Table 4.

Dosimetric parameters of organs at risk in esophageal carcinoma treated with photon vs. particle radiotherapy

OARs	Characteristics	Ling et al. (50.4 Gy) [9]					Takakusagi et al. (50.4 Gy) [35]
		Proton	IMRT	p	3DCRT	p	Carbon	VMAT	p	3DCRT	p
Spinal cord	Dmax (Gy)	11.6 ± 10.0	36.9 ± 3.5	0.001	31.2 ± 9.7	0.001	25.6 ± 3.5	41.3 ± 2.9	< 0.001	44.6 ± 0.6	< 0.001
Lungs	Dmean (Gy)	6.0 ± 2.6	9.5 ± 3.2	0.016	9.4 ± 4.0	0.040	1.8 ± 0.9	11.4 ± 2.3	< 0.001	5.3 ± 1.8	< 0.001
	V5 (%)	21.4 ± 10.3	46.9 ± 17.6	0.001	34.1 ± 13.9	0.032	8.4 ± 3.7	77.7 ± 17.8	< 0.001	21.6 ± 8.3	< 0.001
	V10 (%)	19.4 ± 8.6	37.8 ± 14.7	0.003	29.1 ± 12.7	0.060	6.7 ± 3.2	52.5 ± 12.1	< 0.001	14.8 ± 5.5	< 0.001
	V20 (%)	15.3 ± 6.5	16.2 ± 5.8	0.794	22.1 ± 10.8	0.114	2.6 ± 1.7	14.8 ± 5.5	< 0.001	7.7 ± 3.3	< 0.001
	V30 (%)	6.1 ± 2.9	6.6 ± 3.2	0.720	9.8 ± 5.1	0.067	1.4 ± 1.0	3.9 ± 2.3	< 0.001	5.5 ± 2.5	< 0.001
	V40 (%)	4.3 ± 2.1	3.5 ± 2.0	0.391	4.7 ± 2.9	0.682	0.3 ± 0.5	1.0 ± 0.9	0.001	2.2 ± 1.2	< 0.001
	V50 (%)	1.1 ± 1.0	1.6 ± 1.3	0.251	3.3 ± 2.1	0.008	0.0 ± 0.1	0.0 ± 0.1	0.157	0.1 ± 0.2	0.006
Heart	Dmean (Gy)	12.6 ± 3.9	28.5 ± 5.5	0.001	27.5 ± 5.2	0.001	9.6 ± 4.5	22.3 ± 9.0	< 0.001	29.1 ± 11.7	< 0.001
	V10 (%)	N/A	N/A	N/A	N/A	N/A	46.5 ± 21.0	99.6 ± 39.6	< 0.001	69.2 ± 28.1	< 0.001
	V20 (%)	N/A	N/A	N/A	N/A	N/A	9.8 ± 5.6	45.0 ± 24.1	< 0.001	61.4 ± 25.8	< 0.001
	V30 (%)	20.9 ± 7.1	42.3 ± 15.3	0.001	32.7 ± 9.4	0.005	6.7 ± 3.7	18.0 ± 9.6	< 0.001	57.3 ± 24.8	< 0.001
	V40 (%)	16.2 ± 6.4	25.5 ± 11.0	0.036	25.8 ± 8.8	0.012	4.8 ± 2.6	7.3 ± 5.0	< 0.001	51.1 ± 23.5	0.001
	V50 (%)	2.8 ± 2.3	12.0 ± 8.6	0.008	20.0 ± 12.6	0.002	0.9 ± 0.6	1.1 ± 1.0	0.068	8.3 ± 6.6	0.006

Doses are presented as the RBE (relative biological effectiveness)-weighted dose

Abbreviations: OARs, organs at risk; D_max, maximum dose; D_mean, mean dose; IMRT, intensity-modulated radiotherapy; 3DCRT, 3D conformal radiotherapy; VMAT, volumetric modulated arc therapy; Vx, the percentage volume of the organs at risk receiving ≥ x Gy of irradiation; N/A, not available