Table 2.

Summary of HRs and their 95% CI.

Author	Year	HR	LCI	UCI
Kikuchi et al. [16]	2010	2.08	1.32	3.23
Takawa et al. [17]	2011	1.482	1.051	2.091
Bondgaard et al. [20]	2012	0.28	0.13	0.57
Huqun et al. [15]	2012	2.8	1.19	6.59
Chen et al. [14]	2013	1.975	0.775	5.031
Xu et al. [19]	2014	4.32	2.13	8.73
Geng et al. [21]	2015	2.39	1.66	3.46
Toyokawa et al. [22]	2017	2.28	1.02	5.09
Toyokawa et al. [23]	2018	0.57	0.16	2.01
Matsubara et al. [24]	2019	2.64	1.41	4.94
Behrens et al. [13]	2013	1.943	1.387	2.723
Li et al. [12]	2014	0.45	0.15	1.35

CI: confidence interval; HR: hazard ratio; LCI: low confidence interval; UCI: upper confidence interval.