Blood tests called liquid biopsies can detect circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs). CTCs are tumor cells that came from a tumor and are now moving (circulating) through the blood. ctDNA are small pieces of DNA from cancer cells that are released into the blood. In clinical trials, researchers are studying what ctDNA and CTC testing results can tell them about MBC and how to treat it.
Click the links below to learn more about these blood tests and how they are being used in MBC.
Introduction to ctDNA and CTC Testing
- Medline Plus: ctDNA is found in the blood and can be used to detect cancer, guide treatment decisions, and monitor response to treatment
- Living Beyond Breast Cancer: The amount of CTCs in the blood may help find out if cancer is spreading or not responding to treatment
- Cancer Today: Liquid biopsy results come back faster than tissue biopsy results and can be used when a tissue biopsy can’t be done or doesn’t give clear answers
Research on CTC Testing for MBC
- Breast Cancer (journal article): High numbers of CTCs predict a poor outcome in MBC. Using CTC testing to select treatment in MBC is an active area of research in clinical trials
Research on ctDNA Testing for MBC
- ASCO Post: Clinical trial results presented at ASCO 2025 show that survival outcomes may improve when both tissue and liquid biopsies are used to make treatment decisions
- Living Beyond Breast Cancer: Results from the SERENA-6 clinical trial presented at ASCO 2025 show that switching to camizestrant after detecting an ESR1 mutation using ctDNA testing improves MBC outcomes
Standard of Care for ctDNA Testing in MBC
- Breastcancer.org: ctDNA testing can find mutations that are only in cancer cells and can help select treatments
- Breastcancer.org: ctDNA testing for a mutation in ESR1 can help select treatment with elacestrant (Orserdu®) in estrogen receptor-positive MBC
- Breastcancer.org: ctDNA testing for a mutation in PIK3CA can help select treatment with alpelisib (Piqray®) in hormone receptor-positive MBC
- Oncology Nursing News: ctDNA testing for mutations in HER2 can help select treatment with neratinib (Nerlynx®) in HER2-positive MBC
MBC Clinical Trials
- Metastatic Trial Search: Trials for CTC Testing
- Metastatic Trial Search: Trials for ctDNA Testing
- Metastatic Trial Search: Trials for Genetic and Biomarker Testing
Last Modified on July 7, 2025