Assessment of Inter-observer Reproducibility of the Residual Cancer Burden Index and Neoadjuvant Chemotherapy Response in Breast Carcinoma

Background : Locally advanced breast cancers are nowadays treated with neoadjuvant chemotherapy (NAC) to downstage the tumor. One way to assess the NAC response is to use “Residual cancer burden index (RCB).” The aim of the study was to assess inter-pathologist reproducibility of residual cancer burden index and to evaluate different clinico-pathological parameters that determine the pathological response. Methods: In this retrospective cohort study, surgically excised specimens of 49 NAC treated breast cancer were examined by histopathology and immunohistochemistry over a period of one and half years. Four pathologists with different level of experience reviewed the reports (unaware of original RCB index) and slides and assigned the RCB indices for each case. Clinical, histopathological and immunohistochemical parameters were evaluated.. Fleiss- Kappa statistics was applied to assess interobserver reproducibility of RCB index. Results: No significant relationship was observed between RCB index (of original report) with age, largest tumor dimension and number of chemotherapy cycles . The RCB index of 49 cases as assigned by four pathologists was calculated by Fleiss-kappa statistics and it showed good overall agreement (82.6%). Conclusion: It has been observed that there is no significant relation between pathological response to NAC with age, largest tumor dimension and number of chemotherapy cycles of breast carcinoma. It can also be concluded that RCB can be reliably used to report neoadjuvant chemotherapy treated specimens of breast cancer.