Nsabp B-41, A Randomized Neoadjuvant Trial: Genes And Signatures Associated With Pathologic Complete Response (Pcr).

511 Background: NSABP B-41 randomly assigned 529 patients (pts) with HER2 positive breast cancer to neoadjuvant trastuzumab (T), lapatinib (L), or combination (T+L), with weekly paclitaxel following doxorubicin and cyclophosphamide. No significant differences in pCR were found, but overall survival was significantly increased for pCR. Methods: RNA was extracted from FFPE tumor specimens, run on the NanoString Breast Cancer 360 Plus panel. Gene counts were normalized to include housekeeping genes, 33 biological signatures from 776 genes across 23 pathways and transformed into logarithm scale with base two. Univariate logistic regression was used to screen candidate genes and signatures that are prognostic of pCR, with false discovery rate controlled at 0.1. Multivariable logistic regression with lasso regularization was used for model selection. Results: 194 core biopsy samples were available; 69 treated with T, 64 with L and 61 with T+L. 20 prognostic genes are selected for trastuzumab-based regimens (TBR), including the epithelial-mesenchymal transition (HEMK1, GRB7, ERBB2, TMPRSS4), adhesion and migration (ITGB6, COL27A1, NRCAM), JAK-STAT (SOCS2), Hedgehog (LRP2), ER signaling (ELOVL2, MAPT), DNA damage and repair (NPEPPS, PRKDC), MAPK (DUSP6, PRKCB), Apoptosis (BCL2), proliferation (TFDP1). ERBB2 expression are associated with pCR in patients on TBR (OR = 1.73), but not for patients on L (interaction p = 0.01). HER2-Enriched correlation (p < 0.001), ESR1 (OR = 0.78, 95% CI = 0.69-0.88, p < 0.001), PD1 (OR = 1.68, 95% CI = 1.12-2.52, p = 0.01) and Tumor Inflammation Score (OR = 1.58, 95% CI = 1.18-2.11, p = 0.002) are associated with pCR in TBR. No genes or signatures were found to be predictive of treatment benefit from L added to T. Conclusions: BC360 highlighted tumor progression and signaling genes prognostic for TBR. HER2-Enriched correlation, ERBB2 and PD1 expression, and immune activation signatures were associated with pCR in TBR and may provide personalized treatment guidance.