Survival outcomes following upfront surgery vs neoadjuvant chemotherapy for triple-negative and HER2-positive T1c and T2 breast cancer: A retrospective, population-based cohort study.

Abstract

e12592 Background: Neoadjuvant systemic therapy (NST) is the guideline-concordant approach for HER2-positive(+) and triple negative (TN) breast cancers over 2 cm in size. The decision between NST or upfront surgery for clinical T1cN0 HER2+ and TN breast cancers remains controversial. We compared the 10-year survival rates following NST vs upfront surgery for patients with hormone receptor (HR)-negative (HR-)/HER2+, HR+HER2+, and TN T1c-T2 tumors. Methods: We conducted a population-based, retrospective cohort study using administrative health databases at ICES. Data from all patients diagnosed with invasive breast cancer between 2009 and 2019 in Ontario, Canada were extracted from the Ontario Cancer Registry. Demographic, tumor, and treatment data were collected from the linked databases. Kaplan-Meier survival curves were generated to assess the 10-year survival rates for patients undergoing NST vs upfront surgery. Survival curves were compared using the log-rank test and stratified by receptor status, T stage, and nodal status. Statistical analysis was performed using SAS, with statistical significance set at P<0.05. Results: There were 395 HR-HER2+, 1199 HR+HER2+, and 1186 TN T1c tumors. There was no difference in 10-year survival between NST and upfront surgery for HR-HER2+ (P=.35) and HR+HER2+ (P=.46) T1c tumors. When stratified by T stage and nodal status, this finding was consistent across HR-HER2+ and HR+HER2+ T1c N0, N1, and N2 tumors. 10-year survival was greater for upfront surgery vs NST for overall TN T1c tumors (P<.001). This trend was significant for TN T1cN0 (P=.003) and T1cN1 (P=.001). Among T2 tumors, there were 827 HR-HER2+, 1945 HR+HER2+, and 2090 TN tumors. 10-year survival rates were similar for upfront surgery and NST for overall HR-HER2+ and HR+HER2+ T2 tumors (P=.68 and P=.64 respectively). However, upfront surgery showed higher 10-year survival for HR-HER2+ T2N2 (P<.001), as well as for overall TN T2 tumors (P<.001). This trend remained consistent across TN T2N1 and N2 (P<0.001 for both). Conclusions: There was no difference in 10-year survival between NST and upfront surgery for HER2-positive T1c tumors. The decision-making in this setting should therefore consider the potential for chemotherapy regimen de-escalation with upfront surgery versus the potential for NST to guide adjuvant therapies depending on response. We did observe better survival for TN T1c and T2 tumors having upfront surgery, which requires further study. Our cohort predates the CREATE-X trials, which underscores the need to study a more contemporary cohort with longer-term follow-up. Our findings may inform the decision-making for upfront surgery versus NST for patients with early-stage TN and HER2+ breast cancer.