Dosimetric plan evaluation of hypofractionated 3-dimensional conformal radiotherapy (3DCRT) and 2-dimensional (2D) simulator planning in whole breast irradiation after breast conserving surgery

Abstract

Background: Pathologic complete response (pCR) is known to be a predictive marker for favorable outcome after neoadjuvant treatment in HER2 positive (þ) breast cancer. Our aim was to investigate the association between hormone receptor (HR) or tumorinfiltrating lymphocytes (TILs) and pCR in HER2 (þ) breast cancer treated with dual anti-HER2 therapy. Methods: Ninety-four patients with HER2 (þ) breast cancer who received neoadjuvant treatment with docetaxel, carboplatin, trastuzumab and pertuzumab (TCHP) were included in this retrospective analysis. Associations between TILs and pCR were assessed in the overall and hormone receptor (HR) positive (þ) and HR negative (-) populations. We classified subgroups with a cutoff value of stromal TILs (20% TILs vs > 20% TILs) based on ROC curves. Results: Of the 94 cases, 54 (57.4%) tumors achieved pCR (ypT0/is N0) and median TILs was 17.07% [13.81-20.65]. In analysis of hormone receptor, pCR was 51.0% (n ¼ 26/51) in HR (þ) group and 65.1% (n ¼ 28/43) in HR (-) group (p ¼ 0.167). The pCR rate was higher in the high TILs group than in the low TILs group (74.1% vs 51.4%, p ¼ 0.038). In HR (-) group, high TILs and low TILs achieved 90% (n ¼ 9/10) and 57.6% (n ¼ 19/33) of pCR, respectively. In HR (þ), pCR rates of high TILs and low TILs subgroups were 64.7% (n ¼ 11/17) and 41.7% (n ¼ 15/34). Conclusions: In HER2 (þ) breast cancer, HR (-) and high TILs showed higher pCR compared with HR(þ) and low TILs. TILs might be a predictive marker for the treatment response to neoadjuvant dual anti HER2 based chemotherapy. Further investigation in a larger cohort of samples is needed to validate these results. Legal entity responsible for the study: Asan Medical Center. Funding: Has not received any funding.