PANEL CAUTIOUS ON BREAST CANCER DRUG

The nation’s leading group of cancer specialists said Sunday that it was premature for post-menopausal women with early breast cancer to switch to a newer class of drugs from tamoxifen, the drug that has long been the standard in preventing recurrence. Tamoxifen has been the standard therapy for the last 16 years and should remain so, the American Society of Clinical Oncology said in a strongly worded report. The panel rejected a switch to anastrazole, which is sold under the brand name Arimidex.

The question of switching arose in December when researchers reported preliminary findings from a current study that aims to compare Arimidex with tamoxifen over five years among more than 9,300 women. Among the first group of women to complete 33 months of treatment, Arimidex appeared to be slightly more effective and safer than tamoxifen.

The oncology society appointed an 18-member panel to assess the effectiveness and safety of Arimidex. The panel unanimously agreed that the findings were encouraging, but that 33 months was too short a period to judge the safety and effectiveness of aromatase inhibitors as a standard prevention for recurrence of breast cancer among post-menopausal women.

Dr. Larry Norton, breast cancer specialist at Memorial Sloan-Kettering Cancer Center in New York and society president, said there are still unknowns about aromatase inhibitors. One is whether these drugs will behave like tamoxifen, which continues to have beneficial effects after it is stopped. Another reason for not recommending the switch is that tamoxifen takes five years to gain its full effect; so it is conceivable that five years of anastrozole could be inferior to five years of tamoxifen. Additionally, some of tamoxifen’s toxic effects, like an increased risk of cancer of the uterus, were not identified until the drug had been in use for many years. Although the panel was concerned about being criticized for being too conservative, they were more concerned about the possibility of putting women at risk

A wealth of information about the role of drugs that inhibit aromatase, an enzyme that the body requires to make estrogen, is expected to come over the next few years. The panel will review the findings yearly. The FDA has approved the marketing of Arimidex and two other aromatase inhibitor drugs, Femara (letrozole) and Aromasin (exemestane), for the treatment of advanced breast cancer.