Comparative Analysis of Intracranial Response Assessment Criteria in Patients With Melanoma Brain Metastases Treated With Combination Nivolumab + Ipilimumab in CheckMate 204.

Purpose: In CheckMate 204, nivolumab + ipilimumab showed high intracranial (IC) objective response rates (icORRs) in patients with melanoma brain metastases (MBMs). Using icORR as a surrogate for overall survival (OS) has prompted use of alternate response criteria. To set the stage for harmonized MBM trials, the aim of this exploratory analysis was to determine icORR using several response criteria and examine correlations of response with survival.

Methods: Patients (N = 119) with ≥one unirradiated MBMs received nivolumab + ipilimumab every 3 weeks (four doses), followed by nivolumab every 2 weeks for ≤24 months. Blinded review icORR was assessed with modified RECIST (mRECIST), Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM; 5 mm and 10 mm cutoffs), and volumetric criteria (5 mm and 10 mm). Using a 6-week response landmark, IC progression-free survival (icPFS) and OS were compared for responders versus nonresponders.

Results: icORR was higher with mRECIST and volumetric criteria than with RANO-BM or RECIST. mRECIST and volumetric response also showed stronger correlations with icPFS and OS. mRECIST responders who were RANO-BM 5 mm nonresponders (n = 14) had similar OS to RANO-BM 5 mm responders (n = 41). Clinical deterioration affected RANO-BM icORR; however, when assessed only radiographically without deterioration, RANO-BM 5 mm performed similarly to mRECIST. Among 41 patients with target lesions all <10 mm, responder icPFS and OS were similar to those of responders in the total population, indicating that response could be accurately determined in these patients.

Conclusion: This analysis supports mRECIST or radiographic-only RANO-BM 5 mm as reliable assessment scales in MBM trials. Volumetric response correlated with survival, supporting its application in future trials. Response could be accurately determined in patients with MBMs all <10 mm, supporting the inclusion of patients with MBMs ≥5 mm in future trials.