Table 1.

The features of included studies

Author	Year	Country	Size of study	Tumor locations	Tumor stage	Treatment	Data of OS or DFS
da Silva et al6	2015	Brazil	102	OSCC	I–IV	Surgery	OS (DSS)
Ahmed et al7	2014	Egypt	75	LSCC	I–IV	Surgery, radiotherapy, and chemotherapy	OS and DFS
Pectasides et al8	2014	USA	67	HNSCC	I–IV	Surgery and radiotherapy	DFS (PFS)
Psyrri et al9	2014	Greece	289	LSCC	I–IVa	Surgery and radiotherapy	OS and DFS
Fan et al10	2013	Taiwan	112	OSCC	In situ–IV	Surgery	OS
Kaur et al11	2013	India	72	OSCC	I–IVa	Surgery and radiotherapy	DFS
Imajyo et al12	2012	Japan	152	OSCC	NA	Surgery	OS and DFS
Li et al13	2012	People’s Republic of China	64	LSCC	I–IV	Surgery and radiotherapy	OS and DFS
Ukpo et al14	2012	USA	154	Oropharyngeal SCC	I–IV	Surgery, radiotherapy, and chemotherapy	OS
Zhao et al15	2012	People’s Republic of China	98	OSCC	I–IV	Surgery and radiotherapy	OS and DFS
Liu et al16	2010	People’s Republic of China	83	OSCC	I–IV	Surgery	OS
Zou et al17	2010	People’s Republic of China	150	LSCC	I–IV	Surgery	DFS
Diniz-Freitas et al18	2006	Spain	47	OSCC	I–IV	Surgery and radiotherapy	OS and DFS
Hung et al19	2006	People’s Republic of China	45	OSCC	III–IV	Surgery	OS
Kurtz et al20	2006	USA	45	HNSCC	I–IV	Surgery	OS and DFS
Ueda et al21	2006	Japan	131	OSCC	I–IV	Surgery and chemotherapy	DFS
Bosch et al22	2005	Germany	151	HNSCC	I–IV	Surgery	OS
Lim et al23	2005	South Korea	84	OSCC	I–IV	Surgery	OS
Nakanishi et al24	2004	Japan	91	OTSCC	II–IV	Surgery	OS

Abbreviations: OS, overall survival; DFS, disease-free survival; OSCC, oral squamous cell carcinoma; DSS, disease-specific survival; LSCC, laryngeal squamous cell carcinoma; HNSCC, head and neck squamous cell carcinoma; PFS, progression-free survival; SCC, squamous cell carcinoma; OTSCC, oral tongue squamous cell carcinoma; NA, not available.