Clinical outcomes of adjuvant taxane plus anthracycline versus taxane-based chemotherapy regimens in older adults with node-positive, triple-negative breast cancer: A SEER-Medicare study

Background: Triple-negative breast cancer (TNBC) is a subtype of breast cancer associated with an aggressive clinical course. Adjuvant chemotherapy reduces the risk of recurrence and improves survival in patients with node-positive TNBC. The benefit of anthra-cycline plus taxane (ATAX) regimens compared with non-anthracycline-containing, taxane-based regimens (TAX) in older women with node-positive TNBC is not well characterised. Methods: Using the Surveillance, Epidemiology, and End Results-Medicare database, we identified 1106 women with node-positive TNBC diagnosed at age 66 years and older between 2010 and 2015. We compared patient clinical characteristics according to adjuvant chemo-therapy regimen (chemotherapy versus no chemotherapy and ATAX versus TAX). Logistic regression was performed to estimate the odds ratios (OR) and 95% confidence intervals (CIs). Kaplan-Meier survival curves were generated to estimate 3-year overall survival (OS) and cancer-specific survival (CSS). Cox proportional hazard models were used to analyse OS and CSS while controlling for patient and tumour characteristics. Results: Of the 1106 patients in our cohort, 767 (69.3%) received adjuvant chemotherapy with ATAX (364/767, 47.5% ), TAX (297/767, 39%) or other regimens (106/767, 13.8%). Independent predictors of which patients were more likely to receive ATAX versus TAX included more extensive nodal involvement (>4), age, marital/partner status and non -cardiac comorbidities. There was a statistically significant improvement in 3-year CSS (81.8% versus 71.4%) and OS (70.7% versus 51.3%) with the use of any chemotherapy in our cohort (P < 0.01). Three-year CSS and OS for patients who received ATAX versus TAX were similar at 82.8% versus 83.7% (P = 0.80) and 74.2% versus 72.7% (P = 0.79), respectively. There was a trend towards improved CSS and OS in patients with four or more positive lymph nodes who received ATAX versus TAX (hazard ratio 0.66, 95% CI: 0.36-1.23, P = 0.19 and hazard ratio 0.68, 95% CI: 0.41-1.14, P = 0.14, respectively). Conclusion: Among older women with node-positive TNBC, a majority of patients received adjuvant chemotherapy, which was associated with an improvement in CSS and OS. When compared with TAX chemotherapy, there was a trend towards better outcomes with ATAX for patients with >4 nodes. Published by Elsevier Ltd.