Individualized elective irradiation of the clinically node‐negative neck in definitive radiotherapy for head and neck squamous cell carcinoma

BACKGROUND: Oral cavity (OC), oropharyngeal (OP), hypopharyngeal (HP), and laryngeal (LA) squamous cell carcinoma (SCC) have a high incidence of regional lymph node metastasis (LNM). Elective irradiation for clinically node‐negative neck is routinely administered to treat lymph nodes harboring occult metastasis. However, the optimal elective irradiation schemes are still inconclusive. In this study, we aimed to establish individualized elective irradiation schemes for the ipsilateral and contralateral node‐negative neck of these four types of cancer. METHODS: From July 2005 to December 2018, 793 patients with OC‐SCC, 464 with OP‐SCC, 413 with HP‐SCC, and 645 with LA‐SCC were recruited retrospectively. Based on the actual incidence of LNM and the tumor characteristics, risk factors for contralateral LNM, as well as node level coverage schemes for elective irradiation, were determined using logistic regression analysis. Additionally, we developed a publicly available online tool to facilitate the widespread clinical use of these schemes. RESULTS: For the ipsilateral node‐negative neck, elective irradiation at levels I‐III for OC‐SCC and levels II‐IVa for OP‐, HP‐ and LA‐SCC are generally recommended. In addition, level VIIa should be included in patients with OP‐SCC. Multivariate analyses revealed that posterior hypopharyngeal wall and post‐cricoid region involvement were independently associated with level VIIa metastasis in HP‐SCC (all P < 0.05). For the contralateral node‐negative neck, multivariate analyses revealed that ipsilateral N2b2‐N3, tumors with body midline involvement, and degree of tumor invasion were the independent factors for contralateral LNM (all P < 0.05). In patients who require contralateral neck irradiation, levels I‐II are recommended for OC‐SCC, and additional level III is recommended for patients with ipsilateral N3 disease. Levels II‐III are recommended for OP‐, HP‐, and LA‐SCC, and additional level IVa is recommended for patients with advanced T or ipsilateral N classifications. Furthermore, additional level VIIa is recommended only for OP‐SCC with T4 and ipsilateral N3 disease. CONCLUSION: Based on our findings, we suggest that individualized and computer‐aided elective irradiation schemes could reduce irradiation volumes in OC‐, OP‐ and HP‐SCC patients, as compared to current guidelines, and could thus positively impact the patients' quality of life after radiotherapy.