44 Drivers of Oncologist Treatment Selection in HR+/HER2- Metastatic Breast Cancer

Michael M. Gaschler, PhD¹; Qi Fu, PhD¹; Debanjali Mitra²; Samantha Kurosky²

¹Kantar, New York, NY

²Pfizer Inc, New York, NY

Background

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) are a recommended standard of care for many first-line (1L) hormone receptor–positive, HER2-negative (HR+/HER2-) advanced/metastatic breast cancers (mBC). Yet, substantial use of 1L ET monotherapy and chemotherapy (CT) regimens have been observed. This study sought to understand United States (US) physician perspectives on clinical, economic, and institutional factors that inform 1L mBC regimen selection.

Methods

We recruited 23 US oncologists treating patients with HR+/HER2- mBC for 45-minute, qualitative, one-on-one telephone interviews. Physicians were selected based on self-reported 1L patient volume and prescribing behaviors. Self-reported 1L prescribing behavior was used to sort physicians into 1 of 3 cohorts: “high CDK4/6i prescribers,” “high ET monotherapy prescribers,” or “high CT prescribers.” Physicians were not aware of their cohort, and all interviews were conducted based on the same discussion guide. Discussions were coded and analyzed using a thematic approach with the MAXQDA (v12.0) software.

Results

All cohorts reported high use of 1L CDK4/6i plus ET regimens and ranked clinical data as the primary driver of regimen selection. However, each cohort identified unique treatment-level, patient-level, and nonclinical factors that influenced 1L regimen choice. The high CDK4/6i cohort (n = 5) considered CDK4/6i plus ET regimens to be appropriate for nearly all 1L patients, seldom relying on nonclinical factors to guide treatment. The high ET-monotherapy cohort (n = 10) valued a perceived balance of efficacy and tolerability achieved with ET-monotherapy regimens, particularly for elderly patients. This cohort reported their patients faced affordability challenges with CDK4/6i, describing greater difficulties resolving cost issues. High CT prescribers (n = 8) valued a perceived fast response and high compliance rate with CT. High CT prescribers also indicated patient comorbidities influenced regimen selection.

Conclusions

All cohorts recognized CDK4/6i plus ET regimens as the preferred standard of care for most patients, but perceptions of the appropriateness of 1L regimens varied across cohorts. Continued demonstration of CDK4/6i plus ET safety and effectiveness across broader patient populations in real-world settings may provide the additional evidence needed to support appropriate 1L treatment selection.