The Key to Personalized Cancer Medicine
From traditional to individualized approaches, circulating tumor cell (CTC) testing and liquid biopsy help Hong Kong cancer patients obtain the most suitable treatment strategies.
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Introduction — From “One-Size-Fits-All” to “Tailored to the Individual”
Cancer incidence continues to rise in Hong Kong. According to the Hong Kong Cancer Registry, there were more than 34,000 new cancer cases and nearly 15,000 cancer-related deaths in 2020 (Hong Kong Cancer Registry, 2022).
In the past, cancer treatment followed standardised protocols — patients with the same stage often received nearly identical treatments. However, clinical experience has shown huge variability in treatment response between individuals.
The rise of personalized oncology aims to break away from this “one-size-fits-all” approach. In this transformation, Circulating Tumor Cell (CTC) testing and liquid biopsy have emerged as key technologies.
The Core Logic of Personalized Medicine
The essence of personalized oncology is to tailor treatment based on:
- Tumour characteristics
- Genetic mutations
- Molecular biomarkers
- Individual patient factors
(Dienstmann et al., 2017).
It rests on three pillars:
- Genetic testing and molecular diagnostics – to identify driver mutations
- Circulating Tumor Cell (CTC) analysis – for dynamic monitoring
- Clinical and personal factors – age, comorbidities, lifestyle, frailty status
Scientific Foundation of Circulating Tumor Cells (CTCs)
1. Definition
CTCs are tumour cells shed from primary or metastatic lesions into the bloodstream (Alix-Panabières & Pantel, 2014). Though extremely rare, they are the key precursors of metastasis.
2. Biological Characteristics
- Single CTCs：Short lifespan (25–30 minutes)
- CTC clusters：Bind to platelets and neutrophils → stronger immune evasion and metastatic potential (Szczerba et al., 2019)
- Molecular heterogeneity：CTCs may show HER2 amplification or PIK3CA mutations different from the original tumour(Micalizzi et al., 2017)
3. Timing and Chronobiology
Recent evidence shows CTCs are shed more abundantly at night, suggesting metastasis follows a circadian rhythm (Diamantopoulou et al., 2022).
CTC Testing Technology & Liquid Biopsy
1. Limitations of Traditional Diagnostics
- Tissue biopsy is invasive and cannot be done frequently
- Imaging cannot detect minimal residual disease
- Serum tumor markers lack specificity
2. CTC Detection Technologies
| Method | Principle | Example |
|---|---|---|
| Antigen-dependent | Captures EpCAM-expressing cells | CellSearch (FDA-cleared) (Allard et al., 2004) |
| Antigen-independent | Separates by size, density, or electrical properties | Microfluidic platforms such as Parsortix or CTC-iChip (Ozkumur et al., 2013) |
| Hybrid approaches | Combines biophysical + immunological signals | Higher sensitivity/specificity |
Antigen-dependent
Principle: Captures EpCAM-expressing cells
Example: CellSearch (FDA-cleared) (Allard et al., 2004)
Antigen-independent
Principle: Separates by size, density, or electrical properties
Example: Microfluidic platforms such as Parsortix or CTC-iChip (Ozkumur et al., 2013)
Hybrid approaches
Principle: Combines biophysical + immunological signals
Example: Higher sensitivity/specificity
3. Positioning of Liquid Biopsy
Liquid biopsy includes CTCs, ctDNA, and exosomes.
Among them, CTCs are the only source of viable intact tumour cells — allowing downstream functional testing (genomics, transcriptomics, and drug sensitivity assays).
Clinical Value of CTCs in Personalized Oncology
1. Prognostic Assessment
In metastatic breast cancer, baseline CTC ≥ 5 per 7.5mL blood predicts significantly worse survival (Cristofanilli et al., 2004).
2. Monitoring Treatment Response
CTC trends can reveal therapeutic efficacy earlier than imaging (Paoletti et al., 2015).
3. Resistance Mechanism Analysis
CTC sequencing can detect resistance mutations (e.g., EGFR T790M) guiding escalation to newer targeted agents (Mok et al., 2009).
4. Minimal Residual Disease (MRD)
CTCs can detect relapse 7–9 weeks before clinical or radiological evidence (Alix-Panabières & Pantel, 2014).
Challenges from the Hong Kong Patient Perspective
| Issue | Description |
|---|---|
| Cost | CTC & liquid biopsy are self-financed; fees range from thousands to tens of thousands HKD. |
| Public–private gap | Faster adoption in private sector; limited availability in HA hospitals. |
| Information | Patients lack time to understand results during short consultations; online resources are fragmented. |
| Psychological burden | Some fear “knowing more means more worry”; counselling is often needed. |
Cost
CTC & liquid biopsy are self-financed; fees range from thousands to tens of thousands HKD.
Public–private gap
Faster adoption in private sector; limited availability in HA hospitals.
Information
Patients lack time to understand results during short consultations; online resources are fragmented.
Psychological burden
Some fear “knowing more means more worry”; counselling is often needed.
Future Outlook
- Clinical integration — combine CTC with ctDNA and exosomal biomarkers
- Technological breakthroughs — improve sensitivity and standardisation
- Policy development — potential inclusion in HA studies or subsidy frameworks
- Patient education — help patients understand and participate in care decisions
Conclusion
The essence of personalized oncology is ensuring “the most effective, safest, and most appropriate treatment for each individual patient.”
CTC analysis and liquid biopsy are giving Hong Kong patients a new pathway toward that goal.
They do not replace traditional care, but enhance and upgrade it — helping the healthcare system evolve from “standard protocol” to “patient-specific strategy,” and helping patients shift from passive recipients to informed participants in their own cancer treatment journey.
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References
- Alix-Panabières, C., & Pantel, K. (2014). Clinical applications of circulating tumor cells and circulating tumor DNA as liquid biopsy. Cancer Discovery, 4(6), 650–661.
- Allard, W. J., Matera, J., Miller, M. C., Repollet, M., Connelly, M. C., Rao, C., … & Terstappen, L. W. (2004). Tumor cells circulate in the peripheral blood of all major carcinomas but not in healthy subjects or patients with nonmalignant diseases. Clinical Cancer Research, 10(20), 6897-6904.
- Cristofanilli, M., Budd, G. T., Ellis, M. J., Stopeck, A., Matera, J., Miller, M. C., … & Hayes, D. F. (2004). Circulating tumor cells, disease progression, and survival in metastatic breast cancer. New England Journal of Medicine, 351(8), 781-791.
- Diamantopoulou, Z., Castro-Giner, F., Schwab, F. D., & Aceto, N. (2022). The metastatic spread of breast cancer accelerates during sleep. Nature, 607(7917), 156-162.
- Dienstmann, R., Rodon, J., Barretina, J., & Tabernero, J. (2017). Genomic medicine frontier in human solid tumors: Prospects and challenges. Journal of Clinical Oncology, 35(9), 929–946.
- Micalizzi, D. S., Maheswaran, S., & Haber, D. A. (2017). A conduit to metastasis: circulating tumor cell biology. Genes & Development, 31(18), 1827–1840.
- Mok, T. S., Wu, Y. L., Thongprasert, S., Yang, C. H., Chu, D. T., Saijo, N., … & Fukuoka, M. (2009). Gefitinib or carboplatin–paclitaxel in pulmonary adenocarcinoma. New England Journal of Medicine, 361(10), 947-957.
- Ozkumur, E., Shah, A. M., Ciciliano, J. C., Emmink, B. L., Miyamoto, D. T., Brachtel, E., … & Toner, M. (2013). Inertial focusing for tumor antigen–dependent and –independent sorting of rare circulating tumor cells. Science Translational Medicine, 5(179), 179ra47.
- Paoletti, C., Muñiz, M. C., Thomas, D. G., Griffith, K. A., Kidwell, K. M., Tokudome, N., … & Hayes, D. F. (2015). Development of circulating tumor cell–endocrine therapy index in patients with hormone receptor–positive breast cancer. Clinical Cancer Research, 21(11), 2487–2498.
- Pantel, K., & Alix-Panabières, C. (2019). Liquid biopsy and minimal residual disease — latest advances and implications for cure. Nature Reviews Clinical Oncology, 16(7), 409–424.
- Wong, C. K. H., Lam, C. L. K., Wan, Y. F., Fong, D. Y. T., & Lam, W. W. T. (2018). Health-related quality of life in Chinese patients with cancer: Validation of the European Organization for Research and Treatment of Cancer QLQ-C30. Supportive Care in Cancer, 26(8), 2611–2620.