乌鸦传媒

ALEXANDRIA, Va., Feb. 25 -- Millions of healthy men ages 55 and older should talk to their physicians about taking a 5-alpha reductase inhibitor such as finasteride (Proscar) or dutasteride (Avodart) to prevent prostate cancer, according to a guideline issued by two medical groups.

The recommendation applies to men who have prostate specific antigen values ≤3 ng/mL, who plan to be screened annually, and who have no signs of prostate cancer.

The recommendation does not constitute an endorsement of finasteride or any other 5-ARI for prostate cancer prevention, said NIH scientist Barnett S. Kramer, M.D., who chaired the guideline panel representing the American Society of Clinical Oncology and the American Urological Association.

"The recommendation is not that they take finasteride but that the health issue is important enough that a discussion, as part of a periodic check-up, is worthwhile, and many men will choose not to take finasteride and others will choose to take it," Dr. Kramer said during an ASCO press briefing.

"People make personal decisions not only on evidence but on what their own concerns are and personal tradeoffs," he added.

The guideline panel based the recommendation on three key findings that emerged from a review of published data:

The bulk of the evidence came from publications related to the Prostate Cancer Prevention Trial. The study of 19,000 healthy men ages 55 and older revealed a 26% reduction in the relative risk of prostate cancer in men randomized to take finasteride.

However, the principal result of the study got lost in controversy surrounding the finding of an increased risk of high-grade prostate cancer in the finasteride group.

Follow-up studies and publications essentially ruled out finasteride as a cause of high-grade cancers.

"Careful pathologic analysis of prostate specimens from men who developed cancer showed smaller tumors and less dangerous-appearing tumors with less invasion in the finasteride arm than in the placebo arm," said Dr. Kramer.

"Subsequent statistical analyses confirmed that finasteride was unlikely to have caused an increase in high-grade cancers."

The panel did not specifically mention finasteride in the recommendation, but 85% of the data on chemoprevention with 5-ARIs came from studies of that drug, he said.

A randomized trial of chemoprevention with dutasteride (Avodart) has yet to be completed. However, the panel reviewed available data from studies of dutasteride and found the results consistent with those involving finasteride.

Dr. Kramer emphasized that the recommendation pertains only to men who are already being screened regularly for prostate cancer or who plan to have annual PSA testing.

In summary, they wrote that "for the man who wishes periodic monitoring (opportunistic or organized screening), 5-ARI therapy during a 7-year period reduces the period prevalence of for-cause cancer diagnoses by approximately 25% (relative risk reduction) for an absolute risk reduction of about 1.4%.

Most of the panel felt that "the observed higher incidence of high-grade (Gleason score 8 to 10) cancer in the finasteride group is likely due to confounding factors; the increased incidence of high-grade cancer as a result of induction by the drug cannot be excluded with certainty."

The Census Bureau has estimated that 31 million men in the U.S. are 55 or older. Chemoprevention in such a large population has major implications for healthcare costs.

Dr. Kramer said chemoprevention with generic finasteride would cost about $1,000 a year. Given that cancer prevention is not an FDA-approved indication for the drug, insurers have no obligation to cover the cost.

Complete text of the guideline will be published in March in both the Journal of Clinical Oncology and the Journal of Urology.