Evaluating Use of Biomarker Testing Among Patients with Advanced Non-Small Cell Lung Cancer

Among patients diagnosed with advanced non-small cell lung cancer (aNSCLC), biomarker testing is used to profile genetic mutations and protein levels in the individual’s tumor, enabling providers to match patients with the treatment best suited for their tumor type. The objective of this dissertation was to examine key aspects the real-world use of biomarker testing in clinical practice, and the three studies in this dissertation used cancer registry data linked with Medicare claims from 2009-2018 to: (1) evaluate racial disparities in the receipt of biomarker testing; (2) examine initiation of systemic therapy associated with biomarker testing; and (3) characterize survival outcomes associated with the chronological ordering of biomarker testing and systemic therapy. Biomarker testing was suboptimal with only 58.2% (n=15556) of patients receiving testing. Black patients were significantly less likely to receive biomarker testing than White patients (adjusted risk ratio [aRR]: 0.87; 95% confidence interval [CI]: 0.87-0.94). Receipt of biomarker testing was significantly associated with initiation of systemic treatment within six months of diagnosis (adjusted hazard ratio [aHR]: 1.45; 95% CI: 1.34-1.56). Among patients who had receipt of biomarker testing within three months of diagnosis and systemic therapy within six months of diagnosis, increased time to biomarker testing and clinical factors were predictors of preemptive initiation of systemic therapy (i.e., initiation of therapy prior to biomarker testing). Receipt of biomarker testing followed by initiation of systemic therapy was associated with lower all-cause (aHR: 0.78; 95% CI: 0.72-0.84) and lung cancer death (adjusted subdistribution hazard ratio [aSHR]: 0.84; 95% CI: 0.77-0.91) compared to no receipt of biomarker testing or initiation of systemic therapy. Preemptive initiation of systemic therapy was not associated with all-cause or lung cancer-specific survival benefit relative to no testing and no therapy. Findings from this dissertation suggest that barriers to receipt of testing need to be investigated for equitable access to biomarker testing-directed therapies, and that identifying reasons for preemptive treatment is necessary to ensure initiation of the most suitable first-line therapy. Collectively, these findings can inform development of interventions to ensure equitable, optimal and timely receipt of biomarker testing and testing-directed treatments for patients with aNSCLC.