Contralateral Neck Recurrence Rates After Ipsilateral Neck Adjuvant Radiation in Head and Neck Carcinomas with a Pathologically Negative Contralateral Neck

Introduction In 2019 we published a phase II trial of ipsilateral neck adjuvant radiation therapy in head and neck (HN) carcinoma patients with a pathologically negative (pN0) contralateral neck after bilateral neck dissection. The five-year contralateral neck recurrence rate was 3%. Here we present the recurrence rate in patients subsequently treated by this trial’s paradigm. Methods Patients were selected who would have been eligible for our phase II trial: all had oropharynx, hypopharynx, oral cavity, or unknown primary carcinomas without prior HN cancer or major HN surgeries, underwent primary resection including bilateral neck dissection with a pN0 contralateral neck, and underwent adjuvant intensity modulated radiation therapy (IMRT) that spared the contralateral neck. Results Fifty-five patients met cohort inclusion criteria. Thirty-nine cancers arose from the oropharynx, 11 from the oral cavity, three from the hypopharynx, and two from an unknown primary. With a median follow-up of 15 months there were nine recurrences (16%), four contralateral neck recurrences (7%), and one isolated contralateral neck recurrence (2%). No contralateral neck recurrences occurred in patients with p16+ oropharyngeal primaries despite that most (73%) arose from the base of the tongue. In contrast, three contralateral neck recurrences occurred in patients with advanced stage oral cavity primaries. Conclusion The contralateral neck recurrence rate in HN carcinoma patients with a pN0 contralateral neck treated by adjuvant ipsilateral neck IMRT was similar to the 3% rate observed in our phase II trial. However, this paradigm may be inadequate for patients with locally advanced oral cavity primaries. ### Competing Interest Statement Hiram Gay receives honoraria from Boston Scientific. Ryan Jackson receives honoraria from Intuitive, Inc. Peter Oppelt receives research funding and salary support from Merck and HiFiBio. The remaining authors report no disclosures. ### Funding Statement This study did not receive any funding. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Human Research Protection Office Institutional Review Board of the Washington University School of Medicine gave ethical approval for this work (#202305057). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors