Response To Salvage Chemotherapy After Progression On Immune Checkpoint Inhibitors In Patients With Squamous Cell Carcinoma Of The Head And Neck.

6015 Background: Immune checkpoint inhibitors (ICI) have shown efficacy in patients with recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN) with an overall response rate (ORR) ranging from 13 to 17%. Recent data suggest that exposure to ICI potentially improves ORR to salvage chemotherapy (SCT) in advanced non-small cell lung carcinoma. We evaluated responses to chemotherapy in R/M SCCHN patients after progression on ICI. Methods: A retrospective study was conducted at 4 French referral centers. Eligibility criteria were patients treated with ICI for R/M SCCHN, who progressed after treatment with ICI (primary or secondary resistant to ICI) and received SCT between September 2014 and January 2018 and for whom efficacy data were available. Clinical and radiological data were collected from review of medical records. Results: Of 232 patients treated with ICI (anti-PD-1, anti-PD-L1, anti-CTLA-4 and anti-KIR), 82 met eligibility criteria: 84% were male, median age was 60 years old. ICI was given as monotherapy in 45% of patients or as combination in 55%. SCT included taxane-based regimen (56%), platinum-based regimen (37%), and methotrexate (7%). Cetuximab was administered in combination with taxanes or platinum in 50% of patients. The median number of treatment lines prior to SCT was 2 (range 1-6). The ORR to SCT was 30% (95% confidence interval: 21%-40%). Three patients (4%) presented complete response and 22 patients (27%) had partial response. The disease control rate was 57%. The age at initiation of SCT, initial tumor location, number of prior chemotherapy regimens, type of chemotherapy prior to ICI, best response to ICI, site of relapse and ECOG at SCT were not significantly associated with response to SCT on univariate analysis. Conclusions: In R/M SCCHN pretreated with ICI, the ORR to SCT was 30% higher than figures of historical cohorts in this setting. This suggests that exposure to ICI may increase tumor sensitivity to chemotherapy. Further investigations are warranted.