Table 3.

Mean radiation dose as predictors of biomarker injury: linear-mixed-effects analysis of mean RT dose (Gy) as a predictor of volume, FA, and MD of each brain ROI, while controlling for time

Outcome	Brain Region	Estimate (β)*	Standard Error	P Value
Volume†	Total CC	−0.00760	−0.00402	.068
	Posterior CC	−0.00151	0.00127	.237
	Mid-Posterior CC	−0.00061	0.00052	.240
	Central CC	−0.00083	0.0005	.105
	Mid-Anterior CC	−0.00140	0.0006	.023
	Anterior CC	−0.00201	0.00134	.139
	Total IHWM	−0.0805	0.222	.718
	Right IHWM	−0.0854	0.068	.212
	Left IHWM	−0.0185	0.0615	.764
FA	Total CC	−0.0751	0.0334	.029‡
	Posterior CC	−0.1635	0.0346	< .001‡
	Mid-Posterior CC	−0.0375	0.0339	.273
	Central CC	−0.0164	0.0316	.605
	Mid-Anterior CC	−0.0045	0.0335	.893
	Anterior CC	−0.1046	0.0457	.026‡
	Total IHWM	−0.0274	0.0236	.250
	Right IHWM	−0.0179	0.0195	.362
	Left IHWM	−0.0173	0.0185	.352
MD	Total CC	0.000746	0.000553	.180
	Posterior CC	0.000722	0.000458	.120
	Mid-Posterior CC	0.000464	0.000447	.302
	Central CC	0.000597	0.000425	.163
	Mid-Anterior CC	0.000606	0.000544	.267
	Anterior CC	0.00185	0.000716	.012‡
	Total IHWM	0.000173	0.000536	.747
	Right IHWM	0.000244	0.000452	.589
	Left IHWM	0.000107	0.000432	.805

Abbreviations: CC = corpus callosum; FA = fractional anisotropy; IHWM = intrahemispheric white matter tracts; MD = mean diffusivity; ROI = region of interest; RT = radiation therapy.

Significant results (P < .05) are shown in bold.

^*β estimate units are Gy/(mo*cm³) for volume, Gy/mo for FA, and Gy/(mo*μm²/ms) for MD.

^†Volume models control for percentage of ROI censored.

^‡Results that remained significant after corrections for multiple comparisons.