Abstract PS13-10: Impact of BRCA mutation status on immune infiltration, chemosensitivity, and prognosis of breast cancer patients treated with neoadjuvant chemotherapy

Context: The majority of BRCA mutation carriers diagnosed with breast cancer (BC) are treated with chemotherapy. The effectiveness of standard neoadjuvant chemotherapy (NAC) in BRCA associated BC compared to noncarriers has been poorly explored. Objectives: To assess whether the BRCA mutation status modifies the immune infiltration, chemosensitivity, and prognosis of breast cancer. Methods: We retrospectively identified in our institutional database all consecutive patients with BRCA germline mutation status available treated with NAC between 2002 and 2012. Microbiopsy specimens and paired surgical samples were evaluated for pre-NAC and post-NAC immune infiltration (stromal TILs, str TILs; intratumoral TILs, IT TILs). Response to chemotherapy was assessed by pathological complete response (pCR) rates. Association of clinical and pathological factors with pCR, overall survival (OS), and relapse free survival (RFS) was assessed by univariate and multivariate analyses. Results: Overall, 267 patients were included in this study (46 BRCA carriers and 221 BRCA noncarriers). The median age at BC diagnosis was 40 years old, and most of the patients (n=227, 85%) were premenopausal. Patients repartition by subtype was as follows: luminal (n=90, 33.7%), TNBC (n=110, 41.2%), HER2-positive (n=67, 25.1%). BRCA mutation carriers were likely to have familial history of BC (73.9% vs. 52.3%, p = 0.012), and be diagnosed with TNBC (58.7% vs 37.6%; p = 0.006), than noncarriers. No pattern was significantly different between BRCA mutation subgroups regarding age, body mass index, histology, tumor size, grade or Ki67. TIL levels were available in 192 patients. Neither pre-NAC stromal TIL levels nor IT TILs were significantly different by BRCA status in the whole population, nor in each BC subtype. PCR rates were significantly higher in BRCA mutation carriers (p= 0.035), and this association remained statistically significant only in the luminal BC subtype (p=0.006) after stratification by BC subtype (Pinteraction= 0.056). After multivariate analysis, only BC subtype and pre-NAC str TILs were independent predictors of pCR. Post-NAC stromal and intra-tumoral TIL levels were significantly higher luminal subtype (p=0.009 and p=0.019, respectively). After a median follow-up of 90 months, RFS and OS were not different between BRCA carriers and noncarriers, neither in the whole population nor after stratification by BC subtype. Discussion: In our study, BRCA status was associated with an enhanced response to standard NAC, particularly in luminal BC patients, in addition to higher post-NAC TIL levels. Whether patients with luminal BC and BRCA mutation derive benefit from second line immunotherapy after NAC completion remains to determine. Citation Format: Beatriz Grandal, Clemence Evrevin, Eric Daoud, Elise Dumas, Nadir Sella, Clara Sebbag, Sonia Rozette, Isabelle Jardin, Lucie Laot, Florence Coussy, Claire Saule, Dominique Stoppa-Lyonnet, Sophie Franck, Claire Senechal, Enora Laas, Marick Lae, Diane De Croze, Fabien Reyal, Anne-Sophie Hamy. Impact of BRCA mutation status on immune infiltration, chemosensitivity, and prognosis of breast cancer patients treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-10.