Results from the SWOG S1827 MAVERICK phase III trial, presented at the IASLC World Conference on Lung Cancer 2026 in Seoul, South Korea, indicate that brain MRI surveillance alone is superior to MRI surveillance combined with prophylactic cranial irradiation (PCI) for patients with small-cell lung cancer (SCLC) who have completed initial therapy and have no evidence of brain metastases.
MRI surveillance without PCI significantly improved cognitive failure-free survival (CFFS) compared with MRI plus PCI (HR 0.60, 90% CI 0.46–0.78, p=0.001), with a preliminary overall survival (OS) analysis showing no significant difference between arms. The OS non-inferiority analysis remains preliminary, as the final analysis is prespecified to occur after 190 deaths; only 128 deaths had been observed at the time of this report.
Key finding
In the MAVERICK trial, MRI surveillance alone significantly improved cognitive failure-free survival over MRI plus PCI in SCLC patients, with a consistent benefit across disease stages and immunotherapy use, though the OS non-inferiority analysis has not yet reached its prespecified event threshold.
Study Design
| Trial | SWOG S1827 MAVERICK — international, randomized phase III trial |
|---|---|
| Population | Patients with limited-stage (LS) or extensive-stage (ES) SCLC who had completed initial therapy with no brain metastases on MRI at enrollment; 304 patients randomized (68% LS-SCLC); enrollment January 2020 – December 2025 |
| Treatment | MRI surveillance alone vs. MRI surveillance plus PCI (25 Gy in 10 fractions); MRI performed every 3 months in year 1 and every 6 months in year 2 in both arms |
| Primary endpoint | Cognitive failure-free survival (CFFS): time to first cognitive failure on any test (Hopkins Verbal Learning Test-Revised, Controlled Oral Word Association, or Trail Making Test) or death |
| Key secondary endpoints | Overall survival (non-inferiority margin: upper bound of 90% CI ≤1.25; final analysis prespecified at 190 deaths); brain metastasis-free survival; treatment-related toxicities |
The trial was stratified by disease stage (LS vs. ES), receipt of immunotherapy, and performance status (ECOG 0–1 vs. 2). Cognitive testing was conducted at the same time points as MRI surveillance, providing a structured, longitudinal assessment of neurological function across both arms.
Results and Safety
The primary endpoint was met: MRI surveillance alone was associated with significantly improved CFFS compared with MRI plus PCI (HR 0.60, 90% CI 0.46–0.78, p=0.001). Subgroup analyses showed no meaningful variation in the CFFS benefit by disease stage (LS vs. ES; interaction p=0.92) or receipt of immunotherapy (interaction p=0.25), suggesting a consistent treatment effect across these prespecified subgroups.
A preliminary OS analysis at 128 deaths showed no significant difference between arms (HR for MRI alone vs. MRI plus PCI: 0.90, 90% CI 0.67–1.20). However, this analysis is interim; the trial’s prespecified non-inferiority assessment of OS requires 190 deaths, and the final OS results were not available at the time of presentation. Brain metastasis-free survival did not differ significantly between arms (HR 1.25, 90% CI 0.95–1.66).
The safety profile favored MRI surveillance alone. Treatment-related grade 3–5 adverse events occurred in 0.8% of patients in the MRI-alone arm versus 7.9% in the MRI plus PCI arm (p=0.004). One grade 5 encephalopathy was reported in the MRI plus PCI arm. No grade 5 events were reported in the MRI-alone arm.
Clinical Context
PCI has historically been a standard component of SCLC management, supported by pre-MRI era data demonstrating reductions in brain metastases and improvements in OS. However, its neurocognitive toxicity has long been a clinical concern, and the widespread adoption of routine brain MRI has altered the landscape by enabling early detection of brain metastases without irradiating patients prophylactically. MAVERICK is the largest randomized trial to formally test MRI surveillance as a standalone strategy in an era of modern imaging, and its investigators conclude that MRI alone should now be considered the standard of care for patients with SCLC after completion of initial therapy.
Key questions remain, however. The final OS non-inferiority analysis has not yet been reported, and longer follow-up will be needed to fully characterize survival outcomes, particularly in the context of evolving systemic therapies including immunotherapy. Additionally, whether specific subgroups, such as patients with LS-SCLC who achieve deep systemic responses, might derive differential benefit or harm from PCI omission warrants continued observation.
Sources
- IASLC World Conference on Lung Cancer 2026. Rusthoven CG et al. “SWOG S1827 MAVERICK: Phase III Trial of Brain MRI Surveillance +/- Prophylactic Cranial Irradiation for Small-Cell Lung Cancer.” Conference abstract presentation (Abstract PL02.01). Presented 2026, Seoul, South Korea. View source.
AI disclosure: This article was prepared with assistance from generative AI using the source material cited above. It was reviewed and edited by Brandon Twyford before publication.