Abstract 1618: Immune-modulating effect of bevacizumab in EGFR mutated lung adenocarcinoma

Abstract Background: Host immunity affect treatment effect of lung cancer. Peripheral blood S100A9+ monocytic myeloid derived suppressor cells (MDSCs) is a predictive factor for treatment response of chemotherapy and epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) of lung adenocarcinoma patients. Bevacizumab have immune-modulating effect, including decreasing MDSCs, and improve treatment effect in combination with immunotherapy. However, the effect of immune modulation in combination of bevacizumab and EGFR-TKI in EGFR mutated lung adenocarcinoma patients is not clear. Methods: Stage IV lung adenocarcinoma harboring sensitive EGFR mutation patients receiving first line EGFR-TKI or combination EGFR-TKI and bevacizumab were enrolled. The peripheral blood mononuclear cell (PBMCs) were collected, and S100A9+ MDSCs percentage was calculated by flow cytometry from CD14+S100A9+ in PBMC. Clinical data was collected. Results: Eight patients receiving EGFR-TKI and bevacizumab, as combination group, and twenty patients received EGFR-TKI alone, as control group, were enrolled. PBMC S100A9+ MDSC decreased in combination group (decrease 39±18% from baseline), but not in control group. Combination group had longer progress free survival (PFS) comparing with control group. (Median PFS combination vs control group: 15.2 vs 9.9 months, Log Rank test, p=0.05) Increased of peripheral blood cytotoxic T cells also had trend in combination group but not in control group. Conclusion: Besides the anti-angiogenesis effect, bevacizumab had immune modulated effect, especially in decreasing circulating S100A9+ MDSC in EGFR mutated lung adenocarcinoma patients. This might partially explain the longer PFS in combination of EGFR-TKI of anti-angiogenesis agent treatment. Citation Format: Po-Hao Feng, Kang-Yun Lee. Immune-modulating effect of bevacizumab in EGFR mutated lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1618. doi:10.1158/1538-7445.AM2017-1618