Formestane, a steroidal aromatase inhibitor after failure of non-steroidal aromatase inhibitors (anastrozole and letrozole): is a clinical benefit still achievable?

BACKGROUND: There are few clinical data on the sequential use of aromatase inhibitors (AI). This paper focuses on the relevance of clinical benefit CB (CR + PR + SD > or = 6 months) in postmenopausal metastatic breast cancer (MBC) patients treated with the steroidal aromatase inhibitor (SAI) formestane (FOR). who had already received non-steroidal aromatase inhibitor (nSAI): letrozole (LTZ) or anastrozole (ANZ). PATIENTS AND METHODS: Twenty postmenopausal women with MBC were analysed in this retrospective two-centre study with the sequence nSAI-FOR. When receiving ANZ, 1 of 11 achieved a complete response and 9 of 11 a stable disease > or = 6 months, and receiving LTZ 1 of 9 achieved a partial response and 4 of 9 a stable disease > or = 6 months. The analysis of the entire population treated with FOR showed an overall CB of 55% (11 of 20) with a median duration of 15 months and median time to progression (TTP) of 6 months.
CONCLUSIONS: Formestane 250 mg once bi-weekly seems to be an attractive alternative third-line hormonal therapy for the treatment of patients with MBC, previously treated with nSAI.