Table 2. Rates of tumor invasion into anatomic sites surrounding the nasopharynx.
| Anatomic site | No. of patients (%) |
| High-risk | |
| Tensor veli palatine muscle | 1570 (66.4) |
| Nasal cavity | 1224 (51.7) |
| Basis of sphenoid bone | 1105 (46.7) |
| Pterygoid process | 1063 (44.9) |
| Clivus | 934 (39.5) |
| Petrous apex | 932 (39.4) |
| Prevertebral muscle | 876 (37.0) |
| Foramen lacerum | 826 (34.9) |
| Medium-risk | |
| Foramen ovale | 557 (23.5) |
| Great wing of sphenoid bone | 554 (23.4) |
| Oropharynx | 509 (21.5) |
| Medial pterygoid muscle | 449 (19.0) |
| Cavernous sinus | 424 (17.9) |
| Pterygopalatine fossa | 407 (17.2) |
| Sphenoidal sinus | 374 (15.8) |
| Hypoglossal canal | 256 (10.8) |
| Lateral pterygoid muscle | 219 (9.3) |
| Ethmoid sinus | 124 (5.2) |
| Jugular foramen | 120 (5.1) |
| Low-risk | |
| Orbit | 93 (3.9) |
| Infratemporal fossa | 73 (3.1) |
| Cervical vertebrae | 54 (2.3) |
| Maxillary sinus | 51 (2.2) |
| Hypopharynx | 21 (0.9) |
| Frontal sinus | 5 (0.2) |