Medial retropharyngeal nodal region sparing radiotherapy versus standard radiotherapy in patients with nasopharyngeal carcinoma: open label, non-inferiority, multicentre, randomised, phase 3 trial

Objectives To address whether sparing the medial retropharyngeal lymph node (MRLN) region from elective irradiation volume provides non-inferior local relapse-free survival versus standard radiotherapy in patients with nasopharyngeal carcinoma. Design Open-label, non-inferiority, multicentre, randomised, phase 3 trial. Setting Three Chinese hospitals between 20 November 2017 and 3 December 2018. Participants Adults (18-65 years) with newly diagnosed, non-keratinising, non-distant metastatic nasopharyngeal carcinoma without MRLN involvement. Interventions Randomisation was done centrally by the Clinical Trials Centre at Sun Yat-sen University Cancer Center. Eligible patients were randomly assigned (1:1; block size of four) to receive MRLN sparing radiotherapy or standard radiotherapy (both medial and lateral retropharyngeal lymph node groups), and stratified by institution and treatment modality as follows: radiotherapy alone; concurrent chemoradiotherapy; induction chemotherapy plus radiotherapy or concurrent chemoradiotherapy. Main outcome measures Non-inferiority was met if the lower limit of the one sided 97.5% confidence interval of the absolute difference in three year local relapse-free survival (MRLN sparing radiotherapy minus standard radiotherapy) was greater than −8%. Results 568 patients were recruited: 285 in the MRLN sparing radiotherapy group; 283 in the standard radiotherapy group. Median follow-up was 42 months (interquartile range 39-45), intention-to-treat analysis showed that the three year local relapse-free survival of the MRLN sparing radiotherapy group was non-inferior to that of the standard radiotherapy group (95.3% v 95.5%, stratified hazard ratio 1.04 (95% confidence interval 0.51 to 2.12), P=0.95) with a difference of −0.2% ((one sided 97.5% confidence interval –3.6 to ∞), P non-inferiority v 35.1%, P=0.01) and late dysphagia (24.0% v 34.3%, P=0.008). Patient reported outcomes at three years after MRLN sparing radiotherapy were better in multiple domains after adjusting for the baseline values: global health status (mean difference −5.6 (95% confidence interval –9.1 to –2.0), P=0.002), role functioning (−5.5 (–7.4 to –3.6), P10 points difference). Conclusion Compared with standard radiotherapy, MRLN sparing radiotherapy showed non-inferiority in terms of risk of local relapse with fewer radiation related toxicity and improved patient reported outcomes in patients with non-metastatic nasopharyngeal carcinoma. Trial registration ClinicalTrials.gov NCT03346109