Patients

This retrospective study was approved by the institutional ethics committee and the need for informed consent was waived. All the methods were carried out in accordance with the approved guidelines. We retrospectively reviewed the medical records of consecutive 1811 patients with previously untreated, biopsy-proven NPC with positive cervical node metastasis and no distant metastasis that was treated with IMRT between November 2009 and February 2012 at our Cancer Center. Among these 1811 patients, 308 without cervical node metastasis and 80 without pretreatment MRI scans of the neck and nasopharynx were excluded. Eventually, a total of 1423 NPC patients were enrolled in our study.

The routine staging work-up included a complete medical history and clinical examination; direct fiberoptic nasopharyngoscopy, hematology, and biochemistry profiles; MRI of the nasopharynx and whole neck; chest radiography; whole body bone scanning; and abdominal sonography. All patients were restaged according to the 7th edition of the International Union against Cancer/American Joint Committee on Cancer (UICC/AJCC) system ²⁷. The clinical characteristics of the patients before treatment are listed in Table ​Table11.

Incidence of cervical node necrosis (CNN) at specific nodal levels in 1423 patients with nasopharyngeal carcinoma (NPC)

*The grading criteria for CNN were as follows: grade 0 CNN, no hypodense zones; grade 1 CNN, ≤ 33% nodal areas showing hypodense zones; and grade 2, >33% nodal areas showing hypodense zones.

^&Nodal levels were assigned according to the 2013 International Consensus Guidelines.