Peroxisome proliferator-activated receptor-γ 34C>G polymorphism and colorectal cancer risk: A meta-analysis

Table 1 Study characteristics

No.	Ref.	Yr	Country	Number of cases					Number of controls					34G allele fre-quency in control	P1
				CC	CG	GG	Total	CG + GG	CC	CG	GG	Total	CG + GG
1	Landi et al[5]	2003	Spain (W, E)	311	46	3	360	49	243	61	5	309	66	0.11	0.773
2	Gong et al[2]	2005	USA (W)	129	30	4	163	34	153	52	7	212	59	0.16	0.743
3	Murtaugh et al[6]	2005	USA (W)	1840	-	-	2371	531	2283	-	-	2972	689	-	-
4	Jiang et al[4]	2005	India (A)	240	57	4	301	61	230	57	4	291	61	0.11	1.000
5	Siezen et al[1]	2006	Netherlands (W, E)	160	40	1	201	41	325	71	2	398	73	0.09	0.783
6	Koh et al[7]	2006	Singapore (A)	345	-	-	362	17	1075	-	-	1164	89	-	-
7	Gunter et al[8]	2006	USA (W)	153	41	4	198	45	146	37	1	184	38	0.11	0.838
8	Theodoropoulos et al[9]	2006	Greek (W, E)	164	48	10	222	58	118	70	12	200	82	0.24	0.950
9	Vogel et al[10]	2007	Denmark (W, E)	252	96	7	355	103	550	190	13	753	203	0.14	0.816

¹P value for Hardy-Weinberg equilibrium (HWE) for peroxisome proliferator-activated receptor-γ (PPAR-γ) 34C>G polymorphism among controls. W: Western country; E: European country; A: Asian country; -: No data was shown in reference.

Table 2 Overall and group-specific summary statistics for PPAR-γ 34 C>G and colorectal, colon and rectal cancers

	No. of studies	Polymorphisms	P1	Fixed-effect OR (95% CI), P2	Random-effect OR (95% CI), P3
Colorectal cancer
Total	7	G vs C	0.010	0.88 (0.77, 1.00), 0.060	0.86 (0.69, 1.08), 0.210
	7	GG vs CC	0.720	0.85 (0.53, 1.35), 0.480	0.83 (0.52, 1.33), 0.440
	7	CG vs CC	0.020	0.86 (0.74, 1.00), 0.050	0.83 (0.65, 1.07), 0.160
	7	GG vs CG	0.990	1.10 (0.68, 1.79), 0.690	1.09 (0.67, 1.78), 0.720
	7	CG vs CC + GG	0.020	0.86 (0.74, 1.00), 0.060	0.84 (0.66, 1.07), 0.150
	7	GG vs CC + CG	0.830	0.91 (0.57, 1.44), 0.680	0.89 (0.56, 1.43), 0.630
	9	CG + GG vs CC	0.009	0.90 (0.82, 0.99), 0.030	0.84 (0.69, 1.01), 0.070
Western	6	G vs C	0.006	0.87 (0.75, 1.00), 0.050	0.85 (0.65, 1.11), 0.230
	6	GG vs CC	0.600	0.83 (0.51, 1.36), 0.470	0.81 (0.49, 1.34), 0.420
	6	CG vs CC	0.009	0.84 (0.72, 1.00), 0.040	0.81 (0.60, 1.09), 0.170
	6	GG vs CG	0.970	1.12 (0.67, 1.87), 0.670	1.11 (0.66, 1.86), 0.700
	6	CG vs CC + GG	0.010	0.85 (0.72, 1.00), 0.050	0.82 (0.61, 1.09), 0.160
	6	GG vs CC + CG	0.730	0.90 (0.55, 1.47), 0.680	0.88 (0.54, 1.45), 0.630
	7	CG + GG vs CC	0.006	0.91 (0.82, 1.01), 0.070	0.85 (0.68, 1.06), 0.140
USA	3	CG + GG vs CC	0.320	0.95 (0.84, 1.07), 0.360	0.94 (0.80, 1.11), 0.450
Europe	4	CG + GG vs CC	0.002	0.84 (0.70, 1.00), 0.060	0.79 (0.52, 1.19), 0.260
Colon cancer	4	CG + GG vs CC	0.030	0.83 (0.72, 0.96), 0.010	0.80 (0.65, 0.99), 0.040
Rectal cancer	4	CG + GG vs CC	0.050	0.98 (0.82, 1.18), 0.860	0.84 (0.58, 1.22), 0.370

¹P value for test for heterogeneity;

²P value for fixed-effect model;

³P value for random-effect mode.