This thesis examines the role of systemic therapies in head and neck tumors, focusing on cytotoxic chemotherapy, targeted therapies, and immunotherapy. The mechanisms, efficacy, and toxicity of chemotherapeutic agents such as alkylating agents, antimetabolites, and microtubule inhibitors are analyzed. Additionally, targeted therapies, including EGFR and VEGF inhibitors, as well as molecularly targeted agents affecting MET, mTOR, and EGFR pathways, are explored. The study also highlights immunotherapeutic approaches, particularly PD-1, PD-L1, and CTLA-4 inhibitors, as well as novel treatments such as cancer vaccines and adoptive cell transfer.