Table 2.

Exploratory Cox Regression Analysis of Survival Predictors after Salvage SABR

Variable*	Progression-free survival		Overall Survival
	HR (95% CI)	P	HR (95% CI)	P
Univariate analysis
Tumor size	1.90 (1.12-3.21)	0.017	1.71 (0.96-3.05)	0.067
ECOG status (0-1 vs 2-3)	0.31 (0.14-0.66)	0.003	0.20 (0.09-0.46)	<0.001
Histology (squamous vs adenocarcinoma)	2.23 (1.09-4.59)	0.029	2.59 (1.20-5.62)	0.016
Post-SABR NLR	1.25 (1.04-1.50)	0.019	1.32 (1.11-1.57)	0.002
Pre-SABR ALC	0.69 (0.42-1.13)	0.139	0.62 (0.35-1.10)	0.099
Post-SABR ALC	0.71 (0.40-1.25)	0.234	0.49 (0.24-1.01)	0.053
Pre-SABR FEV1	1.00 (0.98-1.02)	0.764	0.99 (0.97-1.00)	0.117
Post-SABR FEV1	0.99 (0.98-1.01)	0.537	0.98 (0.96-1.00)	0.021
Pre-SABR DLCO	0.98 (0.96-1.00)	0.038	0.97 (0.95-0.99)	0.004
Post-SABR DLCO	0.98 (0.96-1.00)	0.034	0.97 (0.94-0.99)	0.008
Multivariate analysis
ECOG status (0-1 vs 2-3)	0.56 (0.21-1.51)	0.253	0.45 (0.16-1.24)	0.122
Post-SABR NLR	1.25 (0.99-1.58)	0.065	1.33 (1.06-1.65)	0.012
Pre-SABR DLCO	0.99 (0.97-1.01)	0.284	0.98 (0.96-1.00)	0.092
Tumor size	1.77 (1.00-3.13)	0.052	N/A

To avoid possible collinearity between pre- and post-SABR DLCO in the multivariate model, we chose a variable that had smaller P value and most available cases in univariate analysis. Age and other clinical factors with P values >0.2 in univariate analysis are not shown.

^*ECOG status and histologic findings were treated as categorical variables; all other variables were treated as continuous variables. Abbreviations: ALC, absolute lymphocyte count; CI, confidence interval; DLCO, carbon monoxide diffusing capacity; ECOG, Eastern Cooperative Oncology Group; FEV1, forced expiratory volume in the first second of expiration; HR, hazard ratio; NLR, neutrophil-to-lymphocyte ratio; SABR, stereotactic ablative radiotherapy.