How to choose between CTC and ctDNA in cancer detection?
What is ctDNA?
Circulating tumor DNA (ctDNA) is small fragments of DNA released into the blood by cancer cells. These fragments carry genetic and epigenetic information associated with cancer, making them important biomarkers for cancer detection, treatment monitoring, and disease progression assessment.
Notably, ctDNA is not only detected in cancer patients, but also in healthy individuals and patients with benign tumors. ctDNA testing usually targets specific genetic alterations, such as mutations in oncogenes or tumor suppressor genes, to confirm that the detected DNA comes from tumor cells. Most ctDNA comes from cancer cells that have undergone apoptosis (programmed cell death) or necrosis (cell death due to damage or disease).

Application of ctDNA in cancer detection
- Tumor genetic analysis:
ctDNA reflects genetic changes in tumors, including mutations that may arise during treatment, helping to track tumor evolution and treatment effectiveness. - Mutation detection:
ctDNA testing can identify specific mutations associated with cancer, including mutations that can be used for targeted therapy, such as EGFR or KRAS gene mutations. - Treatment monitoring:
Changes in ctDNA levels can reflect the effectiveness of treatment. A decrease means that the treatment is effective, while an increase may indicate drug resistance or disease progression. - Early detection of recurrence:
ctDNA may detect cancer recurrence earlier than traditional imaging methods.
Limitations of ctDNA testing
ctDNA mainly comes from dead tumor cells and may not accurately reflect immediate tumor activity, especially in heterogeneous tumors.
ctDNA testing focuses on identifying specific mutations, but may miss a diagnosis if the relevant mutation is not present in the cells analyzed.
ctDNA only provides mutation information and cannot reveal gene expression, which is crucial for understanding tumor behavior and personalized treatment.
The content of ctDNA in early-stage cancer is usually extremely low, increasing the risk of missed diagnosis.
ctDNA testing cannot directly assess the effects of drugs or natural substances on cancer cells.
What is CTC?
Circulating tumor cells (CTCs) are intact cancer cells that break away from the primary tumor and enter the blood. Analyzing CTCs can provide important information about cancer progression, treatment efficacy, and risk of recurrence.

CTC Detection Method
CTC detection isolates and analyzes these cells using techniques such as flow cytometry, which can obtain more than 99% viable cells and directly test chemotherapy drugs, targeted therapy drugs and natural substances to evaluate their effectiveness for patients and cancer types.

The main differences between ctDNA and CTC
- Real-time monitoring:
ctDNA reflects the past activities of dead cells, while CTC provides real-time tumor dynamic information. - Tumor heterogeneity:
CTC reflects the diversity of tumor cells, including different mutations and transformation subpopulations. - Gene expression analysis:
CTC retains genomic and transcriptomic information and can be comprehensively analyzed, while ctDNA cannot provide this information. - Early detection:
CTC can be detected in the early stages of tumors or even before clinical detection, while ctDNA detection may miss the diagnosis. - Drug sensitivity testing:
CTC can be cultured and tested for drug effects, while ctDNA does not have this function.
Comparison of CTC and ctDNA in cancer detection
CTC | ctDNA | |
Real-time monitoring of tumors | Yes | Limited |
Tumor Heterogeneity | High | Limited |
Gene expression profile of cancer cells | Yes provide insights into the specific biological characteristics of an individual’s tumor, which provide information on personalized treatment | No |
Early stage cancer detection | High | Limited |
Directly testing cancer drugs on cancer cells | Yes | No |
Summarize
Although ctDNA can reveal tumor genetic changes and monitor treatment response, it comes from dead cells and may not fully reflect the current state of the tumor. CTC detection can not only monitor tumors in real time, but also detect cancer early and directly evaluate drug effects, making it a more comprehensive tool in cancer management.
Medical Disclaimer:
The information provided in this article is for educational and reference purposes only and does not constitute medical advice and should not be used as a substitute for professional medical diagnosis, treatment or advice. If you have any questions about your health or medical issues, you should always consult your physician or other qualified medical professional. The content of this article is not intended to recommend any specific test, treatment or medication and should not be construed as such. If you experience symptoms or require medical assistance, please contact a healthcare professional promptly.