Activity of formestane in de novo tamoxifen-resistant patients with metastatic breast cancer.

In order to assess the feasibility of a sequential hormonal treatment after tamoxifen failure, 24 postmenopausal advanced breast cancer patients (median age 60 years; ECOG PS < or = 1) were treated with formestane (4-hydroxyandrostenedione) 250 mg i.m. fortnightly; 19 patients were estrogen receptor-positive. The sites of metastatic disease were soft tissue in 22 patients, viscera in 9 and bone in 18. The patients were considered evaluable for tumor response after four doses of formestane. Objective responses were observed in 8/24 patients (33%) with one complete and seven partial responses. The median response duration was 9.5 months. The complete response was obtained on skin. We conclude that although the number of complete responses appears to be unsatisfactory, de novo tamoxifen-resistant breast cancer patients are suitable for further hormonal treatment with formestane.