Neoadjuvant Chemotherapy Use in Breast Cancer is Greatest in Excellent Responders: Triple-Negative and HER2+ Subtypes.

Background: While breast cancer has historically been treated with surgery followed by adjuvant chemotherapy (AC) and radiation when indicated, neoadjuvant chemotherapy (NAC) use is thought to be increasing; however, the trends of its use in various biological subtypes have not been evaluated. We sought to evaluate the trend of NAC use over time by biological subtype.
Methods: We identified all patients with invasive breast cancer who underwent curative intent surgery and were treated with chemotherapy from 2010 to 2015 from the National Cancer Database. An unadjusted analysis of trends in proportions over time was performed using Cochran-Armitage trend tests stratified by hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status.
Results: Of 315,264 patients who received chemotherapy, 251,726 (79.8%) received AC and 63,538 (20.2%) received NAC. From 2010 to 2015, significant increases in NAC use were seen in all biologic subtypes (all p < 0.001). The highest proportions and greatest increases in proportions of NAC were seen among triple-negative breast cancers (TNBC; 19.5-33.7%) and HER2+ (HR-/HER2+, 21.5-39.8%; HR+/HER2+, 17.0-33.7%) tumors. HR+/HER2- tumors also had a statistically significant increase in use but this increase was less dramatic (13.0-16.8%) and NAC use in recent years was significantly lower than in other subtypes (p < 0.001).
Conclusion: Within patients receiving chemotherapy for breast cancer, its receipt in the neoadjuvant setting has been increasing among all biologic subtypes. The highest use of NAC is in TNBC and HER2+ disease, with use in these subgroups being twice as frequent as in HR+/HER2- disease.