Gut microbiome is associated with recurrence-free survival in patients with resected high-risk melanoma receiving adjuvant immune checkpoint blockade

# Gut microbiome is associated with recurrence-free survival in patients with resected high-risk melanoma receiving adjuvant immune checkpoint blockade *Published: 2026 Apr 17* bioRxiv. 2024 Apr 20:2024.04.16.589761. doi: 10.1101/2024.04.16.589761. Patients with resected, high-risk melanoma receive adjuvant immune checkpoint blockade (ICB), yet clinical benefit remains unpredictable, with 25%-40% of patients experiencing recurrence. To evaluate whether pre-treatment gut microbiome (GMB) features predict recurrence, we analyzed stool samples from 674 patients enrolled in a phase 3 clinical trial, CheckMate 915, which investigated the combination of nivolumab plus ipilimumab versus nivolumab as a single agent across five geographic regions. Region-specific and cross-region meta-analyses identified pre-treatment taxa associated with recurrence, including Eubacterium, Ruminococcus, Firmicutes, and Clostridium. Recurrence prediction was strongest when the validation cohort exhibited GMB profiles similar to those in the discovery cohort. Among closely matched individuals (Jensen-Shannon divergence [JSD] ≤ 0.11), the area under the curve (AUC) for recurrence prediction ranged from 0.78 to 0.94 across regions. GMB composition remained largely stable following treatment. These findings suggest that gut bacterial markers can predict recurrence after adjuvant ICB treatment in melanoma, supporting their potential as clinically actionable biomarkers to guide personalized therapy. DOI: 10.1016/j.cell.2026.03.041