Background: The use of molecularly-directed targeted therapies has become a vital tool in treating advanced breast cancer patients. While solid tumor testing is standard of care for biomarker detection, the use of circulating tumor DNA (ctDNA), a noninvasive technology for molecular profiling is becoming more common. Concurrent testing, or the use of simultaneous solid tissue and ctDNA testing, has the potential to increase detection of actionable findings, as well as reduce adverse events from repeat biopsies compared to solid tissue testing alone. A large real-world study of patients tested concurrently identified an additional 20% of patients with advanced breast cancer with actionable findings which were missed by tissue-based testing alone. We use these data to assess the economic impact of concurrent testing compared to tissue-only testing in a simulation of patients with advanced Breast Cancer in the United States.

Methods: This microsimulation compares concurrent testing to solid tumor testing alone in patients with advanced breast cancer. Frequency of actionable biomarkers (BRCA1, BRCA2, ERBB2, ESR1, PIK3CA, and MSI) detected by testing modality were derived from a real-world data study of patients tested concurrently. Other model inputs, including detection rates of testing modalities, rates of rebiopsy due to inadequate tissue, and rates of adverse events were derived from literature. Total costs modeled included cost of NGS, biopsy costs, and management of adverse events due to biopsies. We assumed the cost of solid tumor and the cost of liquid biopsy were each $2,919. The primary economic endpoint measured was the total cost per patient, while the primary clinical endpoints included percentage of patients with actionable variants identified, total biopsies performed per cohort, and serious biopsy events avoided per cohort.

Results: In a simulated cohort of 1,000 patients, real-world data suggest that 587 patients will carry an actionable variant. In the model simulations, concurrent testing identified 93 more patients with actionable findings than solid tumor testing alone (586 patients detected via concurrent testing vs. 493 patients detected by solid tumor testing), while also reducing the number of additional biopsies by 24. This reduction translates to a number needed to test (NNT) with concurrent testing to prevent one additional biopsy of 42 patients.The improved outcomes came at an increased incremental cost per patient of concurrent testing of $2,803 ($6,853 compared to $4,050 for solid tumor testing alone), $106 less than the cost of an additional liquid biopsy test.

Conclusions: Concurrent testing in advanced breast cancer identifies a higher proportion of patients with actionable variants than tissue testing alone, at a per-patient cost that is less than the actual cost of the liquid biopsy. This increased identification, coupled with a reduction in repeat biopsies, highlights a role for concurrent testing in the management of advanced breast cancer.

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