Table 2. Meta-analysis results of the associations between metformin use and survival of lung cancer patients with diabetes.

Survival	Subgroup		Number of		Pooled analyses	P value	heterogeneity		Effect
			studies		HR(95%CI)		Ph	I2	model
DFS	Overall			6	0.65 [0.52, 0.83]	0.0004	0.1	45%	R
	Ethnicity	Asian	4		0.69 [0.59, 0.80]	<0.001	0.13	47%	F
		Western	2		0.88 [0.41, 1.90]	0.74	0.08	68%	R
	Treatment strategy	Chemoradiotherapy	2		0.88 [0.41, 1.90]	0.74	0.08	68%	R
		Chemotherapy	3		0.71 [0.61, 0.83]	<0.001	0.23	32%	F
	Subtype	NSCLC	4		0.70 [0.51, 0.96]	0.03	0.08	56%	R
		SCLC	2		0.54 [0.38, 0.77]	0.0007	0.75	0%	F
OS	Overall		11		0.78 [0.64, 0.93]	0.007	<0.001	75%	R
	Ethnicity	Asian	4		0.55 [0.46, 0.67]	<0.001	0.55	0%	F
		Western	7		0.93 [0.76, 1.13]	0.45	0.002	71%	R
	Treatment strategy	Chemoradiotherapy	2		1.00 [0.69, 1.44]	0.98	0.13	57%	F
		Chemotherapy	3		0.58 [0.47, 0.71]	<0.001	54	0%	F
		Other	6		0.84 [0.66, 1.06]	0.13	<0.001	79%	R
	Subtype	NSCLC	5		0.75 [0.58, 0.97]	0.03	0.04	60%	R
		SCLC	2		0.52 [0.39, 0.69]	<0.001	0.67	0%	F
		Other	4		0.94 [0.68, 1.29]	0.69	0.002	80%	R

NSCLC, non-small cell lung cancer; SCLC, small cell lung cancer; DFS, disease-free survival; OS, overall survival; HR, hazard ratio;

95%CI, 95% confidence interval; Ph, p value of the Q test for heterogeneity. R, random effect model; F, fixed effect model.