Evaluation of Pathological Response in Post-Neoadjuvant Chemotherapy Breast Carcinoma Specimens using Residual Cancer Burden System

Abstract

Introduction: Many systems have been proposed to classify the degree of tumour response to therapy in post-neoadjuvant Chemotherapy (NACT) breast cancers. The Residual Cancer Burden (RCB) developed by MD Anderson cancer hospital is an online tool for the quantification of residual disease that is easy to practice, reproducible, and the RCB score has been clinically validated as independent prognostic factor for long-term survival. Aim: To evaluate the methodology for grossing and microscopic examination for assessing pathologic response in postNACT breast cancer specimens using RCB system developed by MD Anderson cancer institute and its feasibility for routine practice. Materials and Methods: The present cross-sectional study was conducted in Basavatarakam Indo American Cancer Hospital and Research Institute Hyderabad over a duration of three months from May 2018 to July 2018. Histologically proven breast carcinoma patients who were treated with both NACT and surgery were included in the study. Before surgery, these patients were treated with either anthracycline-based chemotherapy regimen with or without additional taxanes or targeted therapy with transtuzumab. RCB score and class were calculated to assess pathologic response to NACT. Analysis was performed individually by two senior pathologists, who has expertise in breast pathology and a junior pathologist. Consensus opinion was noted in case of discrepancies. Results: The study included 50 carcinoma breast specimens. All the cases werefemales. 49 cases were diagnosed as invasive carcinoma, No Special Type (NST) and one was lobular carcinoma. pCR (Pathological complete response) was seen in 9 (18%) and residual disease was seen in 41 (82%) patients. Conclusion: The present study highlights feasibility of application of RCB system in assessing pathological response following NACT in breast cancer. Incorporating RCB score and class in the reporting helps the surgical pathologist to overcome sampling errors caused by heterogeneously variable cellularity commonly encountered in these type of specimens.