Purpose: To explore the antitumor activity of the aromatase inhibitor, anastrozole, in the treatment of premenopausal women with hormone receptor-positive, metastatic breast cancer who have been rendered functionally postmenopausal with the use of the luteinizing hormone-releasing hormone agonist, goserelin.
Patients and methods: Premenopausal women with estrogen and/or progesterone receptor-positive, metastatic or recurrent breast cancer were enrolled in this prospective, single-arm, multicenter phase II trial. Patients were treated with goserelin 3.6 mg subcutaneous monthly and began anastrozole 1-mg daily 21 days after the first injection of goserelin. Patients continued on treatment until disease progression or unacceptable toxicity.
Results: Thirty-five patients were enrolled of which 32 were evaluable for response and toxicity. Estradiol suppression was assessed, with mean estradiol levels of 18.7 pg/mL at 3 months and 14.8 pg/mL at 6 months. One participant (3.1%) experienced a complete response, 11 (34.4%) experienced partial response, and 11 (34.4%) experienced stable disease for 6 months or longer for a clinical benefit rate of 71.9%. Median time to progression was 8.3 months (range, 2.1 to 63+) and median survival was not been reached (range, 11.1 to 63+). The most common adverse events were fatigue (50%), arthralgias (53%), and hot flashes (59%). There were no grade 4 to 5 toxicities.
Conclusion: The combination of goserelin plus anastrozole has substantial antitumor activity in the treatment of premenopausal women with hormone receptor-positive metastatic breast cancer.