Liquid vs Tissue Biopsy Concordance in Samples of 1st Suspected BCa Recurrence/Metastasis and Evaluation of DefineMBC Comprehensive Cancer Profiling Liquid Biopsy LDT

An estimated 287,850 women will be diagnosed with invasive breast cancer in the US in 2022 (cancer.org). Most women with breast cancer present with disease confined to the breast and local lymph nodes, where surgical removal of lesions is standard of care and well-managed. Those diagnosed and treated for primary breast cancer often recur with metastatic disease more than 5 years after initial diagnosis. (Pan, NEJM 2017).

Sadly, when lesions emerge in other areas, after months or decades with no evidence of disease, mortality rates rise. The most common sites of distant recurrence of breast cancer are the bone, lung, liver, and brain, (Lin, NCCN 2012), all of which are difficult to biopsy, and obtain pathological evidence of malignancy because metastatic lesions: 1) are not always accessible/deeply located, 2) are prone to under sampling, and 3) may present dense fibrotic tissue. In addition, tissue biopsy methods in metastatic lesions have been shown to:

1. have low patient compliance,
2. have high discordance rate with malignant lesions at imaging,
3. be incompatible with longitudinal monitoring.

As a result, at a critical point in patient care, there is still a current unmet need for diagnostic information to guide decision-making.

As established widely in published literature over the past decade, receptor status often changes between primary and metastatic disease, and during lines of metastatic treatments, changing the trajectory of the disease and further highlighting the need for longitudinal evaluation of receptor status. Occult micro-metastases or minimal residual disease (MRD) cannot be detected with current medical modalities and can originate metastatic relapse at distant sites. For this reason, cellular and molecular liquid biopsy approaches that enable detection of disease relapse allow therapy escalation many months earlier than overt relapse detected by imaging which as result may increase patients' survival. Based on discussions, interviews, and surveys of both thought-leading academics and community-based medical oncologists, there is an evident opportunity to improve patient care. Moreover, the market shows receptivity to a blood-based test for these inaccessible cases as well as improve identification of patients at high risk of relapse or eligible for earlier treatment escalation compared to current tissue biopsy testing in practice today.