Table 5.

Cox proportional hazards regression analysis for time to radiation pneumonitis symptoms (N = 100)

Predictor	Coefficient	SE	Hazard ratio (95% CI)	p-value
SUV95a	0.18	0.057	1.2 (1.1-1.3)	<0.002
Ageb	0.34	0.14	1.4 (1.1-1.8)	0.013
V30	0.05	0.02	1.1 (1–1.1)	0.011

^aScaled by 10.

^bStandardized age was used with origin corresponding to the mean of 64.

Note: SE = standard error of the estimated coefficient parameter; CI = confidence interval for the hazard ratio; Stepwise backward model selection based on generalized Akaike information criterion was used; symptomatic radiation pneumonitis was conditionally independent of tumor location, stage, histology, smoking status, treatment type, and MLD in the presence of SUV₉₅, V₃₀, and age; p-values derived from two-sided hypothesis tests using Wald chi-square; the rate of symptom development was increased significantly with SUV₉₅, V₃₀, and age.