Table 3. Comparison of tumor invasion in adjacent regions between pNPC and rNPC.

Tumor invasion site	Invasion in pNPC and rNPC (number)	Invasion in pNPC alone (number)	Invasion in rNPC alone (number)	No invasion in pNPC or rNPC (number)	P
Nasopharynx	29	8	0	0	0.008
Oropharynx	1	2	0	34	0.500
Nasal cavity	4	5	3	25	0.727
Parapharyngeal space	10	22	0	5	<0.001
Skull base	19	9	2	7	0.065
Paranasal sinus	5	5	6	21	1.000
Intracranial cavity	7	4	2	24	0.687
Infratemporal fossa	1	2	0	34	0.500
Laryngopharynx	0	0	1	36	1.000
Orbital apex	0	2	1	34	1.000
Masticatory muscles	1	7	2	27	0.180

Abbreviation: pNPC=primary nasopharyngeal carcinoma, rNPC= recurrent nasopharyngeal carcinoma