Omitting Elective Irradiation of the Contralateral Retropharyngeal Nodes in Oropharyngeal Squamous Cell Carcinoma Treated with Intensity-modulated Radiotherapy.

Moeko Nagatsuka,Ryan T Hughes,Rachel F Shenker,Bart A Frizzell,Kathryn M Greven

doi:10.7759/cureus.3825

Abstract

Introduction: The use of intensity-modulated radiation therapy (IMRT) in head and neck cancers has allowed for selective sparing of low-risk or uninvolved lymph nodes. In oropharyngeal cancers, the benefits and risks of omitting contralateral retropharyngeal lymph nodes (RPLN) remain uncertain. This study examines the outcomes of elective coverage of contralateral RPLN in oropharyngeal cancer treated with definitive IMRT.Methods: We analyzed 54 patients with newly diagnosed unilateral tonsil or base of tongue squamous cell carcinoma with at most unilateral neck involvement (cN0-N2b) and no RPLN involvement. These patients had no prior head and neck irradiation and were treated with definitive radiotherapy or chemoradiotherapy between 2012 and 2017. Cumulative incidences of local/regional/distant failure were estimated using competing risks methodology, and overall survival (OS) was estimated using the Kaplan-Meier method.Results: All patients received elective nodal coverage to the ipsilateral RPLN, and 38 (62%) patients did not receive elective treatment of the contralateral RPLN. There were no significant differences in baseline characteristics. There were no contralateral RPLN failures observed. When comparing patients who received contralateral RP treatment with those who did not, there were no significant differences in two-year local failure (23% vs. 9%, p = 0.09), regional failure (18% vs. 4%, p = 0.12), or distant failure (15% vs. 9%, p = 0.62). Two-year OS was 89%. Mean parotid dose was not significantly lower after sparing vs. treating the contralateral RPLN (median 25.6 vs. 32.7 Gy, p = 0.15).Conclusions: The omission of contralateral RPLN irradiation in tonsil or tongue base carcinomas with unilateral neck involvement is safe without compromising disease control.

Highlights

The use of intensity-modulated radiation therapy (IMRT) in head and neck cancers has allowed for selective sparing of low-risk or uninvolved lymph nodes
The purpose of this study is to examine the outcomes of elective coverage of the contralateral retropharyngeal lymph nodes (RPLN) in patients with oropharyngeal carcinoma with at most unilateral neck involvement of treated with definitive IMRT
This work was approved by the Institutional Review Board of Wake Forest University (IRB00047017), which permitted waiver of consent due to the retrospective nature of this study and the minimal risk to patients

Summary

Introduction

The use of intensity-modulated radiation therapy (IMRT) in head and neck cancers has allowed for selective sparing of low-risk or uninvolved lymph nodes. The retropharyngeal lymph nodes (RPLN) were first classified by Henri Rouviere in 1932 and are classified as part of level VIIa of the prevertebral compartment group [4] This region is considered to have high rates of nodal metastasis from primary head and neck cancer, such as oropharyngeal (up to 20%-50% of soft palate or posterior pharyngeal wall), nasopharyngeal (up to 40%-90%), and hypopharyngeal cancers (up to 18%57%), to warrant elective or therapeutic treatment [5]. While inclusion of the RPLN as IMRT targets in oropharyngeal cancer cases has been recommended [6], other studies [7,8] have shown that for patients with unilateral HNSCC, sparing the contralateral RPLN (the clinically uninvolved side of the neck) is associated with minimal risk of failure in these regions and resulted in greater quality of life

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