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Updated Efficacy Of First Or Second-Line Pembrolizumab Plus In Metastatic Triple Negative Breast Cancer And Correlations With Baseline Lymphocyte And Naïve Cd4+ T-Cell Count, David Page, Joanna Pucilowska, Laura Bennetts, I Kim, Katherine Sanchez, Maritza Martel, Alison Conlin, Nikki Moxon, Staci Mellinger, Anupama Acheson, K Kemmer, Z Mitri, J Vuky, J Ahn, C Abaya, T Manigault, R Basho, Walter Urba, Hl Mcarthur

Books, Presentations, Posters, Etc.

Background: In mTNBC, anti-PD-1/L1 monotherapy is most effective when administered early in the course of disease, with recent trials demonstrating overall response rates (ORR) of 23-26% in the first-line setting and 5-6% in later lines. This may reflect iatrogenic lymphopenia from preceding cytotoxic chemotherapy. Furthermore, curative-intent chemotherapy is associated with prolonged suppression of naïve CD4+ cells, a T-cell subset that may play a critical role in the generation of de novo anti-tumor immune responses. We present the final clinical results of a pilot study evaluating the safety and efficacy of combining pembrolizumab plus standard-of-care capecitabine in the first/second-line mTNBC …