Table 1.

Study characteristics

Ref.	Type of study	Year	Country	Center	Sample (patients)	Age	Gender (male/female)	Follow-up
Lee et al[36]	Retrospective	2017	Korea	Single center	202	43.4 (13.6)	43/159	NA
Liu et al[37]	Retrospective	2017	China	Single center	42	49.1 (13.5)	9/33	NA
Hakala et al[40]	Retrospective	2014	Finland	Single center	51	52	19/32	NA
Lee et al[41]	Retrospective	2012	Korea	Single center	47	> 45: 24	11/36	NA
Yasuoka et al[38]	Retrospective	2005	Japan	Single center	49	48.8 (15)	7/42	NA
Kilicarslan et al[39]	Retrospective	2003	Turkey	Single center	48	39.8	21/27	61.7 (29.7)
Akslen et al[25]	Retrospective	2000	Norway	Single center	128	45.1	36/89	145 (35.8)
Dhar et al[35]	Retrospective	1998	Japan	Single center	71	50 (9.8)	11/60	180 mo
Ishiwata et al[23]	Retrospective	1998	Japan	Single center	100	48 (9.6)	5/95	101 mo

NA: Not available.