Table 1a. Features of included studies.

References	Year	Patients (n)	Mean age	Methods •	ERb assessment ••	ERb status		Median Follow up(Months)	Quality Score
						ERb+	ERb−
Borgquist et al.[11]	2008	512	64.2	i	ii	167	312	106	*****
		114 #				60	54	NA
		139 ##				71	68	NA
Chantzi et al.[20]	2013	95	52	i	i	b1:66 b2:65	b1:29 b2:30	NA	******
Gruvberger-Saal et al.[5]$, ¶¶¶¶	2007	425	NA	i	ii	262	91	174	*******
Guo et al. [21]¶¶¶¶¶	2014	490	49	i	ii	110	380	60	*******
Honma et al. [2]§	2008	442	56	i	ii	405	37	133	******
Hopp et al.[12]	2004	305	62	iii	v	141	164	65	*****
		186#				89	97	74
		119 ##				52	67	50
Kim et al.[13]	2012	139	NA	ii	iii	53	87	48	*****
Mahle et al.[14]§	2009	145	63	i	ii	129	16	165	*******
Mann et al.[1]	2001	47 ##	NA	i	ii	33	14	88	****
		118#	NA		ii	78	40	49
Markey et al.[28]	2009	121	54	ii	iii	50	71	38	***
Myers et al.[15]	2004	150	NA	i	i	87	63	27	***
Nakopoulou et al.[3]	2004	181	61	i	ii	128	50	76	*****
Novelli et al.[6]	2008	936	NA	i	ii	520	416	50	*******
Omoto et al.[18]	2002	57	60.9	i	ii	15	42	48	***
Omoto et al.[17]	2001	88	54 &	i	i	52	36	NA	****
O'Neill et al. ¶[16]	2004	167	NA	i	ii	117	10	NA	******
			NA	ii	iii	86	35
Palmieri et al.[19]	2004	82	59	i	i	33	46	96 ¶¶	****
Qui et al.[22]	2009	308	58	i	ii	123	185	48	***
Shaaban et al.[23]	2008	880	NA	i	i, ii	558	112	94	******
Sugiura et al.[24]	2007	150	53	i	i	103	47	58	***
				ii	iii	52	98
Vinayagam et al. [4]¶,§	2007	141	68	i	i	100	41	BCS:71; BCR:79	*****
		100		ii	iii	34	30
Wen et al.[25]	2002	116	53.7	iii	v	40	76	35.3	******
Wimberly et al.[26]	2014	Yale-1:649	NA	iv	iv	b1:228 b5:209	b1:228 b5:209	95	*****
		Yale-2:398				b1:147 b5:153	b1:148 b5:152	123	****
		Toronto: 976				b1:225 b5:153	b1:225 b5:153	98.2	****
		NCI-PBCS: 1375				b5:467	b5:468	116	****
Yan et al.¶¶¶,§[27]	2011	147	NA	i	ii	90	20	64	***
Zhang et al.[29]	2014	279	48.8	i	ii	40	109	92	***

^•i.IHC; ii, PCR; iii, Immunoblot; iv. TMA

^••i, Allred score; ii, Proportion of positive cells; iii, Ct value; iv, AQUA score; v, Band intensities

^#Tamoxifen/endocrine-treated subgroup

^##untreated subgroup; & Median

^¶Postmenopausal patients.

^¶¶Estimated based on the description in the text.

^¶¶¶Familial breast cancer patients.

^¶¶¶¶Stage II patients.

^¶¶¶¶¶This group was reported in three publications involving the same study population. We selected the study with the longest follow-up period for analysis.

NA, Not available; ER, estrogen receptor;