Tamoxifen Standard for Preventing Breast Cancer Recurrence

ASCO—Although aromatase inhibitors show promise for preventing recurrence following surgery in women with hormone-receptor-positive breast cancer, tamoxifen (Nolvadex) remains the standard of care, according to an evidence-based technology assessment of the aromatase inhibitors, sponsored by the American Society of Clinical Oncology. The ASCO expert panel found that the available data on aromatase inhibitors for this indication do not support routine use outside of clinical trials.

"While recent findings on aromatase inhibitors are encouraging, data on long-term use of the drugs are needed before a change in the standard of care is justified," Eric Winer, MD, of Dana-Farber Cancer Institute and chair of the panel, said at a press briefing at the 38th Annual ASCO Meeting.

The panel assessed the medical literature and the preliminary findings from the ATAC study (Arimidex, Tamoxifen Alone or in Combination) presented last year at the San Antonio Breast Cancer Symposium. ATAC showed that the aromatase inhibitor anastrozole (Arimidex) may be more effective than tam-oxifen at preventing recurrence in postmenopausal early-stage breast cancer patients after surgery. Median follow-up on the ATAC trial is currently 33 months.

The panel concluded that because a 5-year course of therapy is required for tamoxifen to provide its greatest clinical benefit, the data on anastrozole are not sufficiently long-term to appropriately compare the two drugs. It is also possible, they said, that long-term use of anastrozole may lead to unexpected side effects. In contrast, there is extensive long-term follow-up data on patients treated with tamoxifen and a clearer understanding of its associated risks.