A phase III trial has found that brain MRI surveillance alone improved cognitive failure-free survival compared with MRI surveillance plus prophylactic cranial irradiation in patients with small-cell lung cancer, the International Association for the Study of Lung Cancer said. Results from the international SWOG S1827 MAVERICK trial were presented at the association's 2026 World Conference on Lung Cancer, and the researchers said they support MRI surveillance alone as the standard of care for patients with SCLC.

Prophylactic cranial irradiation has been used for decades after initial therapy for SCLC, the association said, because studies carried out before MRI was routine showed that it reduced brain metastases and improved overall survival. MAVERICK was designed to establish whether modern MRI surveillance could allow patients to avoid PCI and its potential cognitive and other toxicities without compromising survival, the association said.

The trial enrolled 304 patients with limited-stage or extensive-stage SCLC between January 2020 and December 2025. All had completed initial therapy and had no brain metastases on MRI before enrolment. Participants were assigned at random to MRI surveillance alone or to MRI surveillance plus PCI at 25 Gy in 10 fractions. Brain MRIs were performed every three months during the first year and every six months during the second year, with cognitive testing at the same intervals; the assessments included the Hopkins Verbal Learning Test-Revised, Controlled Oral Word Association and Trail Making Test.

At a median follow-up of 22 months among living patients, MRI surveillance alone improved cognitive failure-free survival, the trial's primary endpoint, reducing the risk of cognitive failure or death by 40% compared with MRI plus PCI (HR 0.60; 90% CI 0.46-0.78; p=0.001). The association said the benefit was similar among patients with limited-stage and extensive-stage disease and regardless of whether patients received immunotherapy. A preliminary overall survival analysis conducted after 128 deaths showed no apparent difference between the two strategies (HR 0.90; 90% CI 0.67-1.20), with a final analysis planned after 190 deaths, and brain metastasis-free survival was not significantly different between the groups (HR 1.25; 90% CI 0.95-1.66).

Serious treatment-related adverse events were less frequent with MRI surveillance alone. Grade 3-5 adverse events occurred in 0.8% of patients receiving MRI surveillance alone compared with 7.9% of those receiving MRI plus PCI (p=0.004). One grade 5 encephalopathy event occurred in the MRI plus PCI group. Chad Rusthoven of the University of Colorado School of Medicine, who presented the study, said the benefit of MRI surveillance alone appeared consistent across patients with both limited-stage and extensive-stage disease, and that the results supported MRI surveillance alone as the standard of care.