Medial retropharyngeal nodal region sparing radiotherapy for nasopharyngeal carcinoma

1. In this noninferiority trial, medial retropharyngeal lymph node (MRLN)-sparing radiotherapy was found to be noninferior with respect to local relapse-free survival when compared to standard radiotherapy encompassing all retropharyngeal lymph nodes in patients with non-metastatic nasopharyngeal carcinoma.

Retropharyngeal lymph nodes (RLN) are paired groups of lymph nodes in the suprahyoid portion of the retropharyngeal space and comprise medial (MRLN) and lateral (LRLN) groups. Due to their involvement as first echelon raining nodes for nasopharyngeal carcinoma and high proportion of involvement at initial diagnosis, complete coverage of MRLN and LRLN during radiotherapy has been the standard of care. However, radiation of the MRLN also exposes pharyngeal constrictors to a relatively high dose of radiation, and reports suggest high proportions of late dysphagia and silent aspiration, resulting in poor quality of life. Previous investigations have found that retropharyngeal lymph node involvement mainly occurs in the lateral group, and a retrospective study recently showed that exclusion of the MRLN region from elective radiotherapy still resulted in no recurrence. This noninferiority trial aimed to compare outcomes of MRLN-sparing radiotherapy versus standard radiotherapy (encompassing both MRLN and LRLN regions). Patients were randomly assigned in a 1:1 ratio to receive either MRLN-sparing radiotherapy or standard radiotherapy. The primary outcome investigated was local relapse-free survival. Between November 2017 and December 2018, 568 patients were recruited at three major hospitals in China, with 285 patients randomly assigned to the MRLN-sparing radiotherapy group and 283 patients assigned to the standard radiotherapy group. At the time of analysis, three-year visit forms were available for 540 (95.1%) of the 568 patients. With respect to the primary outcome, local recurrence was recorded for 14 (4.9%) of patients in the MRLN-sparing radiotherapy group versus 12 (4.2%) in the standard radiotherapy group, with a majority o patients developing in-field recurrences. The three-year local relapse-free survival was 95.3% (95% confidence interval, 92.8% to 97.8%) in the MRLN-sparing radiotherapy group and 95.5% (95% CI, 93.0% to 98.0%) for the standard radiotherapy group (estimated absolute difference of -.02%; P<.001). Overall, the findings from this study suggest the non-inferiority of MRLN-sparing radiotherapy in comparison to standard radiotherapy in patients with non-metastatic nasopharyngeal carcinoma with respect to local relapse-free survival. The main limitation of this study was that the nasopharyngeal carcinomas in this population were almost all caused by the Epstein-Barr virus, which may not be generalizable to different patient populations. This study is the first to study the noninferiority of MRLN-sparing radiotherapy compared to standard radiotherapy for nasopharyngeal carcinoma and will serve as a guide for the design of future randomized controlled trials.

Click to read the study in BMJ

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