What is the role of postoperative re-irradiation in recurrent and second primary squamous cell cancer of head and neck? A literature review according to PICO criteria

Head and neck squamous cell cancer; Radiotherapy; Re-irradiation; Recurrence; Retreatment; Squamous cell carcinoma; Carcinoma, Squamous Cell; Head and Neck Neoplasms; Humans; Neoplasm Recurrence, Local; Neoplasms, Second Primary; Randomized Controlled Trials as Topic; Re-Irradiation; Treatment Outcome; Hematology; Oncology; Geriatrics and Gerontology