A Registry-Based Study of Patterns of Use of Targeted Therapies for Metastatic Cancers in Diverse Populations

One of the most important cancer care advances in recent history is the rapid dissemination of targeted therapies (molecularly targeted kinase inhibitors and immune checkpoint inhibitors) into the care of patients with metastatic cancer. The marked expansion of indications for use of these novel therapies has been fueled

by growing enthusiasm among medical oncologists regarding their potential impact on survival for patients with very poor prognosis. Although the survival benefit of these therapies is modest for most patients, a small proportion experience long-term remission and potentially even cure of previously incurable cancer. Despite

the exciting promise of these therapies, they are very expensive – sometimes exceeding $10,000 per month. Because of the high cost and high stakes of these therapies, it is critical to understand their patterns of use; yet very little is known about targeted therapy use across diverse populations. Moreover, the impact of clinician

factors on variations in use is not known. In the absence of such knowledge it is difficult to develop effective interventions to support equitable delivery of these therapies to the growing population of patients living with metastatic cancer. Therefore, we will investigate patterns of use of targeted therapy among a diverse sample

of 2,240 patients diagnosed in 2019 with metastatic non-small cell lung cancer, genitourinary cancer, and melanoma, and ascertained by the Georgia and Los Angeles county SEER registries. We will first characterize patient factors associated with non-receipt, by creating a powerful combination of archival clinical and

sociodemographic registry data augmented with additional treatment data that SEER staff will collect directly from clinicians and practices. We hypothesize that significant variations exist in patient use of targeted therapy across age, race/ethnicity, socioeconomic status, and geography. We will then identify clinician factors that are

associated with tendency to prescribe targeted therapy. Informed by qualitative data that we will collect through interviews with medical oncologists, we will survey the medical oncologists (clinicians) who treat these patients, including many who practice in resource-limited settings. We will assess clinicians’ knowledge & attitudes

about targeted therapy, ask specific details about their practice setting, and use clinical vignettes to measure their tendency to prescribe targeted therapy. We will survey 1025 clinicians and anticipate a 65% response rate, based on our prior work. We hypothesize that certain clinicians are less likely to prescribe targeted

therapy, including those with less knowledge around targeted therapy and those who practice in resource- limited settings. Finally, we will merge clinician data with patient data to quantify and explain the influence of clinicians on variations in patients’ use of targeted therapy. We hypothesize that most (>50%) of the variation

occurs at the clinician level, and that clinician knowledge and attitudes drive most of the variation. The findings from this study will inform the development of multilevel interventions to improve equitable receipt of targeted therapies across diverse patient populations and practice settings.