We have made tremendous progress in cancer care via the use of immunotherapy; however, not all patients respond and toxicity to therapy may be limiting. It is becoming increasingly clear that responses to therapy are dependent on a number of factors that influence tumor growth and immunity—and that these all are inter-related. There is a growing appreciation of the role of environmental factors, such as the microbiome, on responses to therapy. The microbiome refers to microbes and their genomes within a given host, and there is a significant contribution of microbes to our overall cellular content and to our genomic content. There is now evidence that the gut microbiome may shape immunity and responses to immunotherapy, and efforts are ongoing to modulate the microbiome to enhance therapeutic responses. Additionally, there is evidence that microbes within tumors of patients with cancer may shape responses to therapy. Furthermore, microbes may also influence toxicity to cancer therapy. The use of the microbiome as a biomarker and a therapeutic target will be discussed, as will complexities and recommendations for a path forward to implement microbiome analyses and targeting in precision cancer care and overall precision health.

Citation Format: Jennifer A. Wargo. The role of the microbiome in response and toxicity to cancer therapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr IA23.