TABLE 5.
Evaluation of Potential Predictors of Adherence to and Duration of Treatment with Oral Erlotiniba
| Parameter | Adherenceb | Persistence | ||||
|---|---|---|---|---|---|---|
| OR | (95% CI) | P Value | HR | (95% CI) | P Value | |
| Age, years | 1.02 | (0.99-1.05) | 0.2409 | 1.00 | (0.98-1.02) | 0.8951 |
| Gender (male vs. female) | 1.41 | (0.94-2.13) | 0.0996 | 0.82 | (0.65-1.03) | 0.0905 |
| Race/ethnicity (black/other vs. white) | 1.23 | (0.71-2.13) | 0.4617 | 0.89 | (0.67-1.20) | 0.4528 |
| Patient’s geographic region (Northeast vs. South) | 2.12 | (0.66-6.77) | 0.3176 | 0.69 | (0.35-1.38) | 0.2940 |
| Patient’s geographic region (West vs. South) | 1.52 | (0.79-2.92) | 0.6841 | 0.75 | (0.50-1.13) | 0.1641 |
| Patient’s geographic region (Midwest vs. South) | 1.06 | (0.66-1.68) | 0.2552 | 1.11 | (0.86-1.43) | 0.4277 |
| Population density (urban vs. rural) | 1.10 | (0.56-2.16) | 0.6366 | 0.89 | (0.62-1.27) | 0.5153 |
| Population density (suburban vs. rural) | 1.49 | (0.71-3.14) | 0.1790 | 0.83 | (0.55-1.25) | 0.3699 |
| Low-income subsidy recipient (Medicare Advantage only) | 0.72 | (0.34-1.55) | 0.4056 | 4.81 | (2.76-8.38) | < 0.0001 |
| Dual eligible recipient (Medicare Advantage only) | 0.80 | (0.38-1.70) | 0.5688 | 2.12 | (1.22-3.66) | 0.0073 |
| Line of business (commercial vs. Medicare) | 1.12 | (0.45-2.81) | 0.8010 | 0.40 | (0.24-0.66) | 0.0004 |
| Deyo-Charlson Comorbidity Index | 1.00 | (0.92-1.09) | 0.9884 | 1.01 | (0.96-1.06) | 0.7620 |
| Diagnosis of metastatic disease | 1.23 | (0.66-2.31) | 0.5187 | 1.00 | (0.73-1.37) | 0.9809 |
| Diagnosis of other neoplasms | 1.95 | (1.24-3.06) | 0.0039 | 1.01 | (0.81-1.27) | 0.9027 |
| Previous IV chemotherapy use for NSCLC | 0.72 | (0.44-1.16) | 0.1778 | 1.30 | (0.98-1.71) | 0.0675 |
| Baseline total health care costs (per $1,000) | 1.02 | (0.97-1.06) | 0.4687 | 1.01 | (0.99-1.04) | 0.3015 |
| Erlotinib out-of-pocket costs per prescription (per $100) | 0.94 | (0.91-0.97) | 0.0001 | 1.17 | (1.14-1.19) | 0.0001 |
| Histology (squamous cell vs. adenocarcinoma) | 1.18 | (0.71-1.98) | 0.4695 | 0.98 | (0.73-1.31) | 0.8690 |
| Histology (other vs. adenocarcinoma) | 0.96 | (0.52-1.79) | 0.6979 | 0.83 | (0.58-1.18) | 0.3000 |
| Staging (stage IV vs. not stage IV) | 1.59 | (1.03-2.44) | 0.0355 | 0.91 | (0.72-1.14) | 0.4128 |
Note: Adherence Model=Intercept Only: -2 log likelihood 654.497; Full Model: -2 log likelihood 605.258 c2=41.9666 df=20, P=0.0028; c=0.685. Persistence Model=Intercept Only: -2 log likelihood 3603.773; Full Model: -2 log likelihood 3428.987 c2=174.7860 df=21, P≤0.0001.
aPatients with chart data, n=572.
bAdherence defined as medication possession ratio > 80%.
CI = confidence interval; df = degrees of freedom; HR = hazards ratio; IV = intravenous; NSCLC = non-small cell lung cancer; OR = odds ratio.