Abstract
There are currently no established second- and later-line therapies for postmenopausal women with hormone receptor-positive advanced or metastatic breast cancer. We examined the efficacy of high-dose toremifene (HD-TOR) for this patient group and whether aromatase inhibitor (AI) resistance influences HD-TOR treatment outcome. This retrospective analysis investigated the outcomes of 19 women with postmenopausal hormone-sensitive recurrent or metastatic breast cancer who received HD-TOR, defined as 120 mg daily from 2012 to 2016. The median follow-up duration was 9.67 months. The overall response rate (ORR) and clinical benefit rate (CBR) were compared between various clinical subgroups, including patients exhibiting primary or secondary AI resistance as defined by the timing of recurrence or progression. Time to treatment failure (TTF) was estimated by the Kaplan–Meier method and compared between subgroups by the log-rank test. The overall ORR was 21.1%, and the CBR was 31.6%. CBR was significantly higher for patients without liver metastasis (50% vs. 0%, p = 0.044). Nine cases exhibited primary and eight cases secondary AI resistance. Both ORR and CBR were higher in patients with secondary AI resistance (25% vs. 0%, p = 0.087; 38% vs. 11%, p = 0.29). The median TTF was 6.2 months in the entire AI-resistant group (n = 17) and was longer in the secondary resistance subgroup than in the primary resistance subgroup (8.40 vs. 4.87 months; log-rank: p = 0.159). High-dose TOR appears to be most effective for postmenopausal breast cancer cases with secondary resistance to AIs, cases without prior AI treatment, and cases without liver metastasis. The detailed mechanisms of AI resistance and the clinical features of responsive cases need to be further clarified to identify the best candidates for HD-TOR.
Highlights
Aromatase inhibitors (AIs) have long been the primary firstline endocrine treatment for postmenopausal women with hormone receptor-positive metastatic or locally advanced breast cancer [1, 2]
Clinicians have several options for the second- and later-line endocrine therapy, such as fulvestrant, AIs not used as first-line therapy, and AIs combined with CDK 4/6 inhibitors or mechanistic target of rapamycin
One aim of the present study is to examine the effectiveness of high-dose toremifene (HD-TOR) against postmenopausal hormone-sensitive progressive or recurrent breast cancer
Summary
Aromatase inhibitors (AIs) have long been the primary firstline endocrine treatment for postmenopausal women with hormone receptor-positive metastatic or locally advanced breast cancer [1, 2]. Several prospective trials have reported that a combination of CDK 4/6 inhibitors and AIs has better efficacy as first-line endocrine therapy than AIs alone [3,4,5]. There are no firmly established second- and later-line endocrine therapies for postmenopausal women with hormone receptor-positive metastatic breast cancer. The cost-effectiveness of these new endocrine and targeted therapies is still debated given their relatively high cost and lack of definitive evidence for superior efficacy [9, 10]. An endocrine therapy with equivalent efficacy at a lower cost is desirable
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