Tuesday, August 10, 2010

Changing thinking about preventing cancer with drugs will take time

Finasteride has been shown to reduce the risk of
prostate cancer, but few doctors prescribe it for
that purpose.
PHILADELPHIA – (Cancer Digest) A new survey shows that doctors have not increased their use of finasteride for prostate cancer prevention despite the 25 percent reduction in prostate cancer among those taking the drug shown in the Prostate Cancer Prevention Trial (PCPT) seven years ago.

Led by Dr. Ian Thompson, chairman of the department of urology at the University of Texas Health Science Center, this new study shows that physicians have not changed their practice patterns, with 64 percent of urologists and 80 percent of primary care physicians never prescribing finasteride for chemoprevention. Finasteride is approved and commonly prescribed for the treatment of enlarged prostate, or benign prostatic hypertrophy (BPH).

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 study is published in the September issue of the Journal of the American Association for Cancer Research.

Thompson thinks he knows why. The early study analysis also showed that the drug was linked to a 27 percent increase in high-grade disease. That puzzling result received the most attention in doctor reviews of the study, and apparently hasn't been forgotten despite a subsequent 2008 study in which Thompson and colleagues reanalyzed the data from the 18,000 men in the PCPT along with the available tumor biopsies. Results of that study showed that finasteride did not actually increase risk of high grade disease; it just made the available testing more sensitive.

“People tend to read editorials more than they read actual journal articles,” Thompson said in a prepared statement. “The study paradox of a reduction in overall disease, but an increase in high-grade disease was not explored until much later.”

Dr. Linda Kinsinger, 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 following the PCPT trial only 2 percent of the doctors surveyed said they had been influenced by the findings in PCPT. 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.”

In explaining the difficulty, Thompson pointed to the revolution in prevention of artery disease following the dramatic cholesterol-lowering results of prescribing statins. Cholesterol levels were driven down with little to no side effects thus reducing the risk of cardiovascular disease. Thompson says the difference with statins and finasteride for preventing disease lies in the measurability of statin use.

“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.”

Consequently, Thompson says chemoprevention for cancer is a new frontier that  will take time to establish among the medical community.

SOURCE: adapted from press materials provided by the American Cancer Research Association

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