Abstract P4-07-47: Real-world practice patterns in the management of metastatic breast cancer in Washington State
Authors: Manohar Poorni , Linden Hannah , Shankaran Veena , Fedorenko Catherine , Voutsinas Jenna , Sun Qin , Wu Vicky 
Published: March 2023

Abstract
Background: Evidence-based recommendations for the management of metastatic breast cancer (MBC) endorse confirmation of recurrence with biopsy and reassessment of biomarker status. National guidelines support numerous treatment options and do not capture the nuances of real-world practice. Real world data may demonstrate disparities in adherence to guidelines.
Methods: We collaborated with Hutchinson Institute for Cancer Outcomes Research (HICOR) to link enrollment and insurance claims records with Washington State cancer registries from 2008-2017. Our cohort comprised of women &gt; 18 years old with MBC who met enrollment criteria in one of four payors (Premara, Regence, Medicare, or Medicaid). We identified receipt of biopsy and biomarker re-assessment at time of recurrence, receipt of first line treatment, categorized as CDK4/6 inhibitors (CDKi), chemotherapy (CT), or hormone therapy (HT) and examined factors influencing these practice patterns.
Results: We identified 1,101 patients with MBC (recurrent MBC, N = 715; de novo MBC, N = 386) with a median age of 66 (range 54 – 74). Of the patients with MBC, there were a total of 677 patients with ER+/HER2- MBC. Table 1 shows demographic data. Most of the cohort were White (89%). Approximately 15% of patients lived in areas of high deprivation (area of deprivation index, ADI, 8-10). Patients had either Commercial (47%), Medicaid (4%), Medicare (35%) or multiple (13%) insurance. Of the patients with recurrent MBC, 49.5% received a biopsy to confirm metastatic diagnosis. Similarly, 48.7% of recurrent MBC patients underwent biomarker reassessment. Patients with highest co-morbidity index (2) were more likely to undergo biopsy confirmation (20.3% vs 13.0%, p = 0.02). Biopsy was more often performed at recurrence in patients receiving care at a high-volume center (74.3% vs 67.6%, p = 0.03) compared to low volume center (18.6% vs 26.6%, p = 0.03). First line treatment selection was directly associated with receipt of biopsy and biomarker testing. Hormone therapy only was more common in patients who did not undergo biopsy (62.3% vs 37.7%, p &lt; 0.001) or biomarker reassessment (62.7% vs 37.3%, p &lt; 0.001). Of the patients with ER+/HER2- MBC, the majority of patients received ET alone (69%), followed by chemotherapy (22%), and CDK4/6i + ET (9%). Dual agent CT was the more commonly prescribed compared to single agent in those who received CT (56% vs 44%). The majority of patients who received CDKi + ET were &lt; 65 years old (65.2%, p &lt; 0.02). Insurance influenced first line therapy selection and patients with commercial insurance were more likely to receive CDK4/6i + ET compared to those with Medicare/Medicaid. (60.9% vs 26.1%, p = 0.10). Patients with de novo MBC were more likely to receive CT (43.1% vs 13.4%, p &lt; 0.001) and less likely to receive ET alone (47.9% vs 78.0%, p &lt; 0.001). Almost all patients treated with CDK4/6i + ET received care a high-volume center (91.3%, p = 0.11).
Conclusion:Our findings highlight key gaps for future investigations in the management of MBC and serve as a launching point for new patient-centered and quality-promoting research initiatives.
Table 1: Baseline Demographics 1# of patients treated annually, high = &gt;100, medium 25-100, low &lt;25.
Citation Format: Poorni Manohar, Hannah Linden, Veena Shankaran, Catherine Fedorenko, Jenna Voutsinas, Qin Sun, Vicky Wu. Real-world practice patterns in the management of metastatic breast cancer in Washington State [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-47.