The choice of a neoadjuvant chemotherapy cycle for breast cancer has significance in clinical practice: results from a population-based, real world study

Objective: Neoadjuvant chemotherapy (NAC) is currently used in both early stage and locally advanced breast cancers. The survival benefits of standard vs. non-standard NAC cycles are still unclear. This study aimed to investigate the relationship between NAC cycles and survival based on real world data. Methods: We identified patients diagnosed with invasive primary breast cancers who underwent NAC followed by surgery. Patients who received at least 4 NAC cycles were defined as having received standard cycles, while patients who received less than 4 NAC cycles were defined as having received non-standard cycles. Kaplan-Meier curves and Cox proportional hazard models were used to estimate the disease-free survival (DFS) and overall survival (OS). Results: Of the 1,024 included patients, 700 patients received standard NAC cycles and 324 patients received non-standard NAC cycles. The DFS estimates were 87.1% and 81.0% (P = 0.007) and the OS estimates were 90.0% and 82.6% (P = 0.001) in the standard and non-standard groups, respectively. Using multivariate analyses, patients treated with standard NAC cycles showed significant survival benefits in both DFS [hazard ratio (HR): 0.62, 95% confidence interval (CI): 0.44 0.88] and OS (HR: 0.54, 95% CI: 0.37-0.79). Using stratified analyses, standard NAC cycles were associated with improved DFS (HR: 0.59, 95% CI: 0.36-0.96) and OS (HR: 0.49, 95% CI: 0.28-0.86) in the HER2 positive group. Similar DFS (HR: 0.50, 95% CI: 0.25-0.98) and OS (HR: 0.45, 95% CI: 0.22-0.91) benefits were shown for the triple negative group. Conclusions: Standard NAC cycles were associated with a significant survival benefit, especially in patients with HER2 positive or triple negative breast cancer.