Single arc volumetric-modulated arc therapy is sufficient for nasopharyngeal carcinoma: a dosimetric comparison with dual arc VMAT and dynamic MLC and step-and-shoot intensity-modulated radiotherapy

Table 2 Comparison of target volume homogeneity and conformity in all four radiotherapy plan groups

		VMAT1	VMAT2	dIMRT	ssIMRT	p _GLM-u	p _VMAT1	p _VMAT1	p _VMAT1	p _VMAT2	p _VMAT2	p _dIMRT
							_-VMAT2	_-dIMRT	_-ssIMRT	_-dIMRT	_-ssIMRT	_-ssIMRT
PTV_72.6	HI	0.07 ± 0.01	0.07 ± 0.01	0.09 ± 0.01	0.09 ± 0.01	<0.001	0.510	<0.001	<0.001	<0.001	<0.001	0.653
	CI	0.57 ± 0.09	0.57 ± 0.08	0.49 ± 0.07	0.50 ± 0.07	<0.001	0.955	<0.001	<0.001	<0.001	<0.001	0.355
	D2%	75.43 ± 0.76	75.40 ± 0.89	76.30 ± 0.86	76.57 ± 0.66	0.472
	D50%	72.64 ± 0.03	72.68 ± 0.03	72.93 ± 0.11	72.80 ± 0.10	0.588
	D95%	70.55 ± 0.24	70.69 ± 0.30	70.18 ± 0.17	70.10 ± 0.23	0.464
	D98%	70.01 ± 0.45	70.15 ± 0.57	70.01 ± 0.44	70.02 ± 0.40	0.742
PTV_63.6	HI	0.21 ± 0.02	0.21 ± 0.02	0.23 ± 0.02	0.23 ± 0.02	<0.001	0.427	<0.001	<0.001	<0.001	<0.001	0.614
PTV_63.6	CI	0.76 ± 0.03	0.76 ± 0.04	0.73 ± 0.03	0.73 ± 0.04	0.001	0.448	0.003	0.001	<0.001	<0.001	0.605
	D2%	72.45 ± 1.11	72.42 ± 1.26	72.89 ± 1.16	73.20 ± 0.79	0.005	0.904	0.174	0.003	0.157	0.002	0.204
	D50%	64.14 ± 0.28	63.64 ± 0.11	63.99 ± 0.19	63.83 ± 0.17	0.236
	D95%	60.42 ± 0.18	60.44 ± 0.12	60.20 ± 0.17	60.17 ± 0.27	0.715
	D98%	58.49 ± 0.32	58.83 ± 0.39	57.99 ± 0.50	58.55 ± 0.41	<0.001	0.007	<0.001	0.651	<0.001	0.021	<0.001

HI: homogeneity index; CI: conformity index; GLM-u: general linear model-univariate; VMAT1: single arc VMAT, VMAT2: dual arc VMAT; dIMRT: dynamic MLC IMRT; ssIMRT: step-and-shoot IMRT. “Bold numbers” means that p value has a statistically significance.

ISSN: 1748-717X