cell-free tumour DNA

Overview

Cell-free tumour DNA, more commonly referred to as circulating tumor DNA (ctDNA), is the tumour-derived fraction of cell-free DNA found in body fluids, especially blood plasma and, in some settings, cerebrospinal fluid. It consists of short DNA fragments released from cancer cells through apoptosis, necrosis, and active secretion, and it carries somatic alterations such as point mutations, copy-number changes, structural variants, and DNA methylation patterns that reflect the genomic and epigenomic state of the tumour.

Clinically, ctDNA is a major liquid biopsy analyte because it can be sampled noninvasively and repeatedly over time. It is being investigated for detection of minimal residual disease, prognosis, treatment selection, monitoring of response, and early identification of resistance or tumour evolution. Its utility is particularly relevant in cancers such as breast cancer, colorectal cancer, non-small cell lung cancer, prostate cancer, melanoma, bladder cancer, esophageal squamous cell carcinoma, and diffuse glioma, where tissue-free molecular profiling may complement or, in some contexts, substitute for tissue-based testing.

Focus of Latest Publications

Recent publications have continued to position ctDNA as a dynamic biomarker across multiple tumour types and treatment settings. In hormone receptor-positive, HER2-negative advanced breast cancer treated with first-line ribociclib and letrozole, baseline and longitudinal ctDNA were evaluated for prognostic and predictive value in the BioItaLEE trial, indicating interest in how ctDNA may refine outcome prediction during endocrine-based therapy. In a separate breast cancer context, ultrasensitive ctDNA assessment was studied for minimal residual disease (MRD), with the Pathologic Response Evaluation and Detection in Circulating Tumor-DNA study suggesting that ctDNA-based MRD assessment may provide additional or superior risk stratification after treatment.

In colorectal cancer, ctDNA was examined in several ways. One study reported that circulating tumor DNA methylation level was a more accurate prognostic biomarker in colon cancer, including analysis of SOX11 methylation in ctDNA and its correlation with metastatic lymph node burden. Another study in metastatic colorectal cancer assessed ctDNA dynamics during cetuximab-based induction and maintenance treatment in the TIME-PRODIGE-28 trial, asking whether changes in ctDNA could help assess clinical outcomes. In adjuvant colon cancer, the Alliance N0147 trial evaluated tissue-free ctDNA assays for detection of molecular residual disease and their association with patient outcome, supporting postoperative risk stratification and potential guidance of adjuvant therapy. A review of practice-changing gastrointestinal cancer trials also highlighted ctDNA-guided de-escalation strategies, including the ESMO 2025 DYNAMIC-III trial, as an emerging approach to reduce toxicity while maintaining outcomes.

In lung cancer and thoracic malignancies, ctDNA was used for noninvasive mutational profiling and disease characterization. A study in advanced non-small cell lung cancer described plasma cell-free DNA sequencing, including the tumour-derived ctDNA fraction, as a means of comprehensive genomic profiling by next-generation sequencing. Another review on EGFR-mutant non-small cell lung cancer discussed circulating tumor DNA guidance in the context of acquired resistance to third-generation EGFR tyrosine kinase inhibitors and the broader development of antibody-drug conjugates such as amivantamab. In cadmium-related lung toxicity and carcinogenesis, cfDNA/ctDNA and methylation were included among multi-omics signals used to study inflammation, oxidative stress, and carcinogenic pathways.

In prostate cancer, ctDNA was repeatedly linked to prognosis, tumour evolution, and treatment monitoring. One study in metastatic castration-resistant prostate cancer characterized longitudinal molecular changes in ctDNA and emphasized that ctDNA next-generation sequencing complements tissue-based testing for prognosis, treatment selection, and tumour evolution. Another study reported that pathogenic genomic alterations in ctDNA predict overall survival in men with metastatic castrate-resistant prostate cancer, including genomic biomarkers such as ctDNA aneuploidy and pathogenic genetic alterations. A protocol for patients receiving prostate-specific membrane antigen radioligand therapy described ctDNA as part of a prospective longitudinal liquid biopsy strategy to assess tumour heterogeneity, monitor response, and detect emerging resistance, in the setting of [177Lu]Lu-PSMA-617 and related Targeted Cancer Therapy. A phase II study of olaparib and durvalumab also incorporated longitudinal ctDNA analysis alongside immune profiling and PBMC gene expression profiling, reflecting interest in integrating ctDNA with immunotherapy and DNA repair-targeted treatment such as BRCA2 DNA repair associated pathways.

In neuro-oncology, ctDNA in cerebrospinal fluid was used to guide molecular reclassification of diffuse glioma patients. This work underscored that CSF ctDNA remains underutilized in clinical practice because of technical challenges, but it may be especially informative when plasma ctDNA is limited by the blood-brain barrier. In melanoma, an international expert survey described ctDNA as a promising biomarker with higher sensitivity for tumour burden detection than conventional diagnostics, reflecting growing consensus around its role in surveillance and response assessment.

Across other disease areas, ctDNA was also framed as a biomarker for MRD and treatment adaptation. In Hodgkin lymphoma, the German Hodgkin Study Group HD21 trial assessed MRD using a validated ctDNA sequencing assay, with the study noting that ctDNA-based MRD assessment is promising but dependent on standardized sampling time points, assay validation, and definitions of MRD negativity. In rectal cancer and esophageal squamous cell carcinoma, reviews highlighted ctDNA as a critical biomarker for MRD and as a dynamic marker that may refine perioperative patient selection and precision treatment strategies in the immunotherapy era. In bladder cancer, circulating biomarkers reviews placed ctDNA alongside exosomes and circulating tumor cells as emerging tools for diagnosis, prognosis, and treatment guidance.

Several studies also focused on assay development and analytical sensitivity rather than direct clinical outcomes. A CRISPR/Cas12a-driven electrochemiluminescent biosensor using a covalent organic framework-confined CsPbBr3 nanocomposite was developed for ultrasensitive ctDNA detection. Another analytical chemistry study used multiselective recognition of metal ion-nucleic acid complexes by CRISPR/Cas12a and quantum dots to profile ctDNA in breast cancer. A disposable CRISPR-nanozyme electrochemical biosensor was also reported for rapid and sensitive detection of breast cancer ctDNA. These studies reinforce the technical push toward low-cost and highly sensitive biosensor platforms for ctDNA measurement.

Key Publications

• Jun Role of ctDNA in Predicting the Outcome of Patients with Hormone Receptor-Positive, HER2-Negative Advanced Breast Cancer Treated with First-line Ribociclib and Letrozole: BioItaLEE Trial. (Clinical cancer research : an official journal of the American Association for Cancer Research, 2026, PMID 41587113): "...the prognostic and predictive value of baseline and dynamic circulating tumor DNA (ctDNA)..."
• Jun COF-confined CsPbBr3 nanocomposite with CRISPR/Cas12a-driven DNA walking for ultrasensitive electrochemiluminescent detection of circulating tumor DNA. (Biosensors & bioelectronics, 2026, PMID 41707429): "A highly sensitive electrochemiluminescence biosensor was developed for circulating tumor DNA detection by integrating a covalent organic framework-confined CsPbBr3 nanocomposite with a CRISPR/Cas12a-driven amplification strategy."
• Jun Circulating Tumor DNA Methylation Level Is a More Accurate Prognostic Biomarker in Colon Cancer. (Anticancer research, 2026, PMID 42203320): "We investigated the correlation of sizes of metastatic LNs with levels of methylation of the SOX11 gene in circulating tumor DNA (ctDNA)."
• May Somatic mutation profiling by NGS-based liquid biopsy in advanced non-small cell lung cancer: frequency, clinical correlates, and prognostic significance. (Molecular biology reports, 2026, PMID 42176127): "Liquid biopsy-based next-generation sequencing (NGS) of plasma cell-free DNA (cfDNA) - including its tumour-derived fraction known as circulating tumor DNA (ctDNA) - enables non-invasive, comprehensive mutational profiling in advanced non-small cell lung cancer (NSCLC)."
• May CSF ctDNA analysis guides molecular reclassification of diffuse glioma patients. (Journal of neuro-oncology, 2026, PMID 42168657): "However, the analysis of circulating tumor DNA (ctDNA) in cerebrospinal fluid (CSF) from patients with gliomas remains underutilized in clinical practice due to technical challenges."
• May Tissue-Free Circulating Tumor DNA Assay and Patient Outcome in a Phase III Trial of FOLFOX-Based Adjuvant Chemotherapy (Alliance N0147). (Journal of clinical oncology : official journal of the American Society of Clinical Oncology, 2026, PMID 41616224): "Detection of molecular residual disease using circulating tumor DNA (ctDNA) may enable postoperative risk stratification and guide adjuvant therapy."
• May Characterizing Longitudinal Molecular Changes in ctDNA in Patients with Metastatic Castration-Resistant Prostate Cancer. (Clinical cancer research : an official journal of the American Association for Cancer Research, 2026, PMID 41746190): "Circulating tumor DNA (ctDNA) next-generation sequencing complements tissue-based testing and offers insights into prognosis, treatment selection, and tumor evolution."
• May Translating ctDNA into cutaneous melanoma care: An international expert survey. (European journal of cancer (Oxford, England : 1990), 2026, PMID 41932032): "Circulating tumor DNA (ctDNA) is a promising biomarker in melanoma, with higher sensitivity for tumor burden detection than conventional diagnostics."
• May Circulating Tumor DNA Dynamics and Clinical Outcomes in Patients with Advanced Colorectal Cancer Treated with Cetuximab-Based Induction and Maintenance Treatment. (Clinical cancer research : an official journal of the American Association for Cancer Research, 2026, PMID 41671078): "We investigated whether circulating tumor DNA (ctDNA) changes may be useful to assess clinical outcomes in patients with metastatic colorectal cancer (mCRC) randomized in the TIME-PRODIGE-28 trial comparing biweekly maintenance with cetuximab alone with observation after 4-month fluorouracil, folinic acid, and irinotecan (FOLFIRI) plus cetuximab induction chemotherapy."
• May Multiselective Recognition of Metal Ion-Nucleic Acid Complexes by CRISPR/Cas12a and Quantum Dots Enables the Profiling of Circulating Tumor DNA in Breast Cancer. (Analytical chemistry, 2026, PMID 42027134): "The rapid, noninvasive detection of circulating tumor DNA (ctDNA) is vital for the diagnosis and staging of breast cancer (BC)."