CLEAR (Cervical Lymphatic Exclusion in Adjuvant Radiation)

Inclusion Criteria: * Patients ≥ 18 years of age * ECOG Performance Status (PS) ≤ 2 * Histologically confirmed diagnosis of locally advanced squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx * Resection of the primary tumor and unilateral and/or bilateral neck dissection performed according to standard guidelines, with detailed histological reporting by nodal level * Number of lymph nodes per dissected neck ≥ 18 * No pathological lymph nodes following neck dissection (pN0) * Presence of a single pathological cervical lymph node following neck dissection (pN1), provided that: * No extracapsular extension * Diameter \< 1 cm * No skip metastasis * Presence of risk factors indicating postoperative radiotherapy. Stages pT1-pT2N1 and pT3-pT4N0/N1. If N1, all of the following criteria must be met: presence of a single cervical lymph node without extracapsular extension, diameter \< 1 cm, and no skip metastasis * Patients may receive adjuvant systemic treatment if surgical margins are positive or close (\< 5 mm) Exclusion Criteria: * Absence of informed consent * Prior irradiation to the head and neck region * Prior surgery in the head and neck region * Contralateral neck dissection not performed when clinically indicated * History of malignancy within the previous 5 years, with the exception of non-melanoma skin cancer * Interval between surgery and radiotherapy \> 8 weeks