Visible lymph node irradiation (VNRT) of the low-risk neck levels inpatients with nasopharyngeal carcinoma: An exploratory trial protocol

Abstract Background The long-term complications in nasopharyngeal carcinoma (NPC) caused by radiotherapy can be decreased by reducing the volume of neck irradiation. We are proposing a new approach of neck prophylactic irradiation based on selective upper-neck irradiation, called VNRT (visible lymph node (LN) irradiation of the low-risk neck levels). Visible LNs are defined as any LN that doesn’t fulfill the diagnostic criteria for positive LNs but is greater than or equal to 3 mm in maximum diameter. The purpose of this study is to evaluate the efficacy and safety of VNRT in NPC. Methods In this exploratory trial, 20 patients will be included with histologically proven T1-3N0-1 NPC. Our proposed VNRT will include two clinical target volumes (CTVs) for the neck: LN levels of prophylactic irradiation (CTVln) and all visible LNs (CTVnd). For N0 patients and N1 patients who only have ipsilateral or bilateral positive retropharyngeal LNs, the CTVln will include bilateral level II, and the CTVnd will include all visible LNs in bilateral levels III and Va. For N1 patients who have positive LNs in neck level II, the CTVln will include bilateral level II and ipsilateral levels III and Va. Additionally, for these patients, the CTVnd will include all visible LNs located in ipsilateral levels IV and Vb and contralateral levels III and Va. For N1 patients who have positive LNs in neck levels II and III, the CTVln will include bilateral level II and ipsilateral levels III, IV, and V. The CTVnd for these patients will include all visible LNs located contralateral III and Va. The main study endpoint is 2-year regional relapse-free survival. Discussion This trial will explore visible lymph node irradiation(VNRT) of the low-risk levels in patients with NPC .And this novel treatment will significantly reduce the volume of neck irradiation and dose in organs at risk ,thus reducing radiation related long-term toxicities.And our study might provide a deeper understanding of the lymph node metastasis in NPC. Trial registration: This trial was registered in the China clinical trial registration center (Registration number: ChiCTR2300067783).