P16-3 Maintenance therapy in HER2 and hormone receptor-positive breast cancer

Abstract

After the standard first-line treatment for HER2 and hormone receptor-positive breast cancer, maintenance therapies are still controversial. Here, we report the real-world data of trastuzumab plus endocrine therapy compared with trastuzumab plus chemotherapy in HER2 and hormone receptor-positive metastatic breast cancer. This retrospective, multicenter, observational cohort study enrolled women aged 18 years or older with measurable or evaluable HER2 and hormone receptor-positive metastatic breast cancer who received chemotherapy and trastuzumab as first-line treatment between January 2009 and October 2019. We evaluated the efficacy and safety of trastuzumab plus endocrine therapy and trastuzumab plus chemotherapy. 102 patients were selected: 67 (65.7%) patients received trastuzumab plus endocrine therapy including aromatase inhibitors, fulvestrant, tamoxifen, or toremifene. While 35 (34.3%) patients received trastuzumab plus chemotherapy including capecitabine or vinorelbine as maintenance therapy. Maintenance endocrine therapy significantly improved progression-free survival (PFS) compared with chemotherapy (median progression-free survival 10.6 months [95% CI 8.609-12.658] vs 6.7 months [5.276-8.058], respectively; adjusted hazard ratio [HR] 0.648 [95% CI 0.428-0.981], p=0.040). The median PFS in patients without brain metastasis was 10.8 months (95% CI 9.380-12.154) in the endocrine therapy group versus 6.7 months (5.202-8.132) in the chemotherapy group (HR 0.485 [95% CI 0.303-0.777]), p=0.003). The most common adverse event was arthralgia (8,12%) in the endocrine therapy group, while hand-foot syndrome (25,71%) occurred in the chemotherapy group. Maintenance endocrine therapy could improve the survival of HER2 and hormone receptor-positive metastatic breast cancer patients.