Is Multifocal Regression a Risk Factor for Ipsilateral Breast Tumor Recurrence in the Modern Era After Neoadjuvant Chemotherapy and Breast Conservation Therapy?

Abstract

Purpose: Multifocal pattern of regression after neoadjuvant chemotherapy has been identified as a risk factor for ipsilateral breast tumor recurrence (IBTR). We aimed to determine the significance of multifocal regression as a predictor of IBTR after neoadjuvant chemotherapy and breast conservation therapy in the modern era. Methods and Materials: We retrospectively reviewed 346 patients treated between November 2009 and June 2017. Pattern of regression was categorized as pathologic complete response (pCR), unifocal (tumor present as a cohesive mass), limited multifocal (single cells or clusters of cells concentrated in 1 portion of the fibrotic area), or diffuse multifocal (cells spread over entire fibrotic area). IBTR was defined as new ipsilateral invasive or noninvasive breast tumor after breast conservation therapy. Predictive factors were analyzed using Cox regression. Results: Incidence of multifocal regression was 25.7% for the overall cohort and 12.2% for estrogen receptor (ER) negative/progesterone receptor (PR) negative/human epidermal growth factor receptor 2 (HER2) positive, 17.5% for triple-negative, 36.9% for ER+ or PR+/HER2-, and 38.5% for triple-positive (P