How to Choose the Best Circulating Tumor Cell (CTC) Test？
CTC testing offers a new approach to early detection, risk assessment, and personalized treatment for cancer patients in Hong Kong.
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Cancer remains Hong Kong’s number one killer, claiming more than 14,000 lives every year, the majority due to metastasis (Hong Kong Cancer Registry, 2023). With advances in medical technology, circulating tumor cell (CTC) testing has emerged as a powerful new tool for cancer diagnosis and treatment monitoring. However, numerous CTC testing technologies are now available on the market. For patients, choosing the most suitable and reliable test is a practical and critical decision.
Practical Considerations for Patients in Hong Kong
What Are Circulating Tumor Cells (CTCs)?
CTCs are cancer cells that shed from the primary tumor (or metastases) and enter the bloodstream, either as single cells or clusters. They are regarded as the “seeds” of metastasis and can travel via blood to the liver, lungs, bones, or brain, leading to distant metastases (Wu, 2023). Detecting and analyzing CTCs not only helps clinicians understand disease progression but also provides vital information for personalized treatment (Esen Medical, 2021).
Five Key Factors When Choosing a CTC Test
1.Sensitivity and Specificity
CTCs are extremely rare — typically only a few cells per milliliter of blood, surrounded by billions of blood cells (JWDx, 2023).
- Magnetic bead-based methods: sensitivity only ~50–60%, rely on a single marker, easily miss heterogeneous CTCs → not ideal for clinical use (Esen Medical, 2021).
- PCR-based methods: detect genetic markers but cells are non-viable, limiting subsequent drug testing (Wu, 2023).
- Microscopic enumeration: mainly provides count, limited sensitivity/specificity.
- Flow cytometry: high sensitivity and specificity, can detect diverse CTC subpopulations simultaneously, and preserves cell viability >99% — widely regarded as the gold standard for clinical and research applications (RGCC, 2023). For Hong Kong patients, detecting diverse and highly aggressive CTC subpopulations is far more valuable than a simple “present/absent” result.
2.Real Clinical Samples vs. Spiked Samples
- Some tests claim >90% sensitivity, but the data come from artificially “spiked” samples rather than real patient blood (JWDx, 2023). Performance in spiked samples often overestimates real-world efficacy. Patients should prioritize technologies validated on actual clinical specimens.
3. Viability of Isolated CTCs
Whether CTCs remain alive after isolation determines whether downstream molecular analysis or drug-sensitivity testing is possible:
- Flow cytometry: viability >99%, suitable for personalized drug testing (RGCC, 2023).
- PCR / microscopic methods: cells are dead, no downstream functional assays possible (Esen Medical, 2021). If a patient wants drug-sensitivity results from their own tumor cells, preserving high viability is essential.
4. Balancing Cost and Clinical Value
Many Hong Kong patients worry about cost, but low-price tests often have serious limitations:
- Rely on a single marker (e.g., EpCAM only) → miss high-risk CTCs that have undergone epithelial-mesenchymal transition (EMT) (Wu, 2023).
- Isolated cells are usually non-viable → no drug testing possible.
- Higher risk of false-negative results → delayed treatment. Accuracy and comprehensiveness should take priority over cost alone. A single false-negative can mean missing the critical treatment window.
5. Laboratory Accreditation and Compliance
Choosing an internationally accredited laboratory ensures quality and reliability:
- CLIA certification (U.S. clinical laboratory standards)
- ISO certification (international quality management)
- CAP accreditation (College of American Pathologists) Hong Kong patients should actively verify the laboratory’s credentials.
Why CTC Heterogeneity Cannot Be Ignored
CTCs are not uniform. Different subpopulations carry distinct genetic and phenotypic markers. Tests relying on a single marker (e.g., EpCAM) will miss large numbers of EpCAM-negative CTCs — which are often the most invasive and metastatic (Esen Medical, 2021). Consequences for patients:
- False-negative results
- Delayed treatment
- Underestimation of metastasis risk
- Limited treatment personalization
Therefore, the ability to detect heterogeneous CTCs is a crucial selection criterion.
Advantages of RGCC CTC Testing
RGCC uses advanced flow cytometry with both positive and negative selection, capturing CTCs regardless of conventional marker expression. Key advantages:
- Sensitivity 86.2% and specificity 83.9% (validated on real patient samples) (RGCC, 2023)
- Cell viability >99%, enabling subsequent drug-sensitivity testing
- Tests response to 50+ chemotherapies, 60+ targeted therapies, and 50+ natural compounds
- Multiple international accreditations (CLIA, ISO, CAP)
For Hong Kong patients, this translates into earlier risk detection and truly personalized treatment options.
Conclusion
CTC testing offers new hope for cancer patients in Hong Kong. It goes far beyond simply detecting “cancer cells or not” — it reveals tumor heterogeneity, treatment response, and metastasis risk. Choosing the right technology means earlier accurate diagnosis, avoidance of misleading results, and a clearer path to personalized therapy. For patients, investing in a reliable CTC test is investing in better survival chances and quality of life.
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References
- Esen Medical. (2021). Circulating Tumor Cells and Cancer. https://www.esenmedical.com/article/circulating-tumor-cellsand-cancer
- JWDx. (2023). What is CTC testing? https://www.jwdx.com.tw/ctc檢測是什麼/
- Wu, H. (2023). Clinical significance and applications of circulating tumor cell testing. https://www.drhenrywu.com/ctc/
- RGCC. (2023). CTC Testing and Personalized Cancer Care. RGCC International.