Imaging characteristics of nasopharyngeal carcinoma for predicting distant metastasis

To determine the imaging characteristics of nasopharyngeal carcinoma (NPC) that may be associated with increased risk of distant metastasis.

A total 164 patients with NPC were reviewed retrospectively. Patients were divided into the metastatic group (n=110) or the non-metastatic group (n=54). Non-metastatic was defined as no evidence of distant metastasis during at least 5 years of follow-up. Pretreatment images of the primary tumour and nodal involvement were analysed. Statistical analyses were performed to identify the factors that may predict distant metastasis.

The statistically significant sites of tumour extension in the metastatic group included: skull base bone (p<0.001), cervical spine (C-spine; p=0.012), parapharyngeal space (p=0.003), pterygopalatine fossae (PPF; p=0.004), prevertebral space (p<0.001), masticator space (p=0.006), carotid space (p=0.001), and intracranial extension (p=0.004). Statistically significant nodal involvement included bilateral involvement (p=0.04), size 3-6 cm (p=0.011), >10 pathological nodes (p<0.001), level IB (p=0.013), IIB (p=0.011), III (p=0.001), IV (p<0.001), VB (p=0.001), and supraclavicular (p=0.003) and intraparotid nodes (p=0.004). The mean number of significant involvement factors was significantly higher in the metastatic group (3.46±2.24 tumour extension sites and 5.04±2.51 nodal involvement factors) than in the non-metastatic group (p<0.001).

NPC patients with local extension at more than three sites and with more than five nodal involvement factors should be screened for distant metastasis.