Table 2. Univariate analysis of clinical characteristics and local tumor extension of 717 patients with NPC.

Characteristic	HR	95% CI	P
GTV-p (<26.8 mL vs. ≥26.8 mL)	3.379	1.773-6.440	<0.001
Baseline LDH (<245 IU/L vs. ≥245 IU/L)	2.674	1.055-6.779	0.038
N category (N0-1 vs. N2-3)	2.108	1.134-3.918	0.018
Nasal cavity	2.154	1.197-3.879	0.011
Oropharynx	1.286	0.544-3.037	0.578
Masticator space	2.335	1.278-4.268	0.006
Prevertebral muscle	2.313	1.272-4.207	0.006
Parapharyngeal space	5.272	1.634-17.018	0.005
Pterygopalatine fossa	2.888	1.553-5.369	0.001
Pterygoid process	1.717	0.950-3.104	0.074
Base of sphenoid bone	2.145	1.174-3.921	0.013
Clivus	2.452	1.349-4.454	0.003
Petrous apex	1.720	0.958-3.088	0.069
Great wing of sphenoid bone	2.033	1.082-3.823	0.028
Foramen lacerum	2.583	1.428-4.671	0.002
Oval foramen	1.913	0.988-3.704	0.054
Hypoglossal canal	2.817	1.394-5.693	0.004
Jugular foramen	4.045	1.712-9.556	0.001
Foramen magnum	4.234	2.047-8.758	<0.001
Ethmoid sinus	4.222	1.885-9.458	<0.001
Sphenoid sinus	2.261	1.187-4.309	0.013
Maxillary sinus	7.015	2.172-22.653	0.001
Orbit	4.043	1.804-9.060	0.001
Cervical spine	4.480	1.765-11.371	0.002
Cavernous sinus	2.730	1.468-5.077	0.002
Intracranial	4.068	1.816-9.112	0.001
Cluster 1with two or more anatomic sites involved	3.107	1.387-6.959	0.006
Cluster 2 with one or more anatomic sites involved	2.344	1.187-4.629	0.014
Cluster 3 with one or more anatomic sites involved	3.812	1.969-7.383	<0.001

HR, hazard ratio; CI, confidence interval; other abbreviations as in Table 1.