Table 1.

Quality assessment for the 17 included articles based on Newcastle–Ottawa quality assessment scale.

	Selection			Comparability			Exposure
Refs.	Inclusion criteria	Sample size >50	Endpoint	Anatomical location	Enneking stage	Chemotherapy	Local recurrence	5-year overall survival	Metastatic	NOS
Abudu et al. [12]	*	–	*	*	*	*	*	*	*	8*
Bacci et al. [13]	*	–	*	*	*	*	*	–	–	6*
Bacci et al.b[14]	*	*	*	–	–	*	*	*	*	7*
Bramer et al. [15]	*	*	*	*	–	*	*	–	–	6*
Ferguson et al. [16]	*	–	*	*	–	*	*	–	–	5*
Guo et al. [17]	*	–	*	*	–	*	*	–	*	6*
Hegyi et al. [18]	*	*	*	–	–	*	*	*	*	7*
Jiang et al. [19]	*	*	*	*	*	*	*	–	–	8*
Kim et al. [20]	*	–	*	*	–	*	*	–	–	5*
Ma et al. [21]	*	*	*	*	–	*	–	*	–	6*
Mavrogenis et al. [22]	*	–	*	*	–	*	*	–	*	6*
Niu et al. [23]	*	–	*	*	*	*	*	*	*	8*
Robert et al. [24]	*	*	*	*	–	–	*	*	–	6*
Scully et al. [25]	*	*	*	*	*	*	*	*	–	8*
Xu et al. [26]	*	*	*	*	*	*	*	*	–	8*
Zhang et al. [27]	*	–	*	*	*	*	*	–	*	7*
Zhao et al. [28]	*	*	*	*	*	*	*	–	–	7*