Assessing functional status and the survival benefit of chemotherapy for advanced non-small cell lung cancer using administrative claims data

Objectives: Borderline or poor performance status (PS) patients comprise a significant proportion of those diagnosed with advanced non-small cell lung cancer (AdvNSCLC), but are often excluded from clinical trials. It is difficult to draw conclusions about the benefit of therapy in borderline PS patients due to lack of reliable PS assessments, and small clinical trial samples. Retrospective population-based secondary analyses may allow investigators to study under-represented populations in clinical trials. We hypothesized that patients with poor functional status derive benefit from chemotherapy compared good functional status, but that the magnitude of the benefit is lower compared to patients with good functional status. By utilizing a "disability status" (DS) measure as a proxy for PS, we offer a reliable mechanism for patient stratification that can be implemented in administrative claims data. Methods: Medicare beneficiaries diagnosed with AdvNSCLC between 2001 and 2005 were selected from the Surveillance, Epidemiology and End Results database linked to Medicare claims. Disability status, a previously developed and validated claims-based proxy for baseline PS, was implemented. Patients were assigned to good versus poor DS. Cox proportional hazard models were used to examine the differential effects of chemotherapy for the two DS groups on all-cause mortality, controlling for tumor and patient characteristics. Results: Most patients in the cohort (n=21,019) were ≥75 years of age (59%), and non-Hispanic white (85%); 91% were assigned to good DS; 38% received chemotherapy. Chemotherapy had a strong protective effect among good DS patients (hazard ratio, 0.43; CI 0.42-0.45; p < 0.001), with a slightly smaller effect for poor DS (hazard ratio, 0.50; CI 0.44-0.57). Conclusions: Chemotherapy improves survival for advanced NSCLC patients with poor DS but to a lower magnitude than for good DS patients. The DS measure opens the door to assess outcomes for cancer patients with poor functional status using insurance claims data.