Table 2.

Summary of the results of subgroup analysis between the two groups according to NOS scale and type of study.

Variables	Num.	NA group, events/total	Control group, events/total	RR (95% CI)	P value	Cross-study heterogeneity
						χ 2	df	I 2 (%)	P value
Studies with no less than 8 stars according to Newcastle-Ottawa scale
1-year recurrence	3	75/554	921/4124	0.54 [0.32, 0.91]	0.02	3.09	2	35	0.21
3-year recurrence	3	181/554	1829/4124	0.63 [0.38, 1.05]	0.08	7.18	2	72	0.03
1-year overall survival	3	430/485	429/561	1.13 [1.07, 1.20]	<0.0001	1.31	2	0	0.52
3-year overall survival	2	141/231	206/411	2.32 [0.39, 13.89]	0.36	3.92	1	74	0.052
5-year overall survival	3	181/270	84/159	2.99 [0.24, 34.42]	0.40	3.72	1	73	0.05
1-year disease-free survival	3	314/485	282/561	1.19 [1.09, 1.44]	0.07	3.99	2	50	0.14
5-year disease-free survival	2	126/270	57/159	2.96 [0.24, 36.31]	0.40	3.64	1	73	0.06
Studies with RCTs excluded
1-year recurrence	5	77/584	930/4167	0.51 [0.33, 0.80]	0.003	4.99	4	20	0.29
3-year recurrence	5	192/584	1854/4167	0.65 [0.44, 0.95]	0.03	10.25	4	61	0.04
1-year overall survival	7	553/638	537/718	1.13 [1.08, 1.19]	<0.00001	1.95	6	0	0.92
3-year overall survival	6	264/376	310/584	1.27 [1.10, 1.47]	0.001	9.25	5	46	0.10
5-year overall survival	7	436/580	360/668	1.39 [1.21, 1.59]	<0.00001	12.19	6	51	0.06
1-year disease-free survival	10	565/585	618/1097	1.14 [1.02, 1.28]	0.02	15.92	9	43	0.07
3-year disease-free survival	7	484/1070	110/347	1.49 [1.11, 1.99]	0.008	9.20	6	35	0.16
5-year disease-free survival	6	189/437	100/308	1.45 [1.02, 2.13]	0.04	8.83	5	43	0.12

Num.: number; RR: risk ratio; CI: confidence interval; df: degrees of freedom.