Table 5 Cox Proportional-hazards Regression Model for Recurrence-free Survival and Overall Survival in Patients with IMA ≤ 2 cm (n = 302) and > 2 to 3 cm of SEER Cohort (n = 178)

IMA ≤ 2 cm

 Age (> 65 vs. ≤ 65)

0.363

0.758

 Gender (male vs. female)

0.946

0.979

 Race/ethnicity (white vs. non-white)

0.376

0.700

 Tumor location (upper and middle vs. lower)

0.170

0.388

 Surgical procedure (limited resection vs. lobectomy)

0.704

0.830

 Lymph node status (positive vs. negative)

< 0.001

8.234 (3.586–18.904)

< 0.001

< 0.001

7.778 (3.730-16.217)

< 0.001

IMA > 2 to 3 cm

 Age (> 65 vs. ≤ 65)

0.518

0.240

 Gender (male vs. female)

0.391

0.468

 Race/ethnicity (white vs. non-white)

0.634

0.478

 Tumor location (upper and middle vs. lower)

0.552

0.206

 Surgical procedure (limited resection vs. lobectomy)

< 0.001

10.066 (3.571–28.376)

< 0.001

< 0.001

8.527 (3.355–21.676)

< 0.001

 Lymph node status (positive vs. negative)

< 0.001

14.346 (4.962–41.476)

< 0.001

< 0.001

11.199 (4.188–29.950)

< 0.001