Prognostic influence of prevertebral space involvement in nasopharyngeal carcinoma: A retrospective study.

ABSTRACT

PURPOSE: To evaluate how prevertebral space involvement (PSI) and degree of tumor extension within the space affects prognosis in nasopharyngeal carcinoma (NPC). PARTICIPANTS AND METHODS: Data of patients with newly-diagnosed nonmetastatic NPC (n = 757) were retrospectively analyzed. Patients were separated into groups according to presence or absence of PSI and degree of tumor spread. Overall survival (OS), failure-free survival (FFS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS) were compared between the groups. RESULTS: Prevalence of PSI, simple prevertebral muscle involvement (PMI), and behind prevertebral muscle involvement (BPMI) were 44.9% (340/757), 22.5% (170/757), and 22.5% (170/757), respectively. OS, FFS, LRFS, and DMFS for patients with and without PSI were 64% vs. 84.8%, 68% vs. 85.6%, 85.8% vs. 94.4%, and 78.5% vs. 92.8%, respectively (all P < 0.001). PSI was an independent predictor of OS, FFS, LRFS, and DMFS. OS, FFS, and DMFS for patients with simple PMI and with BPMI were 72.7% vs. 54.8% (P = 0.002), 75.8% vs. 59.8% (P = 0.003), and 85.5% vs. 71.2% (P = 0.002), respectively. Degree of PSI extension was related to OS, FFS, and DMFS. OS, FFS, LRFS, and DMFS were significantly poorer in patients with PSI in T2-3 stage than in patients without PSI in T3 stage (P < 0.05), but comparable to those in patients with T4 stage (P > 0.05). CONCLUSIONS: PSI predicts poor prognosis in NPC. Survival is poorer in patients with BPMI than in those with simple PMI. NPC with PSI should be classified as T4 stage.