Abstract P1-14-13: Residual proliferative cancer burden (RPCB) is superior to RCB index as prognostic tool in early breast cancer patients (EBC) treated with neoadjuvant chemotherapy (NAC)
Authors: Pons V , Pérez-Fidalgo JA , Burgués O , Martín P , Cejalvo JM , Bermejo B , LLuch A 
Published: May 2016

BACKGROUND: Many different scales have been developed in order to assess response to NAC. Apart from Miller and Payne and RCB systems, recently the addiction of post-NAC pathological Ki 67 (yp Ki67) to RCB, called RPCB system, has been considered as a more accurate prognostic tool. The aim of this study is to assess the prognosis value of RPCB in a routine practice cohort and to compare it to RCB index and ypKi67.

METHODS: We performed a retrospective analysis of our database. Patients with stage I-III considered candidate for NAC from July 2008 and August 2011 were included. RPCB and RCB were calculated as previously published. Hormone receptor expression (HR), ypKi 67 and Her2 were assessed following international guidelines. The Harell c-index were used to compare the prognostic value of RPCB, RCB and ypKi 67. Clinical, therapeutic and pathological data were obtained from medical records. A correlation with disease-free survival (DFS) and overall survival (OS) was done using the Kaplan-Meier method and Cox regression model.

RESULTS: From our database including 333 EBC patients treated with NAC 184 had data to calculate RPCB, RCB and ypKi 67, of whom 51.6% were HR+Her2- tumours, 21.7% HR+Her2+, 8.2% HR- Her2+ and 18.5% triple negative. Mean tumour size was 37.5 mm (25-45). The majority of the patients had histhological grade II-III tumours (84.2%) and N stage 0-1 (96.7%). 67.4% of the patients received anthracycline and taxane-based NAC, associated to trastuzumab in Her2+ patients (26.1%). Pathological complete response by subtypes were 6.3%, 17.5%, 60% and 26.5%, respectively. With a median follow-up of 49.9 months, DFS and OS at 36 months were 85.2% and 95.1%. In the multivariate analysis all three systems were prognostic for DFS (RPCB p&lt;0.001; RCB p=0.001; ypKi 67 p= 0.002) and OS (RPCB p&lt;0.001; RCB p=0.011; ypKi 67 p= 0.037). Comparison of Harell c-index for DFS between RCPB and RCB showed a trend of RPCB towards a more accurate prognostic power (0.89 vs 0.81, p=0.061) that was significant when comparing RCPB vs ypKi67 and RPCB vs ypKi67 (0.89 vs 0.77, p=0.010). However no statistically differences were found in terms of OS (RPCB vs RCB 0.85 vs 0.82, p=0.357 and RPCB vs ypKi67 0.85 vs 0.72, p= 0.088).

CONCLUSION: RPCB, RCB and ypKi67 are prognostic for both DFS and OS in EBC patients treated with NAC. RPCB is a more accurate prognostic tool than ypKi67 and showed a trend towards superiority compared to RCB.

Citation Format: Pons V, Pérez-Fidalgo JA, Burgués O, Martín P, Cejalvo JM, Bermejo B, LLuch A. Residual proliferative cancer burden (RPCB) is superior to RCB index as prognostic tool in early breast cancer patients (EBC) treated with neoadjuvant chemotherapy (NAC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-14-13.