Table 2.

Methodological quality of the included studies according to the Newcastle-Ottawa scale.

Gene-polymorphism	Author	Ethnicity	Adequacy of case definition	Representativeness of the cases	Selection of controls	Definition of controls	Comparability cases/controls	Ascertainment of exposure	Same method of ascertainment	Non-response rate
XRCC1-rs25487	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Matullo et al.	Mixed	*	*	NA	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Arizono et al.	Asian	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	*	NA	*	*
	Sak et al.	Caucasian	*	*	NA	*	**	*	*	*
	Sanyal et al.	Caucasian	*	*	NA	*	**	NA	*	*
	Matullo et al.	Mixed	*	*	NA	*	**	*	*	*
	Fontana et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Broberg et al.	Asian	*	*	NA	*	**	NA	*	*
	Matullo et al.	Caucasian	*	*	NA	*	*	*	*	*
	Shen et al.	Caucasian	*	*	NA	*	**	*	*	*
	Ramaniuk et al.	Caucasian	*	*	NA	*	**	*	*	*
	Zhi et al.	Asian	*	*	*	*	**	*	*	*
	Wang et al.	Asian	*	*	NA	*	**	*	*	*
	Andrew et al.	Mixed	*	*	NA	*	**	*	*	*
	Kelsey et al.	Mixed	*	*	*	*	**	*	*	*
	Huang et al.	Caucasian	*	*	NA	*	**	*	*	*
	Gao et al.	Mixed	NA	*	NA	*	*	NA	*	-
	Hamano et al.	Asian	*	*	NA	*	**	*	*	*
	Berhane et al.	Asian	*	*	NA	*	**	NA	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Abe et al.	Caucasian	*	*	NA	*	**	*	*	*
	vanGils et al.	Caucasian	*	*	*	*	**	NA	*	*
	Xu et al.	Asian	*	*	*	*	**	*	*	*
	Ritchey et al.	Asian	*	*	*	*	**	*	*	*
	Hirata et al.	Asian	*	*	NA	*	**	NA	*	*
	Dhillon et al.	Caucasian	*	*	NA	*	**	NA	*	*
	Kuasne et al.	Caucasian	*	*	*	*	**	NA	*	*
	Zhu et al.	Asian	*	*	NA	*	**	NA	*	*
	Chen et al.	Mixed	*	*	NA	*	**	*	*	*
	Chen et al.	Mixed	*	*	NA	*	**	*	*	*
	Rybicki et al.	Mixed	*	*	NA	*	*	*	*	*
	Rybicki et al.	Mixed	*	*	NA	*	*	*	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Hirata et al.	Asian	*	*	NA	*	**	NA	*	*
XRCC1-rs1799782	Huang et al.	Caucasian	*	*	NA	*	**	*	*	*
	Andrew et al.	Mixed	*	*	NA	*	**	*	*	*
	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Matullo et al.	Caucasian	*	*	*	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	*	NA	*	*
	Fontana et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Wang et al.	Asian	*	*	NA	*	**	*	*	*
	Sak et al.	Caucasian	*	*	NA	*	**	*	*	*
	Matullo et al.	Caucasian	*	*	NA	*	*	*	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Hamano et al.	Asian	*	*	NA	*	**	*	*	*
	Hirata et al.	Asian	*	*	NA	*	**	NA	*	*
	Zhu et al.	Asian	*	*	NA	*	**	NA	*	*
	vanGils et al.	Caucasian	*	*	*	*	**	NA	*	*
	Xu et al.	Asian	*	*	*	*	**	*	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Mittal et al.	Asian	*	*	NA	*	*	NA	*	*
XRCC1-rs25489	Sak et al.	Mixed	*	*	NA	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	*	NA	*	*
	Wang et al.	Asian	*	*	NA	*	**	*	*	*
	Xu et al.	Asian	*	*	*	*	**	*	*	*
	vanGils et al.	Caucasian	*	*	*	*	**	NA	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Zhu et al.	Asian	*	*	NA	*	**	NA	*	*
XRCC1-rs915927	Sak et al.	Caucasian	*	*	NA	*	**	*	*	*
	Matullo et al.	Caucasian	*	*	*	*	**	*	*	*
	Matullo et al.	Caucasian	*	*	NA	*	*	*	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
	Agalliu et al.	Mixed	*	*	NA	*	**	NA	*	*
XRCC1-rs3213245	Wang et al.	Asian	*	*	NA	*	**	*	*	*
	Sak et al.	Caucasian	*	*	NA	*	**	*	*	*
	Zhi et al.	Asian	*	*	*	*	**	*	*	*
XRCC2-rs3218536	Nowacka-Zawisza et al.	Caucasian	NA	*	NA	*	**	*	*	*
	Matullo et al.	Caucasian	*	*	NA	*	*	*	*	*
	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
XRCC3-rs861539	Narter et al.	Caucasian	*	*	NA	*	**	*	*	*
	Fontana et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Matullo et al.	Caucasian	*	*	*	*	**	*	*	*
	Zhu et al.	Asian	*	*	NA	*	**	NA	*	*
	Andrew et al.	Mixed	*	*	NA	*	**	*	*	*
	Gangwar et al.	Asian	*	*	NA	*	*	*	*	*
	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
	Mittle et al.	Asian	*	*	NA	*	**	*	*	*
	Matullo et al.	Caucasian	*	*	NA	*	*	*	*	*
	Sanyal et al.	Caucasian	*	*	NA	*	**	NA	*	*
	Shen et al.	Caucasian	*	*	NA	*	**	*	*	*
	Narter et al.	Caucasian	*	*	NA	*	**	*	*	*
	Wu et al.	Caucasian	*	*	NA	*	**	*	*	*
	Broberg et al.	Asian	*	*	NA	*	**	NA	*	*
	Stern et al.	Mixed	*	*	NA	*	**	*	*	*
	Matullo et al.	Mixed	*	*	NA	*	**	*	*	*
	Yang et al.	Asian	*	*	NA	*	**	*	*	*
	Hao et al.	Asian	NA	*	NA	*	**	NA	*	*
XRCC3-rs861539	Nowacka-Zawisza et al.	Caucasian	NA	*	NA	*	**	*	*	*
	Ritchey et al.	Asian	*	*	*	*	**	*	*	*
	Dhillon et al.	Caucasian	*	*	NA	*	**	NA	*	*
	Mandal et al.	Asian	*	*	NA	*	**	*	*	*
	Hamano et al.	Asian	*	*	NA	*	**	*	*	*
	Dhillon et al.	Caucasian	*	*	NA	*	**	NA	*	*
XRCC3-rs1799796	Matullo et al.	Caucasian	*	*	*	*	**	*	*	*
	Mittle et al.	Asian	*	*	NA	*	**	*	*	*
	Wu et al.	Caucasian	*	*	NA	*	**	*	*	*
	Broberg et al.	Asian	*	*	NA	*	**	NA	*	*
	Matullo et al.	Mixed	*	*	NA	*	**	*	*	*
XRCC4-rs1805377	Mandal et al.	Asian	*	*	NA	*	*	*	*	*
	Luedeke et al.	Caucasian	*	*	NA	*	**	NA	*	*
	Broberg et al.	Asian	*	*	NA	*	**	NA	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Figueroa et al.	Caucasian	*	*	NA	*	*	NA	*	*
XRCC4-rs6869366	Chang et al.	Asian	*	*	NA	*	**	*	*	*
	Mandal et al.	Asian	*	*	NA	*	*	*	*	*
	Mittal et al.	Asian	*	*	NA	*	*	NA	*	*
	Chang et al.	Asian	*	*	NA	*	**	*	*	*
XRCC4-rs28360071	Mandal et al.	Asian	*	*	NA	*	**	*	*	*
	Mittal et al.	Asian	*	*	NA	*	**	*	*	*
	Chang et al.	Asian	*	*	NA	*	**	*	*	*
XRCC7-rs7003908	Hirata et al.	Asian	*	*	NA	*	**	NA	*	*
	Mandal et al.	Asian	*	*	NA	*	**	*	*	*
	Wang et al.	Asian	*	*	NA	*	**	*	*	*
	Gangwar et al.	Asian	*	*	NA	*	*	*	*	*
	Zhi et al.	Asian	*	*	*	*	**	*	*	*
	Hirata et al.	Asian	*	*	NA	*	**	NA	*	*

H′ quality choices with a ‘star’. A study can be awarded a maximum of one star for each numbered item within the Selection and Exposure categories. A maximum of two stars can be given for Comparability.