Neoadjuvant Versus Adjuvant Therapy for Metaplastic Breast Cancer: Insights from the National Cancer Database-Is There a Winning Strategy?

Abstract

This study analyzed a large national cohort to compare treatment strategies and survival outcomes in metaplastic breast cancer (MtBC), a rare and aggressive subtype with poor treatment response. Adult female patients with MtBC diagnosed between 2006 and 2021 were identified from the National Cancer Database and grouped by chemotherapy sequence (neoadjuvant vs. adjuvant) to evaluate clinical characteristics and survival outcomes. Among 9526 patients, 30.1% received neoadjuvant and 69.9% adjuvant chemotherapy. The cohort was predominantly white (76.7%) and non-Hispanic (90.8%), with a median age of 60 years; most had a comorbidity score of 0 (81%). Neoadjuvant therapy use increased from 14.3 to 43.9% and was more common among younger patients with advanced clinical stages. The immunotherapy administration grew from 0 to 23.95%. Over a mean follow-up of 69 months, 5-year overall survival was higher in the adjuvant group (80.7% vs. 66.7%). In multivariable analysis, adjuvant therapy was associated with improved overall survival [hazard ratio (HR) 0.65; 95% CI 0.54-0.72; p < 0.001]. Mastectomy, radiation, and higher income level were also linked to improved outcomes, while older age, nodal involvement, comorbidities, and lymphovascular invasion were associated with higher mortality. Adjuvant chemotherapy and aggressive local treatments were associated with improved survival, supporting a tailored approach that includes upfront surgery followed by adjuvant therapy as a potentially optimal strategy for operable cases. Meanwhile, the increasing use of neoadjuvant chemotherapy has coincided with rising survival rates, and the integration of immunotherapy into neoadjuvant regimens is also promising, highlighting the need for future studies.