Prognostic value of prepontine cistern invasion in nasopharyngeal carcinoma treated by intensity-modulated radiotherapy

Objectives: To investigate the prognostic value of prepontine cistern invasion (PPCI) in nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiotherapy (IMRT). Materials and methods: Five hundred and four non-disseminated NPC patients who underwent magnetic resonance imaging examination before radical IMRT between November 2000 and December 2008 were retrospectively reviewed. The diagnostic criteria for PPCI were tumor invasion through the posterior cortex of clivus and extension into the prepontine cistern. Results: The median follow-up of the patients in this study was 63.5 months. PPCI was found in 44 patients (25% of T4 patients). The 5-year progression-free survival (PFS), local control (LC), distant metastasis-free survival (DMFS), and overall survival (OS) of all patients, with and without PPCI, were 44.3% and 70.5% (p < 0.001), 84.4% and 89.1% (p = 0.376), 66.6% and 87.3% (p < 0.001), and 59.6% and 80.2% (p < 0.001), respectively. In T4 patients with PPCI and without PPCI, the 5-year PFS, LC, DMFS, and OS were 44.3% and 62.5% (p = 0.023), 84.4% and 84.9% (p = 0.946), 66.6% and 83.1% (p = 0.022), and 59.6% and 71.0% (p = 0.045), respectively. Using multivariate analysis, PPCI was found to be an independent poor prognostic factor for PFS (HR = 1.816; p = 0.007), DMFS (HR = 1.928; p = 0.045), and OS (HR = 1.798; p = 0.016). Conclusion: Prepontine cistern invasion was an independent prognostic factor for poor DMFS and OS but not LC in NPC patients treated with IMRT, even within T4 patients.