FORMESTANE VERSUS MEGESTROL-ACETATE IN POSTMENOPAUSAL BREAST-CANCER PATIENTS AFTER FAILURE OF TAMOXIFEN - A PHASE-III PROSPECTIVE RANDOMIZED CROSS-OVER TRIAL OF 2ND-LINE HORMONAL TREATMENT (SAKK-20 90)/

The aim of the study was to compare efficacy and tolerability of the n ew aromatase inhibitor formestane (Lentaron(R)) with megestrol acetate (Megestat(R)) (MGA) in postmenopausal patients with advanced breast c ancer. 179 patients were randomised to receive either 250 mg formestan e intramuscularly biweekly or MGA 160 mg orally daily. 51% of the pati ents had received tamoxifen as adjuvant treatment; 73% of the patients had positive and 16% unknown oestrogen receptor values. The response rate was 17% in both treatment arms (95% confidence interval 10-26% fo r formestane and 10-27% for MGA). Disease stabilisation greater than o r equal to 6 months was seen in 25% of the formestane and 22% of the M GA patients. Time to treament failure was 120 days in the formestane a rm and 111 days in the MGA arm. There was no significant difference be tween the treatments with regard to response rate and time to treatmen t failure. Overall toxicity was similar in both arms, but weight gain >3 kg (P = 0.081) and severe cardiovascular toxicity (P = 0.044) were more frequently observed with MGA, e.g. deep vein thrombosis 0/90 form estane versus 5/81 MGA cases (P = 0.022). Formestane was associated wi th worsening of hot flushes/sleeping problems (P = 0.051) and mild leu copenia (P = 0.004). In our study, formestane and MGA showed similar a ntineoplastic activity as second-line hormonal treatment for advanced breast cancer. Both drugs have a specific toxicity profile. MGA was as sociated with significantly more severe cardiovascular toxicity and we ight increase than formestane. (C) 1997 Published by Elsevier Science Ltd.