Table 4.

Cox Proportional Hazards Model (using backwards stepwise regression, with final model step shown). Variables entered into the model included age, gender, race, distance from treatment center, insurance status, population type, income, facility type, Charlson/Deyo comorbidity score, clinical T and N stage, histologic type, neoadjuvant therapy type, pathologic tumor size (mm), margin status, number of positive lymph nodes, readmission history, and adjuvant therapy status.

Variable	Hazard Ratio (95% CI)	P value
Age (by year)	1.01 (1.01 – 1.02)	<0.001
Female Gender	0.83 (0.72 – 0.91)	0.01
Income ≥ $35,000	0.79 (0.69 – 0.91)	0.01
Private Insurance	0.86 (0.77 – 0.97)	0.01
Academic cancer center	0.87 (0.80 – 0.98)	0.02
Charlson/Deyo Score (ref: 0)
1	1.17 (1.03 – 1.32)	0.02
≥2	1.09 (0.86 – 1.38)	0.48
Clinical T stage (ref: T0-T1)
T2	0.93 (0.73 – 1.19)	0.57
T3	0.99 (0.80 – 1.24)	0.97
T4	1.55 (1.12 – 2.16)	0.01
TX	1.16 (0.88 – 1.54)	0.30
Clinical N stage (ref: N0)
N1	1.18 (1.05 – 1.32)	0.01
≥ N2	1.38 (1.06 – 1.80)	0.02
NX	1.39 (1.10 – 1.74)	0.01
Positive margin status (R1)	1.85 (1.56 – 2.21)	<0.001
Positive lymph nodes (per node)	1.08 (1.06 – 1.09)	<0.001
30-day readmission	1.47 (1.21 – 1.78)	<0.001
Adjuvant chemotherapy	0.74 (0.62 – 0.89)	0.001