Abstract
In a prospective, randomized trial Cancer and Leukemia Group B (CALGB) evaluated CAF chemotherapy (cyclophosphamide + doxorubicin + 5-fluorouracil [5-FU]) v CAF plus tamoxifen (TCAF) in advanced breast cancer. Patients were stratified by estrogen receptor (ER) status, dominant site of metastatic disease, menopausal status, and prior adjuvant therapy. Regardless of ER status or menopausal status, the addition of tamoxifen conferred no significant advantage in response rate, response duration, time to treatment failure (TTF) or survival over CAF alone. A secondary objective was to compare the response to CAF of ER positive (ER+) and ER negative (ER-) patients to determine if there was a differential response to cytotoxic chemotherapy. Response rates of ER+ and ER- patients to CAF were identical (56%), but the response duration, time to treatment failure, and survival of ER+ patients were significantly longer than ER- patients. This lack of differential response implies that chemotherapy and hormonal therapy may compete for the same pool of ER+ cells. It also suggests that chemotherapy kills breast cancer cells indiscriminately, regardless of ER status.