Patients with locally advanced (stage III to stage IVB) poorly differentiated head and neck squamous cell carcinoma (excluding nasopharyngeal carcinoma) who meet the inclusion criteria will have their blood samples collected, tumor tissue samples or patient paraffin tissue, and slides for comprehensive genomic sequencing and analysis. The study is divided into two groups. Arm1 group: Patients with stage IVB (T4bNxM0) poorly differentiated head and neck squamous cell carcinoma (excluding nasopharyngeal carcinoma) will receive PD-1 combined with platinum-based chemotherapy and albumin-bound paclitaxel (dose according to the drug instructions) for 2 to 3 cycles (determined by the researcher based on tumor shrinkage). If the imaging achieves complete response (CR) or partial response (PR), suitable patients will undergo surgical treatment. Patients who are not suitable for surgery or have stable disease (SD)/progressive disease (PD) will receive concurrent chemoradiotherapy or concurrent chemoradiotherapy combined with PD-1 treatment (up to a total of 17 cycles). Arm2 group: Patients with stage III and IVA (T3NxM0, T4aNxM0) poorly differentiated head and neck squamous cell carcinoma (excluding nasopharyngeal carcinoma) will receive PD-1 combined with platinum-based chemotherapy and albumin-bound paclitaxel (dose according to the drug instructions) for 2 cycles. Patients who undergo surgery within 2 weeks will receive PD-1 monotherapy maintenance treatment or low-dose radiotherapy followed by PD-1 monotherapy maintenance treatment based on pathological results. Patients who do not achieve pathological complete response (pCR) and have positive surgical margins or extracapsular extension will receive concurrent chemoradiotherapy followed by PD-1 maintenance treatment (up to a total of 17 cycles). Patients without high-risk factors will receive PD-1 maintenance treatment after radiotherapy (up to a total of 17 cycles). After completion of treatment, all patients will be followed up every 3 months for 1 year. Subsequently, patients will be followed up every 6 months for 3 years. Thereafter, patients will be followed up annually. Patient recurrence and survival data will be recorded.