Correlation between tumor size change and outcome in a rare cancer immunotherapy basket trial.

Percent change in tumor measurement per RECISTv1.1 (the sum of longest dimensions of target lesions) has a linear association with PFS and OS up to a 40% to 50% increase in tumor measurement in this cohort of patients with rare cancers who received combination immune checkpoint blockade. Quantitative first scan tumor measurement changes include important information to evaluate the potential efficacy of a therapy beyond the proportion of patients who achieve an objective response.