Abstract PD9-04: Immunological and clinical consequences of durvalumab treatment in combination to neoadjuvant chemotherapy in triple-negative breast cancer patients

Abstract Background: The implementation of immune checkpoint inhibitors in the therapy of different cancer types has provided promising results, but only a limited number of patients respond. Therefore, biomarkers to identify these responding patients are urgently needed. Methods: The GeparNuevo was a randomized, double-blind phase II trial in which triple-negative breast cancer (TNBC) patients were treated with neoadjuvant chemotherapy (NACT) consisting of nanoparticle albumin-bound paclitaxel in an initial phase followed by treatment with epirubicin and cyclophosphamide. Placebo or durvalumab were given throughout the neo-adjuvant treatment and in the “window” sub-cohort also prior to chemotherapy. Primary objective of this report was to evaluate changes in the blood immune cell repertoires of TNBC patients receiving durvalumab (anti-PD-L1) versus placebo in combination with NACT. At up to 4 different time points during therapy, blood samples were taken and underwent immunomonitoring using multicolor flow cytometry. The absolute counts of the major immune cell subtypes in the blood as well as the frequencies of different immune cell subpopulations and their functional phenotypes along treatment were determined and correlated to clinico-pathologic characteristics of the patients and to treatment response. Results: 120 out of 174 patients included in the GeparNuevo trial underwent blood immunomonitoring; 63 patients belonged to the “window” sub-cohort. Durvalumab administration almost completely blocked the detection of the inhibitory ligand PD-L1 and induced changes in the composition of the immune cell subpopulations. Evaluation of the “window” sub-cohort, in which an enhanced, but not significant pathological clinical response was observed within the immunomonitored patients, identified different markers correlating with clinical response to durvalumab. Higher frequencies of CD4+ T cells at recruitment as well as increased frequencies of T cells bearing the gamma delta TCR along treatment were some of the characteristics of patients responding to durvalumab treatment. Conclusions: The flow cytometry-based immunomonitoring of the clinical trial identified different immune-relevant biomarkers at recruitment as well as during treatment that predict clinical response to durvalumab. After validation of this data in an independent patient cohort, these markers could be implemented for an improved patient stratification to immunotherapy. Citation Format: Chiara Massa, Thomas Karn, Karsten Weber, Andreas Schneeweiss, Claus Hanusch, Jens-Uwe Blohmer, Dirk-Michael Zahm, Christian Jackisch, Marion van Mackelenbergh, Jörg Thomalla, Frederik Marmé, Jens Huober, Volkmar Müller, Christian Schem, Anja Müller, Elmar Stickeler, Katharina Biehl, Peter A. Fasching, Michael Untch, Sibylle Loibl, Carsten Denkert, Barbara Seliger. Immunological and clinical consequences of durvalumab treatment in combination to neoadjuvant chemotherapy in triple-negative breast cancer patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD9-04.