Immune Response Evaluation and Treatment with Immune Checkpoint Inhibitors Beyond Clinical Progression: Response Assessments for Cancer Immunotherapy

Purpose of Review This review provides a comprehensive assessment of recent literature reports describing atypical response patterns observed with immune checkpoint inhibitors (ICIs), modifications to response evaluation criteria for ICIs, and treatment beyond progression in clinical trials. Recent Findings Certain response patterns such as durable response, pseudoprogression, hyperprogression, and dissociated responses can be seen with ICI treatment. These patterns carry differing prognoses and are associated with varied factors. There are multiple modifications of standard Response Evaluation Criteria in Solid Tumors (RECIST) that have been proposed to better characterize immunotherapy response; however, standard RECIST1.1 remains most commonly used in clinical trials. Treatment beyond progression varies in frequency and benefit depending on assessment criteria and cancer type. Summary Future research incorporating modified imaging criteria and biomarker assessments may serve to clarify who will benefit most from treatment beyond progression.