2. Analysis results of Cox regression.

Variables	Parameter estimates	Standard error	χ2	P	HR (95% CI)
HR, hazard ratio; 95% CI, 95% confidence interval.
Group	0.18315	0.73104	0.0628	0.8022	1.201 (0.287−5.033)
Operation time	−0.00704	0.03009	0.0547	0.8151	0.993 (0.936−1.053)
Gender	0.06749	0.48523	0.0193	0.8894	1.070 (0.413−2.769)