Modified Neck Dissection (Levels I-V)

Oral cavity squamous cell carcinoma (OCSCC) frequently metastasizes to cervical lymph nodes, and the extent of neck dissection remains an area of ongoing debate in patients with clinically node-positive (cN1) disease. While modified neck dissection (MND, levels I-V) is widely practiced, selective neck dissection (SND, levels I-IV) may provide equivalent oncologic outcomes with reduced surgical morbidity. However, high-quality randomized evidence comparing these approaches is lacking. The ExteNT N1 Trial is a prospective, randomized, open-label, parallel-group clinical trial designed to compare selective neck dissection (levels I-IV) with modified neck dissection (levels I-V, preserving the spinal accessory nerve, internal jugular vein, and sternocleidomastoid muscle) in patients with resectable cN1 oral cavity squamous cell carcinoma. Eligible participants will be randomized in a 1:1 ratio to either treatment arm. The primary endpoint is 3-year regional recurrence-free survival (RRFS), along with postoperative quality of life measured using the Neck Dissection Impairment Index (NDII). Secondary endpoints include overall survival, disease-free survival, level-wise nodal involvement, nodal yield, shoulder function (Constant-Murley Score, SPADI, and Arm Abduction Score), postoperative complications including chyle leak, and other surgical morbidities. This trial aims to generate level I evidence regarding the optimal extent of neck dissection for cN1 OCSCC, balancing oncologic safety with preservation of postoperative function and quality of life.