Abstract P5-14-02: Triple negative breast cancer - Adjuvant chemotherapy use and survival outcomes in Stage IA disease

Background: The potential benefit of adjuvant chemotherapy in patients with Stage IA triple negative breast cancer (TNBC) has not been defined. In general, patients with T1a and T1b lesions have not been included in adjuvant chemotherapy trials and the inclusion of T1c tumors has been limited. In this study using National Cancer Data Base (NCDB) we investigated the actual use of adjuvant chemotherapy in Stage IA TNBC patients relative to tumor size (T1a, T1b, T1c) and report their survival outcomes. Patients and Methods: Using NCDB we evaluated a cohort of 13,065 women with TNBC diagnosed between 2010-2012 who had American Joint Committee on Cancer Stage IA (node-negative with pathological T1a, T1b or T1c) tumors. Overall survival (OS) was the primary outcome variable. Based on the tumor size, patients were stratified on receipt of adjuvant chemotherapy or not. Patients were also stratified according to receipt of adjuvant radiation, radiation with boost, or none. Other adjusted variables included: age, race, Charlson comorbidity index, payer status, income, education, distance traveled, treating facility, and treatment delays. Multivariate Cox regression was employed to analyze the effect of adjuvant chemotherapy on overall survival. Results: The mean patient age for the entire cohort was 59.2 years (range 22-90 years), 55.8 years for the chemotherapy group, and 67.8 years for the non-chemotherapy group. There were 1275 T1a, 3197 T1b, and 7729 T1c patients. Tumor size was a very strong predictor of survival. Compared to T1a tumors, HR for death was 1.43 (95% CI: 0.86 –2.37) for T1b tumors and 3.00 (95% CI: 1.86 – 4.83) for T1c tumors. Out of all T1a, T1b, and T1c tumors in this cohort, 48.1 %, 72.6%, and 89.3% of patients received adjuvant chemotherapy respectively. A hazard ratio (HR) of death was 0.42 (95% CI: 0.31 – 0.57) for all patients who received chemotherapy compared to non-chemotherapy group. 4-year OS by tumor size and chemotherapy usage is listed in the table indicating an absolute increase of OS with adjuvant chemotherapy employment. HR for death was 0.90 (CI: 0.62 – 1.31) with use of radiation only and 0.67 (95% CI: 0.53 – 0.85) with use of radiation with boost when compared to no radiation therapy. Conclusion: NCDB indicated that the majority of patients with Stage IA TNBC received adjuvant chemotherapy, including 48% of patients with T1a lesions. Our data analysis demonstrated a statistically significant 4-year OS benefit in patients with T1b and T1c tumors who received adjuvant chemotherapy compared to those who did not. The survival benefit of adjuvant chemotherapy in patients with T1a tumors, however, did not reach statistical significance. Prospective randomized trials could define the potential benefits of adjuvant chemotherapy in patients with Stage IA TNBC, particularly for those with T1a and T1b tumors. Citation Format: Patel AN, Shi R, Peddi P, Burton GV. Triple negative breast cancer - Adjuvant chemotherapy use and survival outcomes in Stage IA disease [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-14-02.