Abstract
BackgroundThe aim of this study was to investigate the prognostic significance and various classifications for anatomic masticator space involvement (MSI) in patients with nasopharyngeal carcinoma (NPC).MethodsThis study retrospectively analyzed 742 patients with untreated nondisseminated NPC who underwent magnetic resonance imaging (MRI) scan of the nasopharynx and neck. The MSI was graded according to different anatomic features. The overall survival (OS), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) of the patients with different MSI grades were analyzed using the Kaplan-Meier method and log-rank tests.ResultsThe frequency of MSI was 24.1% (179/742). The 5-year OS, LRFS, DMFS, DFS for NPC patients with versus without MSI were 70.9% versus 82.5% (P = 0.001), 94.1% versus 91.4% (P = 0.511), 81.4% versus 88.7% (P = 0.021), and 78.0% versus 83.5% (P = 0.215), respectively. Significant differences in OS were also found among different MSI groups. In the patients with MSI, the OS of the group with medial and/or lateral pterygoid involvement (MLPI) NPC was 73.9% compared to 51.3% (P < 0.0001) in the patients with infratemporal fossa involvement (IFI).ConclusionsMSI was an independent prognostic factor for OS and DMFS. NPCs invading the masticator space should be separately categorized into MLPI and IFI prognostic groups. We suggest that MLPI should be staged as T3 while IFI is staged as T4 disease in future TNM staging revision.
Highlights
The aim of this study was to investigate the prognostic significance and various classifications for anatomic masticator space involvement (MSI) in patients with nasopharyngeal carcinoma (NPC)
The analyses revealed that classification patterns A, B and C showed MSI grade was an independent prognostic factor for overall survival (OS) (P < 0.041 in pattern A, P = 0.018 in pattern B, P = 0.007 in pattern C), but not for local relapse-free survival (LRFS), distant metastasis-free survival (DMFS) and disease-free survival (DFS)
Involvement of medial/lateral pterygoid muscle only should be classified as T3, and infratemporal fossa involvement should be classified as T4 Based on our results, we propose that IFI should be separated from medial and/or lateral pterygoid involvement (MLPI) and be classified into a higher T stage
Summary
The aim of this study was to investigate the prognostic significance and various classifications for anatomic masticator space involvement (MSI) in patients with nasopharyngeal carcinoma (NPC). Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors in southern China and Southeast Asia with incidences reported as 15-50 per 100,000 in high-incidence areas [1,2,3,4,5,6,7]. NPC is an aggressive disease and tends to involve surrounding tissues and organs. The masticator space is one mandible, whereas the superior limit is the base of the skull [8,9]. The masticator space plays an important role in the tumor staging system of NPC. Radiology textbooks often use the same definition of “masticator space” with inclusion of the medial and lateral pterygoid muscles [11]
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