Measurement of Residual Cancer Burden in Breast Cancer Patients Treated with Neoadjuvant Chemotherapy and Correlation with Biomarker Expression and Molecular Subtypes.
Amber Cockburn, Yan Peng, David Euhus, Barbara Haley, Venetia Sarode. University of Texas Southwestern, Dallas
Background: The assessment of tumor response to neoadjuvant chemotherapy (NAC) is important for prognostication of patients with breast cancer. The residual cancer burden (RCB) can be quantified using the UT MD Anderson RCB calculator index. This study aims to correlate tumor biomarker expression and clinicopathologic parameters with RCB status in patients with locally advanced breast cancer treated with NAC.
Design: Two hundred and three patients with locally advanced breast cancer were treated with NAC at our institution between the years 2000-2009. Pathology slides and reports from 156 patients who completed NAC and definitive surgery were reviewed retrospectively. Tumor cellularity percent, tumor bed size, DCIS component, number of positive lymph nodes and size of the largest metastatic focus were assessed. The RCB class was assigned using the RCB index (www.mdanderson.org/breastcancer_RCB). Pathologic complete response (pCR), RCB I, RCB II and RCB III correspond to pCR, minimal, moderate and extensive residual disease respectively. Results of biomarker expression (ER, PR, HER2, Ki67, and p53) and DNA ploidy performed on core biopsies were analyzed and correlated with RCB. Tumors were classified into the luminal A, luminal B, HER2 and triple negative molecular groups using immunohistochemistry.
Results: The median age was 46 years. Thirty-eight cases exhibited pCR; 5 RCB I; 56 RCB II; and 58 RCB III. The mean RCB score for RCB I, RCB II and RCB III was 0.13, 2.28, and 4.16, respectively. Race, age, tumor grade, PR expression and DNA ploidy showed no significant correlation with RCB class. Clinical stage (p <0.05), high Ki67, p53 overexpression, ER and HER2 expression showed significant difference between the RCB classes.
|pCR/RCB I||RCB II-III||P Value|