Medial retropharyngeal nodal region sparing radiotherapy in nasopharyngeal carcinoma: five year analysis of open label, non-inferiority, multicentre, randomised phase 3 trial

OBJECTIVE: To determine the pre-specified long term efficacy (survival and swallowing function) and safety of medial retropharyngeal lymph node (MRLN) region sparing radiotherapy for non-metastatic nasopharyngeal carcinoma. DESIGN: Pre-specified five year analysis of an open label, non-inferiority, multicentre, randomised phase 3 trial. SETTING: Three Chinese medical centres between 20 November 2017 and 3 December 2018. PARTICIPANTS: Adults (18-65 years) with untreated, non-keratinising, non-metastatic nasopharyngeal carcinoma without MRLN involvement. INTERVENTIONS: Eligible patients were randomised (1:1; block size of four) to MRLN sparing radiotherapy or standard radiotherapy. Randomisation was stratified by institution and treatment modality (radiotherapy alone, concurrent chemoradiotherapy, or induction chemotherapy plus radiotherapy or concurrent chemoradiotherapy). MAIN OUTCOME MEASURES: 2.15 mm; P=0.01) was less severe after MRLN sparing radiotherapy. CONCLUSIONS: MRLN sparing radiotherapy maintained uncompromised efficacy and better long term swallowing function by reducing radiation damage to pharyngeal contractors, supporting its use as a standard of care for non-metastatic nasopharyngeal carcinoma. TRIAL REGISTRATION: ClinicalTrials.gov NCT03346109.