Table 3.

Results of multicollinearity diagnostics

Variables	Tolerance	VIF
Gender (female vs. male)	0.94	1.07
Clinical stage (I vs. II vs. III vs. IV)	0.72	1.40
GTV volume	0.08	12.85
PTV volume	0.09	10.60
MD	0.10	10.47
ED	0.05	20.32
LCR	0.87	1.15
BEDPTVmax (≧ 105.6 vs. < 105.6)	0.51	1.95
Fractional dose	0.42	2.37
Duration	0.46	2.20

VIF variance inflation factor, GTV gross target volume, PTV Planning target volume, MD maximum diameter for the tumor, ED equivalent diameter for the tumor, LCR lymphocyte ratio, BEDPTV_max the maximum dose in PTV recorded as BED