CNS Protection and Risk of Brain Metastases

Dr. Gumbleton addresses the central nervous system (CNS) implications of Mrs. Chen's disease. Although her baseline brain MRI is negative, her TP53 co-mutation is associated with a higher risk of CNS progression, and most patients with EGFR-driven NSCLC, approximately three-quarters, will develop brain metastases at some point in their disease course. Given this high lifetime risk and the fact that Mrs. Chen will not be undergoing serial brain MRIs more than approximately every 3 months, Dr. Gumbleton emphasizes choosing a regimen that protects the brain as much as possible.

From MARIPOSA, approximately twice as many patients remained free of CNS progression at 3 years with amivantamab plus lazertinib compared with osimertinib monotherapy—roughly one-third versus one-sixth at 3 years. The intracranial response rate with the combination was approximately 80%. Among patients with baseline brain metastases, progression-free survival (PFS) was significantly improved at about 18 months with the combination versus about 13 months with osimertinib alone.

FLAURA2 similarly showed better CNS protection with osimertinib plus chemotherapy compared with osimertinib alone, including improved 3-year overall survival (OS) and PFS in patients with baseline CNS disease. Dr. Gumbleton acknowledges cross-trial CNS comparison is limited because MARIPOSA required serial brain MRIs for all patients, whereas FLAURA2 required them only for those with known baseline CNS involvement. His overall conclusion: both combination regimens are clearly superior to osimertinib monotherapy for CNS protection.

In the next episode, “Safety Profiles and Proactive Adverse Event Management,” Dr. Gumbleton walks through the distinct adverse event profiles of the two combination regimens.