Clinical and economic benefit of genomic testing strategies to guide the treatment of patients with HR+/HER2- breast cancer in the US.

10584 Background: Multiple testing technologies are available to inform treatment decisions for hormone receptor positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-) early-stage breast cancer, including tumor profiling and germline genetic testing (GGT). The 21-gene assay provides an estimate of distant recurrence risk and potential clinical benefit of chemotherapy. GGT identifies pathogenic variants which inform lifetime cancer risk as well may inform therapy options. This study explored the potential synergy of utilizing both tests by assessing the cost-effectiveness of this strategy compared to no testing from a societal perspective. Methods: A health economic model was developed using best practices to assess a patient cohort with HR+/HER2-, node-negative (N0) or node-positive (N1) breast cancer that was guided to surgical and adjuvant treatment by GGT (ATM, BRCA1/2, CDH1, CHEK2, PALB2, PTEN, and TP53) and the 21-gene assay. Treatment effectiveness was informed by clinical trials (TAILORx and RxPONDER) ; costs for treatment, monitoring, and health utilities were sourced from literature. Clinical expert opinion and guidelines informed current US clinical practice. The base case analysis evaluated lifetime total costs, life-years, and quality-adjusted life years (QALYs) versus no testing. Scenario and sensitivity analyses were performed to evaluate model robustness. Results: The testing strategy was dominant (lower cost and higher QALYs gained) compared to no testing leading to a QALY improvement of 0. 286 and cost savings of 16, 463 in the N0 population (Table) and a 0. 099 QALY improvement and 299 cost savings in the N1 population. Scenario analyses indicated that while the 21-gene assay was the primary driver of results, there were synergistic effects when tests were combined. Sensitivity analysis supported cost-effectiveness at most willingness-to-pay thresholds and identified the probability of chemotherapy and rate of distant recurrence as the most impactful model inputs. Conclusions: Using a testing strategy including both the 21-gene assay and GGT enables optimization of treatment decisions in early HR+/HER2- breast cancer, improving patient outcomes at reduced costs. Table: see text