Plasma-based tumor mutational burden (bTMB) as predictor for survival in phase III EAGLE study: Durvalumab (D) ± tremelimumab (T) versus chemotherapy (CT) in recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) after platinum failure.
Weimin Li, Sophie Wildsmith, Jiabu Ye, Han Si, Nassim Morsli, Philip He, Jagdish Shetty, Alejandro Yovine, Nicholas Holoweckyj, Rajiv Raja, Katia Real, Paul Scorer, Todd Hembrough, Jill Walker, Qu Zhang, Ricard Mesı́a, Robert I. Haddad, Lisa Licitra, Robert L. Ferris
Abstract
6511 Background: In NSCLC, bTMB assessed from circulating tumor DNA shows promise as a predictive survival biomarker for immunotherapy, but its value in R/M HNSCC is uncertain. We evaluated bTMB as a predictor of survival in R/M HNSCC. Methods: EAGLE (NCT02369874) was a randomized, open-label, phase 3 trial evaluating D (anti-PD-L1), or D+T (anti-CTLA-4), vs CT in R/M HNSCC. Patients (pts) with disease progression after platinum-based CT were randomized (1:1:1) to D (10 mg/kg intravenous [IV] every 2 weeks [Q2W]), D (20 mg/kg IV Q4W) + T (1 mg/kg IV Q4W for up to 4 doses, followed by D at 10 mg/kg Q2W) or CT. bTMB was assessed in pretreatment plasma samples using the Guardant Health OMNI platform. Association of somatic loss of function mutations with OS was assessed. Results: 736 intent-to-treat pts were randomized; 247 were evaluable for bTMB (BEP). bTMB expression was not linked to HPV status, PD-L1 status, age, gender, tumor location, or ECOG PS. Smoking and progression within 6 months on multi-modality CT in localized disease trended with higher bTMB. OS and PFS HRs were significantly improved for D or D+T vs CT in pts with high bTMB (≥16 mut/Mb) vs low (<16 mut/Mb; Table). The benefit of D or D+T vs CT in pts with high bTMB generally improved with increasing cutoff. 74 pts (27 D, 20 D+T, 27 CT pts) were bTMB high. 18-month OS rates were higher for D+T (22%; 95% CI 7%–42%) and D (33%; 95% CI 17%–51%) vs CT (0%; 95% CI 0%–0%) in pts with high bTMB. Pts with mutations in KMT2D, a HNSCC tumor suppressor gene, showed improved OS for D+T vs CT (HR 0.39; 95% CI 0.18–0.85). A trend of improved OS for D+T vs CT (HR 0.19; 95% CI 0.03–1.03) was also seen in pts with ATM mutations. Conclusions: This is the first retrospective analysis of a phase 3 trial to show bTMB may be predictive of outcomes for checkpoint inhibitors in R/M HNSCC. In pts with high bTMB, D or D+T improved OS hazards by at least 60%, vs CT at cutoffs ≥16 mut/Mb. Validation of bTMB as a predictive biomarker is ongoing. Clinical trial information: NCT02369874 . [Table: see text]