Hormonal treatment for metastatic breast cancer. An eastern cooperative oncology group phase III trial comparing aminoglutethimide to tamoxifen

Background. Tamoxifen and aminoglutethimide are two hormone therapies reported to be effective palliative approaches for patients with metastatic breast cancer. The current trial was designed to evaluate their relative therapeutic effectiveness. Methods. Two hundred forty-nine postmenopausal women with advanced breast cancer were randomized in an Eastern Cooperative Oncology Group (ECOG) Phase III study to treatment with adrenalectomy, aminoglutethimide, or tamoxifen with crossover to alternate therapy if disease progressed. Adrenalectomy was dropped as a treatment after 2 years because of low patient accrual. Results. There were 216 evaluable patients entered in the study with 108 initially randomized to aminoglutethimide and 108 to receive tamoxifen therapy. The overall response rate for aminoglutethimide was 45%, and for tamoxifen it was 27%. One institution had a response rate of 60% with aminoglutethimide and only 4% with tamoxifen, whereas all of the other institutions combined had a response rate of 41% with aminoglutethimide and 34% with tamoxifen. Eighty-seven evaluable patients crossed over to the other drug (44 to aminoglutethimide and 43 to tamoxifen). There was a 36% response rate to aminoglutethimide and 19% to tamoxifen. with stable disease in 36% of both groups. The overall survival rates were identical. Toxicity was greater with aminoglutethimide (dermatitis) but was not life-threatening. Glucocorticoid support with either dexamethasone or hydrocortisone was acceptable. Conclusions. Both aminoglutethimide and tamoxifen produced responses in postmenopausal patients with breast cancer, and a significant number of crossover responses were observed. Of interest in this randomized study was the observation that one institution had a markedly different response rate on induction, reinforcing the need for multi-institution trials in Phase III studies.