Table 2.

Receiver operating characteristic analysis for Q, V, and combined Q/V logistic regression models to predict RILT incidence

Structure	Metric	Area under the curve	95% Confidence interval
Lungs-GTV	V20, %	0.69–	0.55–0.82
	Q iV20, a.u.	0.67–	0.54–0.79
	V iV20, a.u.	0.68–	0.56–0.81
	Low-functioning Q + V receiving ≥20 Gy, %	0.76–	0.65–0.87
	ADL, Gy∗	0.65–	0.52–0.78
	Low Q/V ≥20, %∗
Ipsilateral lung-GTV	V20, %	0.74–	0.62–0.85
	Q iV20, a.u.	0.7–	0.58–0.82
	V iV20, a.u.	0.74–	0.63–0.85
	Low-functioning Q + V receiving ≥20 Gy, %	0.79–	0.65–0.87
	ADL, Gy∗	0.75–	0.63–0.87
	Low Q/V ≥20, %∗
Contralateral lung-GTV	V20, %	0.35–	0.21–0.48
	Q iV20, a.u.	0.33–	0.18–0.49
	V iV20, a.u.	0.34–	0.18–0.51
	Low-functioning Q + V receiving ≥20 Gy, %	0.37–	0.22–0.52
	ADL, Gy∗	0.31–	0.14–0.48
	Low Q/V ≥20, %∗

Abbreviations: ADL = average dose to lower region of lung structure in Gy; GTV = gross tumor volume; iV₂₀ = average normalized functional intensity receiving ≥20 Gy in arbitrary units; low Q/V ≥20 = Q/V low-function volume, defined as the intersection between low-function Q and low-function V, that received ≥20 Gy as a percent of the total lung structure volume; Q = perfusion; V = ventilation; V₂₀ = volume of lung structure receiving ≥20 Gy as a percent of the total lung structure volume.

^∗Multivariate logistic regression model.