Table 4.

This table depicts the bias score calculated for each study based on the Newcastle-Ottawa scale, with 9 as the highest score.

	Adeberg et al. (26)	Blumenthal et al. (25)	Han et al. (27)	Louvel et al. (28)	Nathan et al. (29)	Noel et al. (15)	Osborn et al. (30)	Pollom et al. (31)	Sun et al. (32)	Wang et al. (33)
Selection (Max = 4)	3	4	4	4	4	4	4	4	4	4
Comparability (Max = 2)	1	0	2	1	0	0	1	2	2	0
Outcome (Max = 3)	3	3	3	3	2	3	3	3	3	3
Total (Max = 9)	7	7	9	8	6	7	8	9	9	7

A higher score correlates with a lower risk of bias. Factors included for comparability include Karnofsky Performance Status and extent of resection.