Long-term survival in elderly women receiving chemotherapy for non-metastatic breast cancer: a population-based analysis

Background Older women are poorly represented in trials evaluating chemotherapy for breast cancer (BC). This study aimed to describe survival and associated factors among elderly women receiving chemotherapy for non-metastatic BC. Methods This was a population-based cohort study including women ≥ 70 years old diagnosed with invasive, non-metastatic BC from 2010 to 2017 in SEER. Among those who received chemotherapy, overall survival (OS) was determined using Kaplan–Meier curves and hazard ratios were reported with 95% confidence intervals (CIs). Adjustment was made for available confounders. Co-morbidity is not available in SEER. BC-specific survival (BCSS) and subdistribution hazard ratios were determined using competing risks analysis. Results The cohort consisted of 109,239 women aged 70+, of whom 17,961 (16%) received chemotherapy. Chemotherapy patients were younger (median 73.0 years vs. 77.0), had more advanced disease (25% stage III vs. 5.2%), and were more likely to receive mastectomy (50% vs. 33%). Among chemotherapy patients, 5-year OS was 77.8% (95% CI 76.9–78.6%), and for women 80+ was 60.2% (95% CI 57.5–63.1%). More recent diagnoses, no previous history of cancer, and receipt of radiotherapy were all associated with improved BCSS. Conversely, older age, higher tumour grade, advanced stage, and human epidermal growth factors receptor (HER)2 negative tumours were associated with worse BCSS. 56% of deaths were due to BC, and women aged 80+ had worse BCSS compared to those aged 70–79 (adjusted sdHR 1.62, 95% CI 1.43–1.84). Conclusions Elderly women with advanced disease can achieve good survival after chemotherapy for non-metastatic BC. Those with HER2+ disease have superior survival, reinforcing benefit in this population.