Distant metastases in head and neck carcinoma: Identification of prognostic groups with MR imaging

Purpose: To evaluate retrospectively the prognostic significance of lymph node parameters assessed on pretreatment magnetic resonance (MR) images for development of distant metastases in patients with head and neck squamous cell carcinomas. Materials and methods: Pretreatment MR images of 311 patients were retrospectively reviewed for the presence of lymph nodes at specific neck node levels as well as the size and the presence of a number of lymph node characteristics including extranodal spread, central necrosis and number and volume of ipsi- and contralateral nodes. Of these patients, 174 (56%) had MRI-positive nodes (defined as nodes with minimum axial diameter >8 and >4 mm for paratracheal level and retropharyngeal nodes). Results: The 2-year distant-metastasis free survival rate (DMFSR) for patients without MRI-positive nodes was 94% compared to 75% for those patients with MRI-positive nodes. In patients with MRI-positive nodes, results of multivariate analysis with the Cox regression model yielded statistical significance for presence of extranodal spread (ENS), detected on MRI, as the only independent prognostic factor associated with the 2-year DMFSR (p = 0.002). Based on the analysis, three risk groups regarding the DMFSR could be identified. Low-risk group (DMFSR:94%) consisted of patients without MRI-positive nodes. Intermediate-risk group (DMFSR:81%) consisted of patients with MRI-positive nodes without ENS. High-risk group (DMFSR:59%) consisted of patients with MRI-positive nodes and ENS as shown on MRI (p < 0.0001). Statistical separation for different tumor locations showed MRI-determined ENS (larynx: p = 0.05; oropharynx: p = 0.04; oral cavity: p < 0.001), lowjugular/posterior triangle nodes (oropharynx: p = 0.02), paratracheal nodes (larynx: p = 0.03), and contralateral node volume >5 cm³ (larynx: p = 0.03; oral cavity: p = 0.02) to be significant predictors with regard to DMFSR. Conclusion: Especially patients with on MRI demonstrating extranodal spread and with suspicious nodes at lowjugular/posterior triangle (oropharyngeal cancer) or paratracheal level (laryngeal cancer), or with contralateral enlarged nodes (laryngeal and oral cavity cancer) are at high risk for developing distant metastases and this subset of patients might benefit from supplementary imaging screening (CT-chest, PET-scan).