Efficacy of high-dose toremifene therapy in postmenopausal patients with metastatic breast cancer resistant to aromatase inhibitors:a retrospective, single-institution study.

Abstract Aromatase inhibitors(AI)have established efficacy as first-line therapy in postmenopausal patients with hormone-sensitive metastatic breast cancer(MBC). However,the use of endocrine therapy has not yet been established for second-line and later therapy. Our study examined the efficacy of high-dose toremifene therapy(HD-TOR)in patients with MBC resistant to AIs. A retrospective analysis was carried out to determine outcomes in 85 postmenopausal patients with MBC resistant to AIs who began HD-TOR between May 2001 and October 2011. The patients received toremifene 120 mg once daily on consecutive days. The objective response rate(ORR)was 21.2%,the clinical benefit rate(CBR)was 41.2%,and the median time to treatment failure(TTF)was 7.3 months. The CBR was high in patients with ER-positive status(p=0.045),no visceral metastasis(p=0.037),HD -TOR as first- or second-line therapy(p=0.007),no history of tamoxifen(TAM)therapy(p=0.019),and no history of chemotherapy(p=0.017). Multivariate analysis showed that ER-positive status(p=0.005, odds ratio: 0.064)and no visceral metastasis(p=0.034, odds ratio: 0.323)were independent predictors of efficacy. The TTF was significantly longer in patients with ER-positive status(p=0.019)and no history of TAM therapy(p=0.015). Multivariate analysis showed that ER-positive status(p=0.025, hazard ratio: 0.377)and no history of TAM therapy(p=0.002, hazard ratio: 0.422)were independent predictors of efficacy. No patient discontinued HDTOR therapy due to adverse events. HD-TOR is an effective endocrine therapy for patients with MBC who have failed AIs.