High expression of anti-apoptotic protein Bcl-2 is a good prognostic factor in colorectal cancer: Result of a meta-analysis

Table 1 Main characteristics of the studies included in the meta-analysis

Ref.	Year	Country	Tumor location	Patient(P/N)	Age	Stage	Treatment before surgery	Follow-up time Median(range)	Detection method	Antibody source	Antibody dilution	Cut off value	HR(95%CI) estimation	Quality Score
Cai et al[21]	2016	China	Colon and rectum	117(34/83)	52.0 yr	I-IV	No	NA	IHC	Thermo Scientific	1:50	> 10%	OS = 0.7 (0.34-1.45) Multivariate	7
					(24-87 yr)
Melincovici et al[6]	2016	Romania	Colon	31(12/19)	63 ± 11.71 yr	A-D	Yes	NA	TMA/IHC	Dako	1:100	> 5%	OS = 0.211 (0.026-1.718) Univariate	8
						(Ducks)
Huang et al[22]	2015	China	Colon and rectum	190(85/105)	NA	A-D	No	986 d	IHC	Genetex	NA	Multiply the intensity score by the percentage of labeled cells > 150	OS = 2 (1.21-3.3) Multivariate	8
						(Ducks)		(21-2572d)					RFS = 1.32 (0.82-2.13) Multivariate
Balzi et al[15]	2015	Italy	Colon and rectum	321 (153/168)	< 85 yr	I-III	No	NA	IHC	Dako	1:50	> 5%	OS = 0.87 (0.51-1.48) Univariate	8
													DFS = 0.971 (0.654-1.449) Multivariate
Belt et al[23]	2014	Netherlands	Colon	160 (81/76)	72.4 yr	T1-4,	Yes	46.9 mo	TMA/IHC	Dako	1:300	Score ≥ 1	DFS = 0.409 (0.256-0.653) Univariate	6
					(34.5-94.0 yr)	N1-2, M0		(3.0-148.6 mo)
Fucini et al[9]	2012	Italy	Rectum	66 (27/39)	67 ± 9 yr	II-III	Yes	105.5 ± 39.6 mo	IHC	Dako	1:50	> 10%	OS = 2.526 (1.146-5.565) Univariate	5
Xu et al[10]	2009	China	Colon and rectum	119 (33/86)	57 yr	I-IV	No	95 mo	IHC	Dako	1:50	> 10%	OS = 3.064 (1.217-7.718) Multivariate	5
					(31-74 yr)			(1-203 mo)
Zlobec et al[24]	2008	Switzerland	Colon and rectum	1420 (NA)	NA	pT1-4,	NA	NA	TMA/IHC	NA	NA	> 30%	OS = 1.15 (0.94-1.39) Multivariate	5
						N0-N2
Torsello et al[7]	2008	Italy	Colon and rectum	1340 (650/690)	NA	A-D	Yes	5 yr	IHC	Dako	NA	> 30%	OS = 0.221 (0.105-0.464) Univariate	6
						(Ducks)
Cahlin et al[25]	2008	Sweden	Colon	22 (NA)	75 ± 9 yr	A-D	No	68 mo	IHC	Santa Cruz Biotechnology	0.25 μg/mL	NA	OS = 1.43 (1-2.06) Multivariate	5
						(Ducks)		(3.6-127.4 mo)
Tsamandas et al[8]	2007	Greece	Rectum	28 (17/11)	64 yr	B2 and C	No	47.19 ± 6.2 mo	IHC	Dako	1:40	> 5%	OS = 0.032 (0.007-0.158) Univariate	5
					(27-76 yr)	(Ducks)
Meleth et al[26]	2007	United Kingdom	Colon and rectum	491 (NA)	NA	I-IV	No	5 yr	IHC	NA	NA	Score ≥ 0.5	OS = 0.67 (0.493-0.92) Multivariate	6
Zavrides et al[12]	2006	Greece	Colon and rectum	100 (27/73)	NA	I and III	No	7 yr	IHC	Biogenex	1:10	> 5%	OS:0.273(0.139-0.534) Univariate	7
								(5-9 yr)
Georgiou et al[27]	2006	Greece	Colon and rectum	170 (64/106)	NA	B and C	NA	46 mo	IHC	Dako	1:80	> 10%	OS = 0.556 (0.326-1.031) Univariate	7
						(Ducks)		(3-93 mo)
Chatla et al[28]	2005	United States	Colon and rectum	158 (89/69)	NA	II and III	No	7.31 yr	IHC	Cambridge Laboratories	1:80	Score ≥ 0.5	RFS = 0.45 (0.083-2.441) Multivariate	6
								(< 1-> 20 yr)
Zhao et al[29]	2005	China	Colon and rectum	93 (53/40)	51 yr	A-C	NA	60 mo	IHC	NA	NA	Score ≥ 2	OS = 0.505 (0.317-0.804) Univariate	6
					(median)	(Ducks)		(median)
Lustosa et al[16]	2005	Brazil	Colon and rectum	116 (58/58)	63.4 yr	I-IV	No	28.5 mo	IHC	Dako	NA	> 10%	OS = 0.858 (0.433-1.698) Univariate	6
					(30-87 yr)			(2-96 mo)
Krajewska et al[13]	2005	Sputh Korea	Colon and rectum	106 (NA)	NA	II	No	66 mo	TMA/IHC	NA	1:2000	NA	OS = 0.251 (0.111-0.567) Multivariate	6
								(median)
Rosati et al[30]	2004	Italy	Colon and rectum	103 (41/62)	66 yr	B and C	Yes	5 yr	IHC	Dako	NA	> 10%	OS = 0.71 (0.37-1.35) Univariate	7
					(29-79 yr)	(Ducks)							DFS = 1 (0.51-1.96) Univariate
Garrity et al[31]	2004	Canada	Colon and rectum	366 (97/269)	NA	B2 and C	Yes	8.7 yr	IHC	Dako	1:50	> 10%	OS = 0.99 (0.69-1.429) Multivariate	5
						(Ducks)		(median)					DFS = 0.971 (0.654-1.449) Multivariate
Kouraklis et al[32]	2003	Greece	Colon	113 (55/58)	70.9 yr	B and C	No	NA	IHC	Dako	1:50	> 5%	OS = 0.523 (0.304-0.903) Univariate	8
					(42-94 yr)	(Ducks)
Scopa et al[33]	2003	Greece	Colon and rectum	117 (76/41)	66 yr	A-D	No	97 mo	IHC	Dako	1:40	Cytoplasmic staining	OS = 1.55 (0.7-3.4) Multivariate	8
					(25-82 yr)	(Ducks)		(44-142 mo)
Sun et al[34]	2003	Sweden	Colon and rectum	138 (82/56)	71 yr	A-D	NA	NA	IHC	Nova Castra Laboratories Ltd	1:80	> 5%	OS = 0.504 (0.221-1.146) Univariate	7
					(43-94 yr)	(Ducks)
Bendardaf et al[35]	2003	Finland	Colon and rectum	58 (45/13)	60.3 yr	T2-X,N0-X,M0-1	Yes	NA	IHC	Dako	1:50	Sum the intensity score and expression score ≥ 1.10	OS = 1.02(0.7-11.5) Univariate	6
					(24.3-78.2 yr)
Elkablawy et al[36]	2001	United Kingdom	Colon and rectum	52 (18/34)	68.8 yr	pT2-4,	NA	43.5 mo	IHC	Dako	4 μg/mL	Multiply the intensity score and expression score ≥ 6	OS = 0.552 (0.231-1.319) Univariate	6
					(33-93 yr)	N0-1,M0-1		(2-111 mo)
Meterissian et al[37]	2001	Canada	Colon	76 (62/14)	71.2 yr	B	No	59 mo	IHC	Dako	1:50	≥ 30% or stain intensity scale ≥ 1	OS = 0.35 (0.13-0.94) Univariate	7
					(40-89 yr)	(Ducks)		(5-110 mo)					DFS = 0.49 (0.19-1.26) Univariate
Paradiso et al[38]	2001	Italy	Colon and rectum	80 (29/51)	NA	Advanced	No	NA	IHC	Dako	1:40	> 5%	OS = 1.287 (0.76-2.183) Univariate	6
Schwandner et al[39]	2000	Germeny	Rectum	160 (47/113)	66.7 yr	I-III	No	38 mo	IHC	Dako	1:20	> 10%	DFS = 0.181 (0.056-0.585) Univariate	7
					(31-92 yr)			(12-72 mo)
Buglioni et al[40]	1999	Italy	Colon and rectum	171 (57/114)	64 yr	A-D	No	50 mo	IHC	Dako	NA	A strong homogeneous cytoplasmic immunoreaction	OS = 0.192 (0.0439-0.84) Multivariate	7
					(56-70 yr)	(Ducks)		(median)					DFS = 0.178 (0.0508-0.625) Multivariate
Leahy et al[41]	1999	Ireland	Colon and rectum	102 (22/80)	69 yr	A-C	No	9.9 yr	IHC	Dako	1:50	> 5%	OS = 0.5 (0.2-1) Multivariate	7
					(39.2-85.5 yr)	(Ducks)		(9.0-11.2 yr)
Ishijima et al[42]	1999	Japan	Colon and rectum	33 (10/23)	61.6 yr	A-D	NA	NA	IHC	Santa Cruz Biotechnology	1:50	> 30%	DFS = 1.051 (0.202-5.464) Univariate	6
					(42-86 yr)	(Ducks)
Sinicrope et al[43]	1999	United States	Colon	137 (71/66)	65.2 yr	T2-3,	No	105.5 mo	IHC	Dako	1:20	> 20%	OS = 0.46 (0.21-1.05) Multivariate	7
					(26-89 yr)	N0,M0		(2-281 mo)					RFS = 0.45 (0.21-0.96) Multivariate
Hirvikoski et al[44]	1999	Finland	Rectum	92 (62/30)	72 yr	A-D	Yes	32 mo	IHC	Dako	1:200	> 20%	OS = 0.99 (0.55-1.79) Univariate	6
					(52-90 yr)	(Ducks)		(0-306 mo)
Biden et al[45]	1999	Australia	Colon and rectum	66 (49/17)	NA	A-D	NA	NA	IHC	Dako	1:40	> 5%	OS = 0.132 (0.057-0.306) Univariate	5
						(Ducks)
Ilyas et al[46]	1998	United Kingdom	Colon and rectum	66 (40/26)	NA	B	NA	NA	IHC	Dako	1:40	Stain	RFS = 0.77 (0.62-0.96) Univariate	5
						(Ducks)
Kaklamanis et al[47]	1998	United Kingdom	Colon and rectum	224 (73/151)	NA	A-C	NA	36 mo	IHC	Dako	NA	> 10%	OS = 0.605 (0.375-0.977) Univariate	7
						(Ducks)		(1-72.5 mo)
Tollenaar et al[48]	1998	Netherlands	Colon and rectum	209 (99/110)	NA	A-C	No	NA	IHC	Boehringer Mannheim	1:200	Score ≥ 2	OS = 0.978 (0.658-1.453) Univariate	8
						(Ducks)
Bhatavdekar et al[14]	1997	India	Colon and rectum	48 (29/19)	48 yr	B and C	NA	29.95 mo	IHC	Dako	NA	> 5%	OS = 7.813 (2.375-25.64) Univariate	7
					(25-74 yr)	(Ducks)		(2-36 mo)
Baretton et al[49]	1996	Germeny	Colon and rectum	95 (64/31)	63.8 ± 12.5 yr	pT2-3,	NA	Up to 8 yr	IHC	Dianova	1:60	An unequivocally strong cytoplasmic immunoreaction	DFS = 0.504 (0.27-0.943) Univariate	6
						N0,M0
Ofner et al[50]	1995	Austria	Colon and rectum	104 (47/57)	67.8 yr	pT1-4,	NA	NA	IHC	Dako	1:300	Stain	OS = 0.443 (0.252-0.78) Univariate	7
					(35-90 yr)	N0-X,M0-1

P/N: Positive/Negative; NA: Not assessable.

Table 2 Subgroup analysis of pooled hazard ratios for colorectal cancer patients with overexpressed Bcl-2

Stratified analysis	No. of studies	No. of patients	Pooled HR (95%CI)	P value	Heterogeneity
					I² (%)	P value
No. of patients
≥ 100	22	6274	0.684 (0.54-0.866)	0.002	75.9	0.000
< 100	12	712	0.693 (0.389-1.235)	0.214	85.8	0.000
Study location
Asia	7	777	1.021 (0.488-2.136)	0.955	88.2	0.000
Europe and America	26	6143	0.691 (0.553-0.864)	0.001	73.9	0.000
Treatment before surgery
Yes	7	2056	0.772 (0.55-0.947)	0.394	73.8	0.001
No	18	2615	0.696 (0.502-0.964)	0.029	79.9	0.000
Quality score
≥ 7	18	2471	0.678 (0.499-0.92)	0.013	71.8	0.000
< 7	16	4515	0.708 (0.503-0.996)	0.047	84.9	0.000

Table 3 Bcl-2 expression and clinicopathological features of colorectal cancer

Clinicopathologial features	No. of studies	No. of patients	Pooled OR (95%CI)	P value	Heterogeneity
					I²	P value
Gender (male vs female)	11	1671	1.125 (0.865-1.463)	0.381	30.2%	0.158
Tumor location (colon vs rectum)	8	1361	1.168 (0.922-1.480)	0.199	0%	0.628
tumor grade (1 + 2 vs 3)	12	1454	2.475 (1.307-4.685)	0.005	68.4%	0.000
Ducks' stage (A + B vs C + D)	12	1572	1.630 (1.009-2.632)	0.046	78.1%	0.000