Table 1. Basic characteristics of included studies.

Study	Country	Design	Period	Primary endpoints	Sex(M/F)	LNM(+/-)	Vascular invasion(+/-)	Resection margin(+/-)	Follow-up (months)
Roayaie 1998[24]	US	Single center	1991–1997	OS/RFS	NR	8/8	NR	NR	35.7(0.1–73.2)
Jan 2005[25]	China	Single center	1997–2001	OS	128/184	NR	NR	222/90	14.1(1.05–167.6)
Jiang 2010[26]	China	Single center	1998–2008	OS	52/38	90/0	NR	NR	13.2(0.3–123)
Shen 2011[27]	China	Single center	2002–2003	OS/RFS	88/37	10/115	38/87	NR	18(3–96)
Wu 2012[28]	China	Single center	2005–2006	OS	88/26	11/103	14/100	NR	NR
Ribero 2012[30]	Italy	Multi-center	1990–2008	OS	243/191	113/321	211/223	NR	36.5
Bhudhisawasdi 2012[29]	Thailand	Single center	1998–2002	OS	116/55	NR	145/26	141/30	NR
Li 2013[32]	China	Single center	2000–2011	OS/RFS	NR	34/177	51/160	NR	NR
Liu 2013[31]	China	Single center	2005–2011	OS	48/33	50/31	NR	NR	NR
Sur 2014[33]	US	Multi-center	1998–2006	OS	NR	128/510	NR	180/458	NR
Miura 2015[34]	US	Multi-center	1998–2011	OS	NR	NR	NR	NR	NR
Li 2015[14]	China	Single center	2008–2011	OS/RFS	368/185	104/449	73/480	NR	25.3(2.2–76.2)
Okumaura 2016[36]	Japan	Single center	2004–2015	OS/RFS	67/42	32/77	69/40	18/91	NR
Luvira 2016[35]	Thailand	Single center	2004–2009	RFS	26/24	18/32	NR	27/23	NR
Hammad 2016[12]	US	Multi-center	1998–2013	OS	819/755	607/967	NR	NR	NR
Jeong 2017[13]	China	Single center	2011–2015	OS	28/14	15/27	16/26	NR	36(11–65)
Tran 2017[39]	US	Multi-center	2004–2012	OS	NR	NR	NR	NR	NR
Schweitzer 2017[37]	Germany	Single center	2000–2015	OS	111/86	45/152	44/153	NR	NR
Reames 2017[9]	International	Multi-center	1990–2015	OS	638/516	200/954	217/805	146/992	NR
Zheng 2018[11]	China	Single center	2007–2016	OS	NR	31/18	10/39	NR	NR
Lee 2019[16]	US	Multi-center	2004–2014	OS	1315/1498	582/2231	NR	649/2164	25.2(13.2–42)
Sahara 2019[38]	International	Multi-center	1990–2015	OS	NR	NR	NR	NR	21.2(11.2–38.9)

M: male; F: female; LNM: lymph node metastasis; NR: not report; OS, overall survival; RFS, recurrence-free survival.