Use and Benefit of Neoadjuvant Versus Adjuvant Chemotherapy in Node-Negative, T1 Triple Negative Breast Cancer.

Purpose: There are scarce data about the use and benefit of neoadjuvant chemotherapy (NACT) in small size, node-negative triple-negative breast cancer (TNBC). We examined pathological response and survival outcomes of patients with T1N0 TNBC who received NACT.

Methods: This is a retrospective cohort study using data from the Surveillance, Epidemiology, and End Results database of patients with T1N0 TNBC diagnosed between 2010 and 2020. Cox regression models were used to compare overall survival (OS) for adjuvant chemotherapy (ACT) and NACT cohorts. Cumulative incidence functions and breast cancer-specific hazard models were used to compare breast cancer specific survival (BCSS) between ACT and NACT cohorts.

Results: We found 8146 patients treated with ACT and 1263 patients treated with NACT. Age < 50 years, mastectomy and radiation therapy were associated with higher odds of receiving NACT. There was no difference in BCSS or OS for patients with T1b/T1cN0 TNBC who received NACT or ACT. However, patients with T1aN0 TNBC had worse BCSS and OS when treated with NACT as compared to those who received ACT. Pathological complete response (pCR) in T1N0 tumors was associated with improved OS (HR, 0.28) and BCSS (HR, 0.21). Furthermore, T1aN0 tumors had lower pCR rate than T1cN0 tumors (18% vs. 47%).

Conclusion: Patients with node-negative, T1b and T1c tumors benefit equally from the use of ACT and NACT. The results of worse outcome in patients with node-negative, T1a tumors treated with NACT compared to ACT are intriguing and need further investigation.