The ability to identify the molecular features of metastatic breast cancer
(BC) provides a unique insight into a patient's therapeutic options and the opportunity
to follow the BC progress over time. A classical tissue biopsy remains the standard
procedure to describe tumor biology and guide treatment choices.
However, a liquid biopsy, which can provide medical practitioners with the
opportunity to detect genomic mutations and monitor therapeutic effects, can play a
prominent role in the diagnosis, therapy, and prognosis of patients with different
malignancies, including metastatic BC. In fact, the liquid-biopsy-based therapeutic
interventions led to the approval of alpelisib (a PI3K inhibitor) in patients with
hormone receptor (HR)-positive, human epidermal growth factor receptor2
(HER2)-negative, advanced or metastatic BC, in whom BC had progressed on or
after therapy with an aromatase inhibitor (AI).
This chapter describes a liquid biopsy in BC. It explores its potential for clinical
applications in early diagnosis, monitoring treatment response, detecting minimal
residual lesions, predicting risk of progression or recurrence, and estimating
prognosis. It compares a liquid biopsy with a tissue biopsy, and outlines the benefits
and limitations of each of these procedures, focusing on patients with metastatic BC.
Moreover, this chapter analyses the results from recent studies relevant to liquid
biopsies in BC (e.g., circulating tumor cells (CTCs) and circulating tumor DNA
(ctDNA)).
Keywords: Alpelisib (A PI3K Inhibitor), Breast cancer (BC), Circulating tumor cells (CTCs), Circulating tumor DNA (ctDNA), Liquid biopsy, Targeted therapy.
