Non-coplanar volumetric-modulated arc therapy (VMAT) for craniopharyngiomas reduces radiation doses to the bilateral hippocampus: a planning study comparing dynamic conformal arc therapy, coplanar VMAT, and non-coplanar VMAT

Table 2 Summary of doses delivered to the hippocampus and normal brain, in Gy

Structure/index	DCAT	coVMAT	ncVMAT	P-value (ANOVA)	P-value (DCAT vs. coVMAT)	P-value (DCAT vs. ncVMAT)	P-value (coVMAT vs. ncVMAT)
Structure/index	(Mean ± SD)			P-value (ANOVA)	P-value (DCAT vs. coVMAT)	P-value (DCAT vs. ncVMAT)	P-value (coVMAT vs. ncVMAT)
Bilateral Hippo
D2%	36.5 ± 11.2	29.5 ± 12.6	23.1 ± 15.5	0.095
Mean dose	20.7 ± 7.6	15.4 ± 8.1	10.7 ± 8.2	<0.05	0.515	<0.05	0.530
D40%_hippo	21.7 ± 8.4	16.2 ± 7.6	10.3 ± 7.9	<0.05	0.406	<0.05	0.326
EQD₂(40%_hippo)	15.5 ± 7.9	10.8 ± 6.3	6.5 ± 6.0	<0.05	0.41	<0.05	0.51
NV_D40%_hippo	1	0.7 ± 0.2	0.4 ± 0.2	<0.05	<0.05	<0.05	<0.05
Normal brain
Mean dose	6.8 ± 1.7	6.2 ± 1.5	6.8 ± 1.4	0.563

If a significant difference was evident when data from the entire cohort were compared via two-way analysis of variance (ANOVA), the Bonferroni post hoc test was performed to compare pairs of modalities
DCAT dynamic conformal arc therapy, coVMAT coplanar volumetric-modulated arc therapy, ncVMAT non-coplanar volumetric-modulated arc therapy, SD standard deviation, Hippo hippocampus
D2% dose to 2 % of the volume, D40% _hippo dose to 40 % of the volume of the bilateral hippocampus
EQD ₂ (40% _hippo ) equivalent dose in 2-Gy fractions (assuming α/β = 2) to 40 % of volume of the bilateral hippocampus
NV_D40% _hippo normalized value of D40%_hippo (the DCAT value was set to unity). The normalized values for coVMAT and ncVMAT were calculated as D40%_hippo(coVMAT)/D40%_hippo(DCAT) and D40%_hippo(ncVMAT)/D40%_hippo(DCAT), respectively

ISSN: 1748-717X