Duration of remission to ICI 182,780 compared to megestrol acetate in tamoxifen resistant breast cancer

Recently we reported that treatment with the specific (pure) antioestrogen, ICI 182,780, in 19 patients with advanced breast cancer resistant to tamoxifen resulted in a high response rate and a long median duration of remission (> 22 months). In order to assess the relative value of ICI 182,780 in this clinical situation we have compared its activity with that of megestrol acetate, the standard second-line endocrine therapy in a group of similarly selected patients. Each ICI 182,780 treated patient was matched with three patients who received megestrol acetate (n = 57). Both groups were previously treated with tamoxifen. Patients were matched for age, site of metastases, prior tamoxifen therapy (for adjuvant or advanced disease) and therapeutic response to tamoxifen where given for advanced disease and therapeutic response to second-line therapy (i.e. ICI 182,780 or megestrol acetate). The duration of remission (PR or SD) was significantly longer for patients treated with ICI 182,780 compared to megestrol acetate (26 months and 14 months respectively, P = 0.04). These findings support further clinical comparison between ICI 182,780 and established endocrine agents.