Association of Tumor Infiltrating Lymphocytes with Homologous Recombination Deficiency and BRCA1/2 Status in Patients with Early Triple-Negative Breast Cancer: A Pooled Analysis

Abstract

Background: Patients with triple-negative breast cancer (TNBC) with homologous recombination deficient tumors achieve significantly higher pathologic complete response (pCR) rates when treated with neoadjuvant platinum-based therapy. Tumor infiltrating lymphocytes (TILs) are prognostic and predictive of chemotherapy benefit in early stage TNBC. The relationship between TILs, BRCA1/2 mutation status and Homologous Recombination Deficiency (HRD) status in TNBC remains unclear. Experimental Design: We performed a pooled analysis of 5 phase II studies that included patients with TNBC treated with neoadjuvant platinum-based chemotherapy to evaluate the association of TILs with HRD status (Myriad Genetics) and tumor BRCA1/2 mutation status. Further, the relationship between pathologic response assessed using the residual cancer burden (RCB) index and HRD status with adjustment for TILs was evaluated. Results: Among 161 patients, stromal TIL (sTIL) density was not significantly associated with HRD status (p=0.107) or tumor BRCA1/2 mutation status (p=0.391). In multivariate analyses, sTIL density (OR 1.23, 95% CI 0.94-1.61, p=0.139) was not associated with pCR, but was associated with RCB 0/I status (OR 1.62, 95% CI 1.20-2.28, p=0.001). HRD was significantly associated with both pCR (OR 12.09, 95% CI 4.11-44.29, p= 7.82 x10^-7) and RCB 0/I (OR 10.22, 95% CI 4.11-28.75, p= 1.09 x10^-7) in these models. Conclusions: In patients with TNBC treated with neoadjuvant platinum-based therapy, TIL density was not significantly associated with either tumor BRCA1/2 mutation status or HRD status. In this pooled analysis, HRD and sTIL density were independently associated with treatment response, with HRD status being the strongest predictor.