[129] 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.

Tumor Biomarkers Correlated with RCB Classification
 pCR/RCB IRCB II-IIIP Value
Ki67   
4410.001
>30%3873 
p53   
16670.01
>10%2641 
ER   
Negative28490.02
Positive1565 
PR   
Negative32690.14
Positive1145 
HER2   
Nonamplified20830.003
Amplified2331 


HER2 and triple negative subtypes were more frequently associated with pCR/RCB I than luminal subtypes (p=0.002).
Conclusions: RCB can be evaluated retrospectively from routine pathology material using the MD Anderson RCB calculator index to more accurately classify tumor response to neoadjuvant chemotherapy.
Category: Breast

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 41, Monday Morning

 

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