Plasma Calcitonin Gene-Related Peptide (CGRP) Levels in Patients With Head and Neck Malignancies Undergoing Radiotherapy

Inclusion Criteria: * Age ≥ 18 years Histologically confirmed head and neck malignancy Planned to receive definitive or postoperative adjuvant radiotherapy Radiotherapy duration ≥ 4 weeks, with irradiation field involving the oral cavity, pharynx, or neck region Able and willing to provide written informed consent Able to complete pain assessments and blood sample collection Exclusion Criteria: * History of significant chronic pain prior to radiotherapy (e.g., postherpetic neuralgia, rheumatoid arthritis) Presence of uncontrolled hypertension, diabetes, or migraines Presence of other active malignancies or major systemic diseases (e.g., severe hepatic or renal dysfunction) Currently receiving or recently received treatments that may significantly affect pain perception (e.g., opioids, antidepressants) Pregnant or breastfeeding Inability to complete follow-up or poor treatment compliance