Optimization of Cervical Nodal CTV for Early and Medium Stage NPC

Optimization of Cervical Nodal Clinical Tumor Volume for Early and Medium Stage Nasopharyngeal Carcinoma: a Multicenter Non-inferior Randomized Controlled Phase III Clinical Trial

Current radiotherapy guidelines and consensus statements uniformly recommend elective region irradiation (ERI) as the standard strategy for nasopharyngeal carcinoma (NPC). However, given the scarcity of skip-metastasis, the improved assessment accuracy of nodal involvement, and the striking advancements in chemotherapy for NPC, a one-fits-all delineation scheme for clinical target volumes for the nodal region (CTVn) may not be appropriate anymore, and modifications of the CTVn delineation strategy may be warranted. Involved site irradiation (ISI) covering merely the initially involved nodal site and potential extranodal extension has been confirmed to be as effective as ERI with decreased radiation-related toxicities in some malignancies, but has not yet been investigated in NPC. This study aims to compare the regional control, survival outcomes, radiation-related toxicities, and quality of life (QoL) of ISI with conventional ERI in NPC patients with a limited nodal burden.

ISRT-NPC is a prospective, multicenter, open-label, noninferiority, phase III randomized controlled trial. A total of 488 patients will be randomly assigned in a 1:1 ratio to receive ISI or ERI. Randomization will be stratified by institution and N stage. Generally, in the ISI group, the high-risk CTV1 (dose: 60 Gy) includes a 1-cm expansion of the positive LN as well as the VIIa and the retrostyloid space above the bilateral transverse process of the atlantoaxial spine (C1), regardless of N status. The low-risk CTV2 (Dose: 50 Gy) covers the cervical nodal region with a 3-cm caudal expansion below the transverse process of C1 for N0 disease and a 3-cm expansion below the positive LN for positive LNs (at least covering the level II).

1. Age between 18 and 75 years;
2. Karnofsky performance status (KPS) score ≥ 70;
3. Pathologically confirmed World Health Organization (WHO) type II-III NPC;
4. TNM stage I-III (T1-3N0-2M0) according to the 8th American Joint Committee on Cancer / Union for International Cancer Control (AJCC/UICC) staging system with a maximum diameter (MAD) of cervical involved LNs ≤ 3 cm, namely LB-LN;
5. Available baseline nasopharynx and neck computed tomography (CT) or magnetic resonance imaging (MRI) (strongly advocated) data (including functional MRI sequences) and measurable tumor lesions;
6. All procedures for defining the tumor burden completed within 4 weeks of registration;
7. Survival expectancy of at least 6 months;
8. Normal marrow and organ function: hemoglobin ≥ 120 g/L, WBCs ≥ 4 × 109 /L, platelets ≥ 100 × 109 /L; liver and kidney function-related indicators within 1.25*the normal upper limit;
9. Patient willingness to comply with the protocol;
10. Patient willingness and ability to provide an informed consent form.