Circulating Tumor Cells (CTCs) are:
Drivers of Metastasis
Drivers of Metastasis
CTCs are cells that detach from a tumor and travel through the bloodstream, seeding new tumors in distant organs.
Prognostic
Prognostic
High numbers of CTCs in the blood are associated with worse patient outcomes.
Present Across Disease Stages
Present Across Disease Stages
CTCs are detectable not only in advanced cancers but also in earlier stages.
Representative of Tumor Heterogeneity
Representative of Tumor Heterogeneity
Single cell CTC analysis can capture the diversity of cancer cell populations, including: epithelial, mesenchymal, and hybrid/EMT CTCs, plus CTC clusters which are known to be 100x more metastatic than single CTCs.
Intact and Viable Cells
Intact and Viable Cells
CTCs are intact, viable parts of a tumor that retain tumor DNA, RNA, and proteins allowing complete biological insight with genomic, transcriptomic, and proteomic analysis from a single blood draw. As viable cells they are suitable for cell culture and xenotransplantation.
A Minimally Invasive and Repeatable Sample
A Minimally Invasive and Repeatable Sample
CTCs can be analysed through a simple blood draw, enabling safer and more frequent sampling compared to tissue biopsies. Repeated CTC analysis allows tracking of molecular change, treatment response, and emerging resistance over time to support longitudinal monitoring.
Biology of Circulating Tumor Cells
CTCs are intact, viable cancer cells that detach from primary or metastatic tumors and enter the bloodstream. Unlike circulating tumor DNA (ctDNA), which consists of fragmented DNA released mainly from dying cells, CTCs remain whole. As whole cells CTCs carry genomic, transcriptomic, and proteomic information. CTCs are detectable not only in metastatic disease but also in earlier stages of cancer, contrary to the common perception that they appear only in advanced cases.
With advances in genomic sequencing, oncologists are increasingly able to select therapies based on the specific DNA mutations identified in a patient’s tumor. However, many patients fail to respond to targeted treatment or do not have a sustained response. That may be, in part, because key information about the biology of the tumor is missing from looking at the DNA alone.
While the presence of mutations can be determined from DNA, the effect of mutations on protein function cannot be fully understood without analyzing gene expression (RNA) and the proteins themselves. Understanding protein expression provides a more accurate and functional description of the tumor at the specific sampling time, and is critical for drug development, treatment selection, and predicting treatment response. This is recognized by the National Institute of Health as being crucial to improving patient outcomes.
There is growing understanding and investment into this multiomic assessment, which aims to provide the complete picture of a patient’s tumor and transform personalized medicine. As whole cells, CTCs allow us to look beyond the genome at complete DNA, RNA, and protein expression analysis for genomic, transcriptomic, and proteomic assessment.
CTCs Provide the Complete Genome, Transcriptome, and Proteome
20,000-25,000
Genes that are units of DNA that code for proteins.
~100,000
Transcripts to make proteins genes must be first transcribed into messenger RNA.
>1,000,000
Proteins shaped by modifications that influence function, activity, and lifespan.
References
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2. Obermayr, E. et al. Gene expression markers in peripheral blood and outcome in patients with platinum resistant ovarian cancer: A study of the European GANNET53 consortium. Int. J. Cancer ijc.34978 (2024).
3. Ring, A. et al. Circulating Tumor Cell Transcriptomics as Biopsy Surrogates in Metastatic Breast Cancer. Ann. Surg. Oncol. 29, 2882–2894 (2022).
4. Bayou, N. et al. Quantitative HER2 profiling on circulating tumor cells using an EpCAM-independent platform in metastatic breast cancer. Cancer Cell Int. 25, 439 (2025).
5. Markou, A. N. et al. Preoperative Mutational Analysis of Circulating Tumor Cells (CTCs) and Plasma-cfDNA Provides Complementary Information for Early Prediction of Relapse: A Pilot Study in Early-Stage Non-Small Cell Lung Cancer. Cancers 15, 1877 (2023).
6. Kurzeder, C. et al. Digoxin for reduction of circulating tumor cell cluster size in metastatic breast cancer: a proof-of-concept trial. Nat. Med. 31, 1120–1124 (2025).
7. Bowley, T. Y. et al A Melanoma Brain Metastasis CTC Signature and CTC:B-cell Clusters Associate with Secondary Liver Metastasis: A Melanoma Brain-Liver Metastasis Axis. Cancer Research Communications, 5(2), 295–308 (2025).
8. Nicolò, E. et al. International expert consensus on the clinical integration of circulating tumor cells in solid tumors. European Journal of Cancer, 231, 116050. (2025).