Association of tumor-infiltrating lymphocytes (TILs) and immune signatures with PAM50 intrinsic subtyping hormone receptor-positive (HR+)/HER2-negative (HER2-) early breast cancer (BC): A translational analysis of two multicentric neoadjuvant trials.

Abstract

558 Background: HR+/HER2− BCs are generally described as immunologically cold, with low levels of TILs and PD-L1. Nevertheless, the addition of immunotherapy (ICI) to chemo has been reported to increase pCR rates in high-risk early HR+/HER2– BCs. Assessing the interaction between immune features and tumor biology may identify of a subset of patients (pts) with HR+/HER2− BC that would be the ideal candidates for the combination of chemo and ICI. Methods: Gene-expression data from two multicentric neoadjuvant phase II trials (GIADA, LETLOB) enrolling stage II-IIIA HR+HER2- BC pts was retrieved (Dieci, CCR 2022; Guarneri, JCO 2014). In the GIADA trial, 758 genes were assessed on baseline tumor samples by nCounter (N=43). In the LETLOB trial, gene-expression data (Affymetrix platform) from baseline core-biopsies was available for 66 pts. Intrinsic subtype was assigned using a research-based PAM50 predictor. TILs were evaluated following guidelines. Association of TILs and immune signatures with intrinsic subtyping was assessed by Kruskal-Wallis test. Results: PAM50 subtype distribution (N=109) was 44% Luminal B (LumB), 33% Luminal A (LumA), 18% Basal-like, 5% HER2-enriched (HER2-E). TILs were assessed on 101 samples: median 2 (range 0-100). Basal-like BCs showed higher TILs than other subtypes (p=0.008). No significant difference was observed between LumA and LumB BCs (Table). Basal-like tumors showed higher levels of previously published immune signatures associated with CD8 T-cells (p<0.001), Cytotoxic cells (p<0.001), IFN-gamma (p<0.001), and response to ICI in the GeparNuevo trial (p=0.003) (N=109). PD-1 (p=0.002), PD-L1 (p=0.001), and PD-L2 (p=0.001) genes were also more expressed in Basal-like BCs (evaluable in 43 samples). No significant difference was observed between LumA and LumB tumors. A significant weak to moderate positive correlation was observed between continuous TILs and immune signatures and basal-like PAM50 signature (p<0.001, Spearman coefficient=0.372 for TILs, from 0.354 to 0.648 for immune signatures). Conclusions: PAM50 intrinsic subtyping and TILs/immune signatures capture only partially overlapping information on the biology of HR+/HER2- BCs. Pts with HR+/HER2- BCs simultaneously showing features of biological aggressiveness and enhanced immunogenicity may represent the ideal candidates for the combination of ICI and chemo. [Table: see text]