Abstract PD8-09: Predicted financial impact of continued HER2-directed therapy in metastatic breast cancer: What is the financial toxicity in a public payer healthcare system?
Authors: Jackson Emily B , Corke Lauren , Ohm Hyejee , Simmons Christine 
Published: March 2022

Abstract
Background Continued HER2 suppression in metastatic breast cancer (MBC) has been demonstrated to improve progression free survival (PFS) and overall survival (OS) in many randomized studies to date. Current funding policy in British Columbia (BC) restricts to two lines of HER2 directed therapy (HER2Rx) in MBC. With the development of novel HER2Rx agents, accessing continued HER2 suppression in the MBC has become complex. The financial implications of adapting future funding policies to reflect increasing lines of proven HER2Rx is unknown. Purpose The purpose of this study is to assess the proportion of patients with HER2 positive MBC eligible to receive systemic therapy beyond 2 lines of HER2Rx. We also wished to assess the proportion of eligible patients who accessed continued HER2Rx despite lack of public funding, and how their treatment beyond second line was funded. Methods The BC outcomes unit collects clinical and outcome information on 85% of all patients diagnosed with in the province of BC. In addition, all anti-neoplastic therapy delivered in the province is recorded in the BC Cancer pharmacy database. These two databases with queried and cross referenced to identify patients who received any HER2Rx for MBC dispensed by BC Cancer between 2013 and 2018, in the era where trastuzumab plus pertuzumab and TDM-1 were standard options and publically available. The number of lines of therapy received, specific treatments, and fitness to continue therapy beyond two lines were analyzed through targeted chart review. PFS and OS data were also analyzed. Expected financial implications were calculated based on current cost of most commonly used therapies in the third line. Results We identified 230 patients who met inclusion criteria with detailed information about treatment at the time of analysis. 51% (117) of these patients were eligible to continue therapy beyond second line. Of these, 86 (37% of the whole cohort) did access continued HER2-directed therapy, while 26 (11% of the whole cohort) were eligible but unable to access continued HER2Rx. The remaining 49% of were not eligible for consideration of further HER2Rx due to either stable disease on current treatment or deterioration precluding further treatment. The median lines of therapy in the entire study population was 3. Minimum lines of therapy was 1, maximum number of lines of therapy delivered was 12. Median number of cycles of therapy received beyond second line for those eligible to continue treatment was 22 cycles. Median OS for those who continued HER2Rx was 58.6 months compared to 38.0 months for those who were eligible but did not continue therapy, but this was not statistically significant (p = 0.13). The vast majority of these patients are receiving continued HER2Rx through either exceptional access or clinical trial, and very rarely through private pay or insurance. Conservative estimated cost per cycle of HER2Rx was based on currently available biosimilars to Trastuzumab. If these trends in survival continue we would expect an additional cost of $44000 per patient over current costs. Conclusion 51% of patients with HER2 positive MBC are eligible to receive more than two lines of HER2 directed systemic therapy. Of these eligible patients, the majority of patients (77%) are accessing treatment despite prohibitive funding policies, based on clinical trial or compassionate access programs. As funding policies adapt to the evolving treatment landscape for patients with HER2 positive MBC, we can expect a significant increase in cost per patient in this setting with conservative estimates of $44000 per patient above current costs. As the cost of novel therapies are likely to be higher than currently available biosimilars, there will be significant implications for both private payer and public payer healthcare systems.
Citation Format: Emily B Jackson, Lauren Corke, Hyejee Ohm, Christine Simmons. Predicted financial impact of continued HER2-directed therapy in metastatic breast cancer: What is the financial toxicity in a public payer healthcare system? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD8-09.