TABLE 4.

Evaluation of Potential Predictors of Adherence to and Duration of Treatment with Oral Erlotinib (N = 1,088)

Parameter	Adherencea			Persistence
	OR	(95% CI)	P Value	HR	(95% CI)	P Value
Age, years	1.01	(0.99-1.03)	0.26	0.99	(0.98-1.00)	0.22
Gender (male vs. female)	1.02	(0.80-1.30)	0.88	1.07	(0.93-1.24)	0.33
Race/ethnicity (black/other vs. white)	1.26	(0.91-1.75)	0.16	0.87	(0.72-1.05)	0.1535
Patient’s geographic region (Northeast vs. South)	2.07	(1.00-4.27)	0.07	0.59	(0.35-1.00)	0.05
Patient’s geographic region (West vs. South)	1.18	(0.76-1.83)	0.76	0.83	(0.63-1.09)	0.18
Patient’s geographic region (Midwest vs. South)	1.00	(0.75-1.32)	0.11	1.04	(0.88-1.22)	0.65
Population density (urban vs. rural)	1.07	(0.70-1.62)	0.49	0.81	(0.64-1.02)	0.08
Population density (suburban vs. rural)	1.38	(0.87-2.19)	0.07	0.73	(0.56-0.95)	0.02
Low-income subsidy recipient (Medicare Advantage only)	0.56	(0.36-0.89)	0.01	2.33	(1.67-3.26)	< 0.0001
Dual eligible recipient (Medicare Advantage only)	1.20	(0.78-1.85)	0.42	2.09	(1.48-2.96)	< 0.0001
Commercial vs. Medicare	1.06	(0.62-1.80)	0.84	0.48	(0.35-0.66)	< 0.0001
Deyo-Charlson Comorbidity Index	1.01	(0.96-1.07)	0.64	1.01	(0.98-1.04)	0.51
Diagnosis of metastatic disease	1.27	(0.88-1.84)	0.20	1.07	(0.88-1.31)	0.48
Diagnosis of other neoplasms	1.20	(0.92-1.57)	0.17	1.00	(0.86-1.16)	0.97
Previous IV therapy	0.73	(0.56-0.96)	0.03	1.06	(0.91-1.24)	0.46
Baseline total health care costs (per $1,000)	1.03	(1.00-1.06)	0.02	1.01	(1.00-1.03)	0.13
Erlotinib out-of-pocket costs per prescription (per $100)	0.97	(0.95-0.98)	0.0001	1.15	(1.13-1.17)	< 0.0001

Note: Intercept Only: -2 log likelihood 1671.394; Full Model: -2 log likelihood 1616.413 c2 = 54.9812 df = 17, 0.0001; c = 0.628.

^aAdherence defined as medication possession ratio > 80%.

CI = confidence interval; df = degrees of freedom; HR = hazards ratio; IV = intravenous; OR = odds ratio.