Differential dosimetric benefit of proton beam therapy over intensity modulated radiotherapy for a variety of targets in patients with intracranial germ cell tumors

Table 2 Dosimetric comparison and statistical analysis of PTV coverage

Item	PTV location	Median (range, min–max)			p value^*
Item	PTV location	IMRT	PSPT	SSPT	IMRT vs PSPT	IMRT vs SSPT	PSPT vs SSPT
PTV CI	WV	0.85 (0.72–0.88)	0.70 (0.69–0.71)	0.91 (0.89–0.92)	<0.05	<0.05	<0.05
	PG	0.92 (0.87–0.92)	0.83 (0.62–0.87)	0.94 (0.90–0.90)	<0.05	<0.05	<0.05
	SS	0.89 (0.88–0.92)	0.74 (0.72–0.83)	0.92 (0.90–0.94)	<0.05	<0.05	<0.05
	BG	0.88 (0.86–0.91)	0.80 (0.74–0.82)	0.94 (0.93–0.95)	<0.05	<0.05	<0.05
PTV GI	WV	3.30 (3.08–3.75)	1.90 (1.85–2.04)	2.12 (1.99–2.19)	<0.05	<0.05	<0.05
	PG	3.89 (3.47–4.62)	2.90 (2.50–3.25)	2.50 (2.36–3.34)	<0.05	<0.05	NS
	SS	3.82 (3.71–4.14)	2.78 (2.64–3.27)	2.59 (2.48–2.87)	<0.05	<0.05	NS
	BG	3.77 (3.46–4.23)	2.35 (2.18–2.57)	2.30 (2.23–2.60)	<0.05	<0.05	NS
PTV HI	WV	0.97 (0.96–0.98)	0.95 (0.94–0.95)	0.98 (0.98–0.98)	<0.05	<0.05	<0.05
	PG	0.96 (0.95–0.97)	0.97 (0.96–0.98)	0.98 (0.97–0.98)	NS	<0.05	NS
	SS	0.96 (0.95–0.97)	0.97 (0.96–0.98)	0.97 (0.95–0.98)	NS	NS	NS
	BG	0.97 (0.97–0.98)	0.97 (0.97–0.98)	0.97 (0.97–0.98)	NS	NS	<0.05
PTV PQI	WV	4.06 (3.82–4.73)	2.89 (2.75–3.11)	2.37 (2.23–2.46)	0.043	0.043	0.043
	PG	4.39 (3.92–5.55)	3.38 (3.12–5.47)	2.70 (2.54–3.83)	0.043	0.043	0.043
	SS	4.46 (4.26–4.88)	3.92 (3.62–4.05)	2.95 (2.88–3.12)	0.043	0.043	0.043
	BG	4.45 (4.00–4.93)	3.01 (2.81–3.59)	2.49 (2.44–2.86)	0.043	0.043	0.043

WV whole ventricle, PG pineal gland, SS suprasellar, BG basal ganglia, PTV planning target volume, CI conformity index, GI gradient index, HI homogeneity index, PQI plan quality index, IMRT intensity-modulated radiation therapy, PSPT passively scattered proton therapy, SSPT spot scanning proton therapy, NS not significant
^* p -value by Wilcoxon signed rank test

ISSN: 1748-717X