Table 5.

Analysis of Prognostic Factors for Distant Metastasis-Free Survival

Variables	3-year distant metastasis-free survival (%)	P-value
		Univariate	Multivariate
RT technique
IMRT vs. 3D-CRT	81.9 vs. 77.1	0.656	0.275
Age (years)
<50 vs. ≥50	73.3 vs. 83.9	0.334	0.270
Gender
Male vs. female	81.4 vs. 71.4	0.433	0.375
Smoking status
Current or previous vs. never	79.4 vs. 77.8	0.769
Alcohol status
Current or previous vs. never	72.8 vs. 100	0.142	0.442
WHO histologya
1 vs. 2-3	74.1 vs. 82.9	0.558
T stage
1-2 vs. 3-4	85.7 vs. 73.3	0.435	0.417
N stage
0-1 vs. 2-3	81.9 vs. 72.9	0.627
AJCC stage
3 vs. 4	80.4 vs. 78.8	0.798
GTV (cc)
≤55 vs. >55	83.9 vs. 76.6	0.594
Total dose (BED, Gy10)
≤82.5 vs. >82.5	59.6 vs. 100	0.008	0.197
Daily dose (Gy)
≤2 vs. >2	64.8 vs. 85.6	0.142	0.040
RT duration (weeks)
≤7.5 vs. >7.5	80.2 vs. 79.4	0.945
RT interruption
Yes vs. no	71.6 vs. 84.0	0.512
Induction chemotherapy
Yes vs. no	78.6 vs. 80.1	0.762

RT, radiotherapy; IMRT, intensity-modulated radiotherapy; 3D-CRT, 3-dimensional conformal radiotherapy; WHO, World Health Organization; AJCC, American Joint Committee on Cancer Staging; GTV, gross tumor volume; BED, biologically equivalent dose.

^aWHO histology I, keratinizing squamous cell carcinoma; II, non-keratinizing carcinoma, differentiated type; III, non-keratinizing carcinoma, undifferentiated type