Despite new treatment options and advances in patient management protocols, research shows that between 15% and 30% of women initially diagnosed with earlier stages of breast cancer are at risk of developing recurrent advanced or metastatic disease. Although the prognosis of patients with metastatic breast cancer (MBC) has significantly improved, the 5-year survival rate for breast cancer patients with metastases is just 31%. Advancements in biopsy methodology for MBC are needed to improve patient monitoring and survival.

The UK National Health Service (NHS) follows the National Institute of Health (NICE) guidelines which recommends a core or needle biopsy along with physical examination and imaging (mammogram, ultrasound) to diagnose breast cancer. The most recent ESMO clinical practice guidelines for diagnosis, staging and treatment of MBC patients also recommend that patients with newly diagnosed or recurrent MBC should undergo a tissue biopsy. Solid tissue biopsy confirms malignancy and tumour tissue receptor status which is clinically relevant to determine breast cancer subtype, clinical prognosis, and the choice of targeted therapy. However solid tissue biopsy is invasive, costly, time-consuming, potentially harmful, and is unsuitable for longitudinal monitoring. Tumour tissue may also be inaccessible or report a false negative if an insufficient sample is taken.