Prognostic Value of Classifying Parapharyngeal Extension in Nasopharyngeal Carcinoma Based on Magnetic Resonance Imaging

Table 3

Characteristics for 1504 patients with different grades of parapharyngeal extension.

Characteristic	Number of patients
	G1	G2	G3	G4
Gender
Male	171	500	202	45	0.203
Female	57	182	51	18
Age
<50 y	144	464	163	39	0.419
≥50 y	84	218	90	24
N classification
N0	39	153	43	8	0.085
N1	139	414	171	42
N2-3	50	115	39	13
Radiation technique
Conventional technique	120	361	139	31	0.289
IMRT	94	292	104	25
3DCRT	14	29	10	7

3DCRT: three-dimensional conformal radiotherapy; IMRT: intensity-modulated radiation therapy; G1: mild parapharyngeal extension; G2: T3 without extensive parapharyngeal extension; G3: all T4 (excluding patients staged as T4 because of masticator space invasion); G4: extensive parapharyngeal extension.