Impact of lymphopenia on efficacy of nivolumab in head and neck cancer patients

Introduction Lymphopenia has been correlated with poorer survival in patients with metastatic cancers treated with anti-PD-1 immunotherapy. Treatments such as chemotherapy, surgery or radiotherapy can induce lymphopenia. Radiation-induced lymphopenia is common and prolonged in head and neck cancer (HNSCC) patients. We evaluated the impact of lymphopenia, on efficacy of anti PD-1 nivolumab immunotherapy in HNSCC patients. Methods a multicenter retrospective study included consecutive patients treated with nivolumab for recurrent/metastatic (R/M) HNSCC between January 2017 and June 2019. Lymphopenia was defined as lymphocyte counts below 1000 cells/mm(3) upon initiation of nivolumab. Logistical regression was performed on factors associated with lymphopenia and ROC analyses assessed association between lymphopenia and survival. Results median age was 65. Of the 100 included patients, 60% had been treated by surgery, 67% had had first-line chemotherapy, and 89% loco-regional radiotherapy, 65% had concurrent chemotherapy with radiotherapy. Lymphopenia occurred in 56 (56%) patients upon initiation of nivolumab, with 29 (29%) patients having radiation-related lymphopenia. Prior locoregional radiotherapy was the only factor associated with lymphopenia upon initiation of nivolumab by logistical regression (OR 0.144 [0.029-0.706], p - 0.017). Lymphopenia upon initiation of nivolumab did not affect progression-free survival (PFS) (p - 0.815), overall survival (OS) (p - 0.783) or disease control rate (DCR) (p - 0.125). Locoregional symptomatology (HR - 2.37 [1.24-4.54], p - 0.009), metastatic symptomatology (HR - 4.74 [2.21-10.15], and persistent lymphopenia under nivolumab (HR 3.96 [1.19-13.17] p - 0.034) were associated with poorer OS in multivariate analysis. Conclusions Lymphopenia upon initiation of nivolumab was not associated with poorer survival in R/M HNSCC patients, but persistence of lymphopenia during immunotherapy might be a prognostic marker of patient survival.