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 anthracycline 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 chemotherapy 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.