Table 2. Weighted linear regression analyses of correlations between surrogate end points and OS.

	No. of patients (paired arms)	Intercept	Slope	r2 (95% CI)	P-value
Median OS ratio vs median PFS ratio
All trials	2148 (19)	0.032	0.624	0.66 (0.32–0.85)	<0.001
Trials with gemcitabine-containing therapies	1933 (15)	0.050	0.623	0.78 (0.46–0.92)	<0.001
Trials with targeted agents	953 (7)	0.112	0.328	0.78 (0.14–0.96)	0.004
Median OS ratio vs RR ratio
All trials	2040 (17)	0.013	0.282	0.29 (0.01–0.65)	0.021
Trials with gemcitabine-containing therapies	1880 (14)	0.020	0.268	0.39 (0.02–0.75)	0.013
Trials with targeted agents	953 (7)	0.119	0.155	0.43 (0.03–0.89)	0.090
Median OS ratio vs DCR ratio
All trials	1989 (17)	−0.038	0.227	0.34 (0.02–0.69)	0.011
Trials with gemcitabine-containing therapies	1832 (14)	−0.037	0.293	0.60 (0.17–0.86)	<0.001
Trials with targeted agents	953 (7)	0.094	0.312	0.44 (0.03–0.89)	0.086
Sensitivity analyses between PFS and OS
Trials reporting median PFS	1984 (16)	0.026	0.596	0.62 (0.23–0.85)	<0.0001
Trials reporting both HRs for PFS and OSa	1287 (9)	−0.075	0.528	0.63 (0.07–0.91)	0.006
Trials with total sample size ⩾100 enroled patients	1392 (8)	0.037	0.597	0.60 (0.02–0.92)	0.015
Not early closed trials	1970 (17)	0.042	0.630	0.64 (0.27–0.86)	<0.001

Abbreviations: CI=confidence interval; DCR=disease control rate; HR=hazard ratio; OS=overall survival; PFS=progression-free survival; RR=response rate; r²=coefficient of determination.

^aThe correlation between PFS HRs and OS HRs.