Toripalimab With Chemotherapy for Sinus Cancer

Inclusion Criteria: * Participants must have histologically or cytologically confirmed locoregionally advanced nasal cavity or paranasal sinus cancer including the following histologic subtypes: squamous cell carcinoma (SCC) of any morphologic variation: verrucous, papillary, basaloid, spindle cell, and adenosquamous; or sinonasal undifferentiated carcinoma (SNUC). * Participants with SCC should have resectable disease at baseline per the discretion of the treating surgical oncologist(s). \*Participants with SNUC can have operable or borderline resectable (definition: resection would been morbid requiring extensive surgery and would have chances of incomplete gross total resection) disease as judged by the treating surgical oncologist(s). * Participants must have clinical stage disease as defined below using the 8th (2017) edition of the tumor, node, metastasis (TNM) staging system by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC): * T2, N1-3 III * T3, any N III, IVA, IVB * T4, any N IVA, IVB * Participants must be willing to provide blood and tissue pre-treatment and at the time of surgery for pathologic and correlative analyses. * Age 18 years or older at the time of informed consent. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Participants must have adequate organ and marrow function as defined below: * Absolute neutrophil count ≥1000/mcL * Platelets ≥100 * Total bilirubin ≤…