CD274 and head and neck squamous cell carcinoma: An ongoing study will evaluate the efficacy of PARP/PD-L1 blockade (NCT04169841) and explore whether immunotherapy increases the duration of response to PARP inhibition in HNSCC or whether a third blocking agent such as a CSF1R inhibitor might be necessary to enhance innate and adaptive antitumor immunity and survival in patients with HNSCC.