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

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.