Abstract 203P
Background
There are different published systems to score the pathological response after neoadjuvant chemotherapy (NACT) in breast cancer and there is a great variability in their interpretation, application and meaning. Among these grading methods stand out two classifications: Miller and Payne (MP) and Residual Cancer Burden (RCB). The objective of the study was to validate and compare both classifications in our series of patients.
Methods
A retrospective analysis was performed among breast cancer patients treated with NACT in a single institution in which RCB and MP grading system were both systematically used. Results obtained for each assessment system were assessed in terms of distant disease-free survival (DDFS) by Kaplan-Meier method, and compared with the log-rank test. Cox regression analysis was performed to assess the association of both systems with DDFS.
Results
MP and RCB were assessed in 289 breast cancer tumours after NACT from 2007 to 2018. Median follow-up was 43.2 months. Both methods grading were able to discriminate different DDFS (RCB, χ2= 55.147, p<0.001) (MP, χ2= 32.405, p<0.001). Results were also significant in triple negative (RCB, χ2= 34.803, p<0.001) (MP, χ2= 22.125 , p<0.001), HER2+ (RCB, χ2= 68.485, p<0.001) (MP, χ2= 28.371 , p<0.001) and luminal HER2 negative tumours (RCB, χ2= 8.795, p=0.032) (MP, χ2= 15.197 , p=0.004). When cox regression analyse was performed only RCB retained significant results for the whole population (HR 2.07, 95% confidence interval [CI] 1.31-3.25, p=0.002). RCB also retained significance in triple negative (HR 4.73, 95% [CI] 1.57-14.29, p=0.006) and HER2+ (HR 4.03, 95% [CI] 1.49-10.89, p=0.006). For luminal HER2 negative neither of the two classifications maintain significant results in the multivariate analysis.
Conclusions
In our study, RCB and MP were both predictive for survival in univariate analysis. When we compare the two classification only RCB retain significance. We conclude RCB is an excellent tool for predict survival in this population, especially for triple negative and HER2+ patients. Efforts are needed to find a classification that best suits luminal HER2 negative tumours.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.