Immunotherapy With Chemotherapy and Chemoradiation for Advanced Squamous Cancer of Nasal Cavity / Paranasal Sinuses (I-NAPA)

Inclusion Criteria: * Male/female participants who are at least 18 years of age on the day of signing informed consent with newly diagnosed, previously untreated, histologically and/or cytologically confirmed diagnosis of Stage II-IVb PNS SCC will be enrolled in this study. * Male participants: A male participant must agree to use a contraception as detailed in Appendix 3 of this protocol during the treatment period and for at least 150 days after the last dose of study treatment and refrain from donating sperm during this period. -Female participants: A female participant is eligible to participate if she is not pregnant (see Appendix 3), not breastfeeding, and at least one of the following conditions applies: 1. Not a woman of childbearing potential (WOCBP) as defined in Appendix 3 OR 2. A WOCBP who agrees to follow the contraceptive guidance in Appendix 3 during the treatment period and for at least 150 days after the last dose of study treatment. * The participant (or legally acceptable representative if applicable) provides written informed consent for the trial. * Have measurable disease based on RECIST 1.1. * Have provided archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated. Formalin-fixed, paraffin embedded (FFPE) tissue blocks are preferred to slides. Newly obtained biopsies are preferred to archived tissue. * Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1. Have adequate organ function as defined in the following table (Table 1). Blood must be collected within 14 days prior to the start of study treatment. Exclusion Criteria: * A WOCBP who has a positive urine pregnancy test within 72 hours prior to treatment (see Appendix 3). If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required. * Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti PD L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4, OX 40, CD137). * Patients must not have received prior systemic anti-cancer therapy including investigational agents or radiation therapy for PNS SCC but could have received treatment for prior cancers if greater than 2 years (refer to Item 8 for further details).