Table 1. Characteristics of eligible studies.

Publication	Year	Country	Cancer subtype	No. of patients	Median age (years)	Median follow-up (years)	Outcome	Survival analysis	NOS (score)
Markiewicz	2012	Poland	II-III BC	36	56.5	4.2	DFS, OS	multivariate	8
Montserrat	2011	Spain	invasive BC	76	67	4.5	DFS, OS	multivariate	8
Riaz	2012	Netherlands	primary BC	1427	55	8.7	DFS, OS	multivariate	8
Soini	2011	Finland	invasive BC	387	NR	NR	OS	univariate	7
Xu	2014	China	primary BC	137	NR	5	DFS, OS	multivariate	8
Zhang	2015	China	invasive BC	408	50	1.3	DFS, OS	univariate	7
Zhao	2013	China	primary BC	200	50	NR	OS	univariate	7

BC, breast cancer; NR, not reported; DFS, disease-free survival; OS, overall survival; NOS, Newcastle Ottawa Scale