CHICAGOGiving tamoxifen(Drug information on tamoxifen) concurrently with adjuvant chemotherapy halves the benefit of the chemohormonal combination compared to giving tamoxifen after completion of chemotherapy in postmenopausal patients with node-positive, hormone-receptor positive breast cancer (ASCO abstract 143). These initial results from North American Breast Intergroup Trial 0100 (INT 0100, SWOG 8814), presented by Kathy S. Albain, MD, are expected to establish a new standard of care for treating breast cancer in postmenopausal women.
Based on a median follow-up of 8.5 years, the intergroup data showed that giving tamoxifen concurrently with chemotherapy reduces both disease-free survival and overall survival compared to giving chemotherapy followed by tamoxifen.
"Concurrent chemotamoxifen may result in suboptimal benefit from this or similar chemotherapy programs, potentially cutting efficacy by as much as 50%. The results of INT 0100 support a new practice standard of starting adjuvant tamoxifen after chemotherapy is completed," Dr. Albain said. She is the trial’s lead investigator as well as director of breast cancer research and co-director of the Breast Care Center at Loyola University’s Cardinal Bernardin Cancer Center in Chicago.
Researchers had suspected that tamoxifen might interfere with the effects of cytotoxic chemotherapy because many currently used antineoplastic agents are cell-cycle dependent. Tamoxifen freezes tumor cells in the mitotic pathway, making them less vulnerable to cytotoxic agents.
Objectives and Stratification
Dr. Albain said that the first objective of this trial was to determine whether adding tamoxifen to anthracycline-based adjuvant therapy with CAF (oral cyclophosphamide(Drug information on cyclophosphamide) [Cytoxan, Neosar)/doxorubicin [Adriamycin]/fluorouracil) was superior to tamoxifen alone for treatment of breast cancer in postmenopausal women with node-positive and hormone-receptor positive disease. "Last year we reported a significant disease-free survival and overall survival advantage for the combination," she said.
The second objective, addressed in this year’s presentation, was to determine whether CAF followed by tamoxifen (CAF-T) was more effective than concurrent CAF-tamoxifen therapy (CAFT).