Despite the dramatic results of the Prostate Cancer Prevention Trial (PCPT), which showed a significant reduction in prostate cancer among those taking finasteride, physicians have not increased its use, according to a study published in the September issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
The first results of the PCPT were published in 2003 in The New England Journal of Medicine and were widely reported. The randomized controlled trial consisted of 18,000 men and showed a 25 percent reduced risk of prostate cancer.
Unfortunately, it also showed a 27 percent increased risk in high-grade tumors, which was noted in an accompanying editorial. Ian Thompson, M.D., chairman of the department of urology at the University of Texas Health Science Center, who led the study, said the editorial may have colored the perception of finasteride.
"People tend to read editorials more than they read actual journal articles," said Thompson. "The study paradox of a reduction in overall disease, but an increase in high-grade disease was not explored until much later."
In 2008, another report was published in Cancer Prevention Research, another journal of the AACR, where Thompson and colleagues reanalyzed the data along with the available tumor biopsies. Results showed that finasteride did not actually increase risk; it just made the available testing more sensitive. This result confirmed the benefits of finasteride for prostate cancer prevention.
However, results of this new study showed that physicians have not changed their practice patterns.
Linda Kinsinger, M.D., M.P.H., chief consultant for preventive medicine at the Veterans Health Administration National Center for Health Promotion and Disease Prevention, and colleagues surveyed 325 urologists and 1,200 primary care physicians to determine their prescribing patterns.
Although the number of men starting finasteride grew over a five-year period, the publication of the PCPT trial did not influence their decision. Fifty-seven percent of urologists and 40 percent of primary care physicians said they prescribed finasteride more often; only 2 percent said they had been influenced by the findings in PCPT.
In fact, 64 percent of urologists and 80 percent of primary care physicians never prescribe finasteride for chemoprevention. When asked for reasons for their decision, 55 percent said they were concerned about the risk of high-grade tumors and 52 percent said they did not know it could be used for chemoprevention.
"The use of finasteride for prostate cancer prevention does not appear to be widely endorsed," said Kinsinger. "The concept of chemoprevention is a difficult one for patients and physicians."
At the American Association for Cancer Research 101st Annual Meeting 2010 in Washington, D.C., researchers presented results of the STAR trial, which showed a reduction in breast cancer with raloxifene use. In turn, experts discussed the implications of raloxifene for breast cancer prevention. Scott Lippman, M.D., chair of the Department of Thoracic/Head and Neck Medical Oncology at the University of Texas M. D. Anderson Cancer Center and editor-in-chief of Cancer Prevention Research, and Judy E. Garber, M.D., M.P.H., director of the Cancer Risk and Prevention Program at Dana-Farber Cancer Institute and AACR president-elect, said the public needs to think about agents like raloxifene in the same manner that they would think about statins in heart disease prevention.
Statins revolutionized the treatment of heart disease by driving cholesterol levels down with little to no side effects and thus reducing the risk of cardiovascular disease. Thompson said the statin to chemoprevention analogy is a good one, but presents an important challenge.
"Statins lower heart disease by reducing blood cholesterol and affecting other lipids, effects which are easy to measure," he said. "There is no equivalent biomarker for cancer prevention. With cholesterol, for example, you can tell that the statin is working. With a cancer chemoprevention agent, you cannot measure success except with the absence of cancer, which you weren't expecting to get anyway."
Thompson agreed, however, that chemoprevention is an important new frontier that needs continued emphasis.