Table 1. Characteristics of the included studies.

No.	Author	Year	Country	Cancer Type	Case(cancer/ control)	Source of Control	Methylation in tumor	Methylation in Control
1	Bagci[18]	2016	Turkey(Asia)	CRC	93/14	AT	42/93	4/14
2	Laskar[19]	2015	India(Asia)	CRC	80/20	AT	27/80	6/20
3	Almeida[20]	2015	Brazil(South America)	CRC	5	AT	4/5	5/5
4	Kupčinskaitė-Noreikienė[21]	2013	Lithuanian (Europe)	GC	69	AT	33/69	32/69
5	Nomura[11]	2013	Japan(Asia)	GC	115/412	NT	95/115	201/412
6	Ye[8]	2012	China(Asia)	GC	62	AT	34/62	11/62
7	Li [22]	2011	China(Asia)	EC	47	AT	22/47	6/47
8	Hu[23]	2010	China(Asia)	GC	70/30	NT	42/70	0/30
						AT	42/70	10/70
9	Lee[12]	2009	Korea(Asia)	CRC	243/148	NT	81/243	0/148
10	Zou[24]	2009	China(Asia)	GC	16/20	NT	7/16	0/20
11	Ksiaa[25]	2009	Tunisia (Africa)	GC	68/53	AT	21/68	13/53
12	Kato[26]	2008	Japan(Asia)	GC	81/43	AT	18/81	4/43
13	Kuester[10]	2007	Germany (Europe)	EC	35/20	NT	21/35	4/20
14	Mittag [9]	2006	Germany (Europe)	CRC	22/8	AT	18/22	2/8
15	Anacleto[27]	2005	Brazil(South America)	CRC	106/30	AT	21/106	0/30
16	Chan[28]	2005	China(Asia)	GC	107/23	NT	74/107	0/23
17	Schildhaus[29]	2005	Germany (Europe)	GC	7	AT	6/7	2/7
				EC	10	AT	7/10	4/10
18	Lee [30].	2004	Korea(Asia)	CRC	149/24	NT	71/149	0/24
19	Sabbioni[31]	2003	Italy(Europe)	GC	21/6	NT	19/21	2/6
				CRC	47/4	NT	35/47	0/4
20	Waki[14]	2003	Japan(Asia)	GC	93	AT	40/93	68/93
21	Yamaguchi[32]	2003	Japan(Asia)	CRC	122/10	NT	67/122	0/10
22	To[33]	2002	China(Asia)	GC	31/10	NT	22/31	0/10

NT: normal tissue

AT: normal tissue adjacent to the tumor