Abstract
Background
Parapharyngeal involvement (PI) is common in local invasion but with different degrees in nasopharyngeal carcinoma (NPC). This study firstly assessed the prognostic value of PI subclassifications divided by parapharyngeal muscles in NPC.
Methods
1,752 newly diagnosed NPC patients from two centers were enrolled. The involvement of parapharyngeal muscles including levator veli palatine muscle (LVPMI), tensor veli palatine muscle (TVPMI), medial pterygoid muscle (MPMI) and lateral pterygoid muscle (LPMI) was diagnosed by magnetic resonance imaging (MRI). Univariate and multivariate models were constructed to assess the association between PI and survival.
Results
The progression-free survival (PFS), overall survival (OS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS) between No-PI and LVPMI were similar, p values were 0.446, 0.337, 0.372 and 0.446, respectively, similar to PFS, OS, DMFS and LRRFS between MPMI and LPMI. So PI subclassifications were divided into four degrees: No-PI/LVPMI, TVPMI, MPMI/LPMI, and (infratemporal fossa involvement, IFI). The survival curves among four degrees were statistically different (p < 0.05), except for PFS, OS, and LRRFS between grade 3 and grade 4. Multivariate analyses indicated PI degree (grade 1/2 vs. grade 3/4) was an independent prognostic factor of PFS, OS, DMFS and LRRFS (p < 0.05). If MPMI/LPMI was classified into the T3 stage, there were only 0.6% (10/1,752) incidence rates changing in T2 or T3 stages, and the predictive value was without statistical difference (p > 0.05).
Conclusions
In NPC patients, it was feasible to divide PI by parapharyngeal muscles. The advanced PI predicted poorer survival outcomes than those with mild PI.