Go online to PeerView.com/GNU860 to view the activity, download slides and practice aids, and complete the post-test to earn credit. With the continued expansion of the cancer immunotherapy arsenal, reliable biomarkers to identify patients most likely to benefit from specific agents or combinations have become crucial. Predictive biomarkers such as measurement of PD-L1 expression and assessment of MSI/MMR or TMB status have an established role in some tumor types and settings, but a number of challenges related to testing and interpretation of results persist, and significant improvements are needed. There is also a need for ways to assess response to immunotherapies as they transition to early-stage, curative-intent settings as part of perioperative multimodal management of solid malignancies. Recently, pathologic response assessment has emerged as a potential new gold standard for measurement of impact of neoadjuvant immunotherapy. However, there has been limited guidance on how to define pathologic response, process and evaluate resected specimens, and report and apply assessment results in the settings of clinical trials and practice. This PeerView educational activity, based on a recent live symposium, focuses on current and emerging immunotherapy biomarkers, the rationale for and practicalities of biomarker testing as a guide for immunotherapy selection for different solid tumors, and the nuances of pathologic response assessment after neoadjuvant immunotherapy. Additionally, practical guidance is provided to help multidisciplinary coordination of care based on biomarker testing and pathologic response assessment so that more patients receive personalized immunotherapy and experience improved outcomes. Upon completion of this activity, participants should be better able to: Explain the evidence and rationale for the role of biomarkers to predict and assess response to cancer immunotherapy in metastatic and resectable solid malignancies; Conduct cancer immunotherapy biomarker testing and pathologic response assessment congruent with the latest evidence, requirements, and recommendations; and Personalize cancer immunotherapy treatment and response assessment by collaborating with multidisciplinary care team members to optimally select and interpret biomarkers.