CNS Monitoring and When to Defer Local Therapy

Estelamari Rodriguez, MD, MPH, of Sylvester Comprehensive Cancer Center contrasts central nervous system (CNS) imaging in the phase 3 MARIPOSA and FLAURA2 studies of epidermal growth factor receptor (EGFR)-mutated advanced non–small cell lung cancer (NSCLC), noting that one scanned every patient on a set schedule while the other continued imaging mainly in patients with baseline brain metastases. Siddhartha Devarakonda, MD, of Providence Swedish Cancer Institute says the tighter schedule yields more precise estimates and gives him confidence the regimen is active in the CNS, though he is candid that the mechanism is unsettled. In practice he scans asymptomatic patients roughly every 3 to 6 months and patients with baseline brain metastases every 3 to 4 months, citing how burdensome frequent magnetic resonance imaging is. With regimens this active, he is comfortable deferring local therapy in asymptomatic patients given the cumulative risk of radiation necrosis.