Colorectal cancer: what if a blood test were enough?

By Ana Espino | Published on March 11, 2026 | 3 min read


Colorectal cancer (CRC) remains the third most common cancer worldwide, accounting for nearly 10% of all cancers. Despite the effectiveness of screening with fecal immunochemical tests and colonoscopy, diagnosis and monitoring still rely largely on invasive techniques that can be burdensome for patients.  

The transition toward precision oncology requires tools capable of reflecting tumor dynamics in real time. Liquid biopsy, based on the analysis of circulating biomarkers in blood, has emerged as a promising alternative. It mainly relies on three categories: circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and exosomes.  

This review, published in 2025 in the Polish Journal of Surgery, analyzes the clinical contribution of these biomarkers in the diagnosis, prognosis, and therapeutic monitoring of CRC, comparing their performance and limitations with conventional methods.  

What does patients’ blood really reveal?   

The authors provide a structured synthesis of the clinical applications of the three main liquid biopsy markers.  

Circulating tumor DNA (ctDNA) originates from cancer cells through apoptosis, necrosis, or active secretion. It accurately reflects the tumor’s genetic profile, including key mutations such as KRAS, APC, TP53, BRAF, NRAS, or PIK3CA. ctDNA enables the detection of minimal residual disease (MRD) after surgery, early identification of recurrences, and real-time monitoring of responses to chemotherapy or targeted therapies. Quantitative changes in ctDNA correlate with tumor progression and treatment efficacy. Analysis of methylation patterns further improves diagnostic specificity.  

Exosomes, extracellular vesicles rich in RNA, proteins, and lipids, provide a complementary view of the tumor microenvironment. MicroRNAs such as miR-21 and miR-135b are associated with tumor aggressiveness and metastasis. Exosomal proteins such as CEA or EpCAM help differentiate benign from malignant lesions. Their biological stability and role in intercellular communication reinforce their potential as dynamic biomarkers.  

Circulating tumor cells (CTCs) represent cells that have detached from the primary tumor. Their detection, using markers such as EpCAM, CK20, or CD133, allows assessment of metastatic potential. An increased number of CTCs is associated with more aggressive disease and poorer prognosis. Molecular characterization of these cells may reveal mutations responsible for therapeutic resistance.  

However, several technical limitations remain. Detection of ctDNA may be affected by clonal hematopoiesis of indeterminate potential (CHIP), which can generate false positives. Standardization of analytical methods remains essential to ensure clinical reproducibility.   

Toward blood-guided oncology  

Colorectal cancer requires monitoring tools that are precise, sensitive, and minimally invasive. This review aimed to evaluate the potential of liquid biopsy markers in the management of CRC.

Available data confirm that ctDNA, exosomes, and CTCs enable dynamic and personalized disease monitoring, with a unique capacity to reflect tumor heterogeneity in real time. Their use could optimize early detection of recurrences, guide therapeutic strategies, and improve prognosis.  

However, widespread clinical integration requires rigorous methodological standardization, prospective validation, and the development of international guidelines. In the long term, liquid biopsy could become a central pillar of personalized medicine in colorectal oncology, transforming tumor monitoring into a continuous, precise, and less invasive process for patients.  



About the author – Ana Espino
PhD in Immunology, specialized in Virology  
As a scientific writer, Ana is passionate about bridging the gap between research and real-world impact. With expertise in immunology, virology, oncology, and clinical studies, she makes complex science clear and accessible. Her mission: to accelerate knowledge sharing and empower evidence-based decisions through impactful communication.