Abstract
PurposeWe sought to define the locoregional extension patterns of nasopharyngeal carcinomas (NPCs) by positron emission tomography (PET)/magnetic resonance imaging (MRI) and to improve clinical target volume (CTV) delineation.MethodsBetween May 2017 and March 2021, 331 consecutive patients with nonmetastatic NPCs who underwent pretreatment, simultaneous whole-body PET/MRI for staging were included in this study.ResultsThe high-risk regions included the base of the sphenoid bone, the prestyloid compartment, prevertebral muscle, foramen lacerum, medial pterygoid plate, sphenoidal sinus, clivus, petrous apex, and foramen ovale. When the high-risk regions were invaded, the incidence rates of tumor invasion into the medium-risk regions increased. In contrast, when the high-risk regions were not involved, the incidence rates of tumor invasion into the medium-risk regions were mostly less than 10%, excluding the post-styloid compartment and oropharynx. According to the updated consensus guidelines of the neck node levels for head and neck tumors from 2013, level IIa (77.3%, 256/331), level IIb (75.8%, 251/331), and level VIIa (71.3%, 236/331) were the most frequently involved levels, followed by levels III (42.6%), Va (13.9%), IVa (8.8%), IVb (3.6%), Ib (3.6%), Vb (2.4%), VIIb (2.4%), VIII (1.8%), Vc (0.9%), and Xa (0.3%). Skip lymph node metastasis occurred in only 1.9% of patients.ConclusionsFor NPCs, primary disease and regional lymph node spread follow an orderly pattern, and a skip pattern of lymph node metastasis was unusual. Involved level radiotherapy might be feasible for cervical lymph node levels below the caudal border of cricoid cartilage and level VIIb.
Highlights
Radiotherapy is the primary treatment modality for nonmetastatic nasopharyngeal carcinomas (NPCs) [1]
Medical records and imaging studies were analyzed retrospectively, and all patients were staged according to the 8th edition of the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) staging system [8, 9]
The high-risk regions included the basis of the sphenoid bone, prestyloid compartment, prevertebral muscle, foramen lacerum, medial pterygoid plate, sphenoidal sinus, clivus, petrous apex, and foramen ovale
Summary
Radiotherapy is the primary treatment modality for nonmetastatic nasopharyngeal carcinomas (NPCs) [1]. Target delineation of NPCs is often challenging for the proximity of the tumors to critical organs at risk such as the brain stem and spinal cord. Based on the best available investigation methods, accurate delineation of the Gross Tumor Volume (GTV) is the first step. In the National Comprehensive Cancer Network (NCCN) guidelines, magnetic resonance imaging (MRI) with a contrast of skull base to clavicle is recommended for defining the locoregional extension of NPC, and 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is merely recommended for nodal and distant metastases in patients with multistation or lower neck nodal involvement or high-grade tumor histology [3]. The diagnostic criteria of lymph node involvement included lymph nodes with overt FDG uptake in the international guideline for target volume delineation of NPC [4]. With the development of PET/MR, the target volume delineation of NPCs should be reevaluated
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