Megestrol acetate in advanced breast carcinoma after failure to tamoxifen and/or aminoglutethimide

Seventy-three patients with metastatic breast cancer, whose disease progressed on hormonal therapy with tamoxifen or aminoglutethimide, were treated with megestrol acetate, 160 mg/day. No complete responses were observed. Partial response was achieved in 3 patients (4%), for a median of 9 months (range 5-13). Thirty-five patients (48%) remained stable, for a median of 8 months (3-26). The remaining 35 patients (48%) had clear progression of their metastatic disease on therapy. Response to megestrol acetate was achieved in patients with metastases in bone and pleura only. There was no correlation between response to megestrol acetate and response to prior chemotherapy, prior tamoxifen therapy, previous treatment with aminoglutethimide, or hormone receptor status. The actuarial 24-month survival for all patients was 37%. The main side effects of megestrol acetate included weight gain (20% or over), pruritus, elevation of blood pressure, weakness, and vaginal bleeding; they were only occasionally observed. The objective improvement observed during this trial is disappointing; the only reasons to justify the use of megestrol acetate as second- or third-line hormonal therapy in patients with metastatic breast cancer, would be the relatively long duration of disease stabilization in a large proportion of patients, and the low toxicity observed with the drug.