Abstract Aim: Nivo is the only immunotherapy to significantly improve overall survival (OS) in patients (pts) with R/M SCCHN who have progressed on or after platinum-based therapy. Here we report long-term data from the randomized, open-label, phase 3 CheckMate 141 study (NCT02105636). Patients: Pts with R/M SCCHN who progressed on or after platinum-based therapy were randomized 2:1 to nivo 3 mg/kg q2wk (n = 240) or IC (methotrexate, docetaxel, or cetuximab; n = 121). Endpoints: OS (primary), progression-free survival (PFS), safety. Minimum follow-up: 24.2 mo (data cut: Sep 2017). Results: Nivo improved OS significantly vs IC in the overall population (median [95% CI]: 7.7 [5.7, 8.8] mo vs 5.1 [4.0, 6.2] mo; HR [95% CI]: 0.68 [0.54, 0.86]). 2-yr OS rate (95% CI) was 16.9% (12.4, 22.0) with nivo vs 6.0% (2.7, 11.3) with IC. 8.3% of pts in the IC arm received subsequent immunotherapy. Outcomes by PD-L1 and HPV subgroups are shown in the Table. In pts with tumor PD-L1 <1%, risk of death at 2 yrs was reduced by 27% with nivo vs IC with the HR trending lower with longer follow-up; HR (95% CI) = 0.89 (0.54, 1.45), 0.83 (0.54, 1.29), and 0.73 (0.49, 1.09) at 6 mo (Dec 2015 data cut), 1 yr (Sep 2016 data cut), and 2 yrs of follow-up, respectively. Nivo also continued to improve OS vs IC in pts with tumor PD-L1 ≥ 1%. Complete responses were noted in both PD-L1 ≥ 1% and <1% groups. Key baseline characteristics, including PD-L1 expression and HPV status, were similar among patients who survived 2 yrs compared with all patients in the nivo arm. Grade 3-4 treatment-related adverse events occurred in 15.3% (nivo) vs 36.9% (IC) of pts; toxicity-related deaths in 2 pts (0.8%) and 1 pt (0.9%), respectively. Conclusion: With 2-yr follow-up, nivo continued to significantly improve OS and maintain a favorable safety profile vs IC. Nivo is the only immunotherapy to demonstrate OS benefit irrespective of PD-L1 expression in pts with SCCHN. Table: Outcomes by PD-L1 expression and HPV statusMedian OS (95% CI), monthsMedian PFS (95% CI), monthsNivoICHR (95% CI)NivoICHR (95% CI)PD-L1 < 1%6.5 (4.4, 11.7)5.5 (3.7, 8.5)0.73 (0.49, 1.09)2.0 (1.9, 2.1)2.7 (2.0, 4.6)1.13 (0.75, 1.71)PD-L1 ≥ 1%8.2 (6.7, 9.5)4.7 (3.8, 6.2)0.55 (0.39, 0.78)2.1 (2.0, 3.5)2.0 (1.9, 3.1)0.59 (0.41, 0.84)HPV+9.1 (6.5, 11.8)4.4 (3.0, 9.8)0.60 (0.37, 0.97)2.0 (1.9, 3.3)2.0 (1.6, 2.8)0.75 (0.46, 1.23)HPV−7.7 (4.8, 13.0)6.5 (3.9, 8.7)0.59 (0.38, 0.92)2.1 (1.9, 3.1)3.3 (1.9, 4.0)1.01 (0.65, 1.56) Citation Format: Robert L. Ferris, George R. Blumenschein, Jerome Fayette, Joel Guigay, A Dimitrios Colevas, Lisa Licitra, Kevin J. Harrington, Stefan Kasper, Everett E. Vokes, Caroline Even, Francis Worden, Nabil F. Saba, Lara Carmen Iglesias Docampo, Robert Haddad, Tamara Rordorf, Naomi Kiyota, Makoto Tahara, Mark Lynch, Vijayvel Jayaprakash, Li Li, Maura L. Gillison. Nivolumab (Nivo) vs investigator's choice (IC) in recurrent or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN): 2-yr outcomes in the overall population and PD-L1 subgroups of CheckMate 141 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT116.