Table 2. Cox regression analysis for the overall survival of NSCLC patients with SPC occurrence at different period.

SPC or not	Event (%)	HR	95% CI	P
No SPC	170,174 (75.2)	–	–	–
SPC at different time interval
0–6 months	4,439 (67.2)	0.883	0.857–0.910	0.000
0–12 months	5,209 (66.6)	0.858	0.834–0.882	0.000
0–36 months	7,229 (63.6)	0.751	0.734–0.769	0.000
0–60 months	8,389 (61.4)	0.689	0.674–0.705	0.000
0–120 months	9,122 (59.2)	0.629	0.615–0.642	0.000

NSCLC, non-small cell lung cancer; SPC, second primary cancer; HR, hazard ratio; CI, confidence interval.