Overall Survival, Treatment Duration, and Rechallenge Outcomes With ICI Therapy for Recurrent or Metastatic HNSCC.

Importance: Immune checkpoint inhibition (ICI) is a frontline treatment for recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC), but questions remain surrounding optimal duration of therapy, benefits and risks of ICI rechallenge, and efficacy in first vs subsequent lines of therapy. Objectives: To estimate survival in US patients receiving ICI-based treatment for R/M HNSCC, compare outcomes associated with treatment discontinuation vs continuation at 1 or 2 years, and assess outcomes after immunotherapy rechallenge. Design, Setting, and Participants: This retrospective, population-based cohort study included adult patients in the Flatiron Health nationwide oncology database treated with immunotherapy for R/M HNSCC from 2015 to 2023. Data cutoff was August 31, 2023; data analysis was conducted from December 2023 to February 2024. Exposures: Treatment continuation vs discontinuation at 1 and 2 years; rechallenge with ICI after at least a 60-day period off ICI therapy without intervening systemic treatment (immediate rechallenge), or with intervening systemic treatment (delayed rechallenge). Main Outcomes and Measures: Overall survival (OS) from ICI initiation was analyzed using the Kaplan-Meier method. Cox multivariable regression was used to examine associations of key variables (line of therapy, human papillomavirus [HPV] status, Eastern Cooperative Oncology Group [ECOG] performance status) with survival. Results: The cohort included 4549 patients with R/M HNSCC who received ICI-containing therapy (median [IQR] age, 66 [59-72] years; 3551 [78.1%] male; 56 [1.2%] Asian, 260 [5.7%] Black or African American, 3020 [66.4%] White, 1213 [26.7%] other or unknown race; 3226 [70.9%] ECOG performance status 0 or 1). There were 3000 patients (65.9%) who received ICI in frontline and 1207 (26.5%) in second line; 3478 patients (76.5%) received ICI monotherapy. Median (IQR) OS was 10.9 (4.1-29.1) months and was longer in patients who received ICI in frontline therapy (12.2 [4.8-32.0] vs 8.7 [3.2-22.4] months), had HPV-positive cancer (16.6 [6.5-43.9] vs 8.8 [3.5-24.0] months), and had ECOG performance status 0 or 1 (13.5 [5.2-33.9] vs 5.5 [2.0-13.7] months). There were no survival differences on adjusted analysis between patients who stopped vs those who continued ICI at 1 or 2 years. Median (IQR) OS after ICI rechallenge was 15.7 (13.7-21.9) months in the immediate rechallenge group and 9.9 (3.7-18.1) months in the delayed rechallenge group. Conclusions and Relevance: In this large cohort study of patients with R/M HNSCC receiving ICI-based therapy, survival estimates closely mirrored clinical trial results, both in frontline and later-line settings. Discontinuation of ICI in long-term responders at 1 or 2 years may be a reasonable strategy that does not appear to compromise survival. ICI rechallenge was associated with clinical benefit in a subset of patients.