Parotid Gland Stem Cell Preservation during Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma: Dosimetric Analysis and Feasibility

Table 4

Comparison of the parotid gland and its duct radiation doses between two intensity-modulated radiotherapy plans.

Organs at risk	Regular group (n = 35)	Restricted group (n = 45)	t
Left parotid gland
Dmean (Gy)	31.55 ± 0.77	31.32 ± 0.92	1.1896	0.2378
V20 (%)	78.77 ± 3.22	66.12 ± 3.81	15.7451	<0.0001
V30 (%)	43.26 ± 3.13	43.27 ± 3.55	0.0132	0.9895
V45 (%)	24.64 ± 2.72	26.87 ± 2.34	3.9378	0.0001
Left ducts
Dmean (Gy)	22.28 ± 1.33	15.38 ± 0.60	31.0195	<0.0001
V15 (%)	98.61 ± 0.30	39.11 ± 9.91	35.4573	<0.0001
V20 (%)	72.22 ± 9.47	2.47 ± 0.39	49.4449	<0.0001
V26 (%)	14.80 ± 5.46	0.14 ± 0.05	18.0435	<0.0001
Right parotid gland
Dmean (Gy)	31.03 ± 0.93	30.91 ± 0.97	0.5588	0.5778
V20 (%)	75.82 ± 4.64	61.75 ± 4.00	14.5498	<0.0001
V30 (%)	42.45 ± 3.73	42.61 ± 3.46	0.1983	0.8433
V45 (%)	22.69 ± 3.09	26.70 ± 3.11	5.7372	<0.0001
Right ducts
Dmean (Gy)	22.26 ± 1.27	14.86 ± 0.41	34.3638	<0.0001
V15 (%)	98.88 ± 0.74	37.47 ± 14.62	24.7901	<0.0001
V20 (%)	73.84 ± 16.69	1.85 ± 0.22	28.9848	<0.0001
V26 (%)	12.02 ± 5.16	0.10 ± 0.02	15.5248	<0.0001

The bold text means statistically significant.