ABSTRACT Support is requested for a Keystone Symposia conference entitled Advances in Cancer Immunotherapy, organized by Drs. Antoni Ribas, W. Nicholas Haining and Priti Hegde. The conference will be held in Whistler, British Columbia Canada from March 22-26, 2020. Cancer immunotherapy by blocking immune inhibitory checkpoints or engineering T cells for adoptive cell transfer is providing an unprecedented level of long-term antitumor activity in patients with several metastatic cancers. However, the majority of patients with advanced cancers still do not experience sustained clinical benefit from immunotherapy. Understanding the mechanistic basis of response and resistance to these therapies and how therapeutic approaches could best be combined will be essential to continue progress. The largest human experiment is currently being conducted with over 1,000 agents and combinations. Understanding the results to date and determining what is working and what combinations are not working will be important to refine our understanding of immunity in patients with cancer. Questions that remain unanswered include: What is the rationale for the multiple immuno-oncology (IO) combinations being tested in the clinic, how do cancers adapt and resist T cell attack, and can we better understand the tumor microenvironment, thus paving the way for new approaches to cancer therapy. New analyses of patient- derived samples provide information on adaptive and genetic resistance mechanisms to immunotherapy. The conference program will include sessions which cover topics such as new analysis techniques, methodologies, and how to integrate high throughput data to provide a more comprehensive understanding of cancer and the immune system. Participants will leave the conference with an understanding of how the advancement of cancer biology will be influenced by a better comprehension of tumor immunology.