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Prognostic significance of the various classifications for parapharyngeal space involvement in nasopharyngeal carcinoma

Abstract Conclusion: Advanced parapharyngeal space (PPS) involvement showed stronger prognostic value than PPS involvement. The classification of PPS involvement proposed by Min or Sham was the most appropriate classification for parapharyngeal extension in nasopharyngeal carcinoma (NPC). The degree of tumor extension into the PPS should be considered in future TNM staging revisions. Objectives: This study was conducted to evaluate the prognostic significance of the various classifications for PPS involvement in patients with NPC. Methods: From January to July 2000, a total of 176 patients with pathologically diagnosed NPC were prospectively enrolled in this study. The extent of PPS involvement was examined by contrast-enhanced computed tomography (CT) scan and graded according to the four previously reported classifications (Min, Sham, Xiao, and Heng). Results: The incidence of PPS involvement was 81.8%. The 5-year overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and local relapse-free survival rates (LRFS) of the patients with and without PPS involvement were 68.1% and 90.2% (p = 0.010), 66.1% and 87.2% (p = 0.013), 76.7% and 93.6% (p = 0.032), and 84.9% and 93.1% (p = 0.220), respectively. Multivariate analysis showed that PPS involvement (yes vs no) was not an independent prognostic factor. However, graded PPS involvement was an independent factor affecting the prognosis of NPC. When the four classifications were included in a Cox model, it was shown that PPS involvement based on Min's classification was an independent factor for OS (p = 0.001). PPS involvement based on Sham's classification was an independent factor for PFS (p = 0.010) and DMFS (p = 0.009).