C, et al. Assessing prostate cancer risk: results from the prostate cancer prevention trial. J Natl Cancer Inst. 2006;98:529-534.
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