Formestane Preferred as Second-Line Therapy in Advanced Breast Cancer

In 1993, formestane emerged as a preferred second-line treatment for advanced breast cancer in postmenopausal women, due to its effectiveness and better tolerability compared to aminoglutethimide. As an irreversible aromatase inhibitor, formestane reduced estrogen levels, which is crucial as tumors often develop resistance to tamoxifen. Recommended at 250mg intramuscularly every two weeks until disease progression, it showed response rates of 25 to 30%, with complete responses up to 15%, and response durations ranging from 5 to over 14 months. Notably, 80% of patients experienced no adverse effects, with the most common being a local reaction at the injection site. Unlike aminoglutethimide, formestane did not require corticosteroid supplements. Despite its higher cost and the need for intramuscular injections, formestane's favorable profile made it a better choice than aminoglutethimide, although it was not suitable as adjuvant therapy in operable breast cancer or for premenopausal women.