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.