Adjuvant treatment for triple negative breast cancer with residual tumor after neo-adjuvant chemotherapy. A single institutional retrospective analysis

Purpose: Incomplete response to neoadjuvant chemotherapy (NACT) in triple negative breast cancer (TNBC) patients is correlated to high risk of relapse. This study aimed to evaluate the role of adjuvant chemotherapy in TNBC with residual tumor after NACT. Methods: We retrospectively reviewed the outcome of patients with TNBC with residual tumor at surgery after a neoadjuvant treatment, followed by either adjuvant chemotherapy or observation. Primary endpoints were Disease Free Survival (DFS) and Overall Survival (OS). Results: Between January 2000 and December 2016, 223 patients with early TNBC operated at the European Institute of Oncology were eligible. A total of 83.4 % of patients received adjuvant chemotherapy after surgery. 90 patients received standard dose infusional regimens, while 96 patients (51.6 %) received oral metronomic chemotherapy. Adjusting the analysis by surgical stage and Ki67 value there was a benefit for DFS and OS in favor of the group that received postoperative chemotherapy (DFS-HR 0.58 p = 0.04; OS-HR 0.54, p = 0.02). At a subgroup analysis according to the different adjuvant treatments received, a benefit for metronomic chemotherapy versus no chemotherapy both for DFS (HR 0.46, p = 0.008) and OS (HR 0.45, p = 0.009) was reported. Conclusion: Our retrospective analysis in a large cohort of TNBC patients with residual disease after NACT confirms the benefit of adding a postoperative treatment to reduce risk of relapse and death. Based on these results, we suggest that the adjuvant therapy based on metronomic cyclophosphamide and methotrexate deserves further investigation in this patients population.