New Hope in Cancer Detection: Circulating Tumor Cell (CTC) Testing
CTC testing offers new possibilities for early detection, recurrence monitoring, and precision treatment for cancer patients in Hong Kong.
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In Hong Kong, cancer has topped the list of the ten leading causes of death for many consecutive years. Whether it is lung cancer, colorectal cancer, breast cancer, or liver cancer, the battle is long and grueling for both patients and their families. Most patients recall that their diagnosis came only when symptoms were obvious or when the tumor had already grown to a detectable size. This feeling of “finding out too late” is an almost universal source of anxiety among cancer patients.
Traditional cancer screening relies on tumor markers (e.g., CEA, CA-125 blood tests), X-rays, computed tomography (CT), magnetic resonance imaging (MRI), and even positron emission tomography–computed tomography (PET-CT). Yet all these methods share one critical limitation: tumors usually need to reach 0.5–1 cm or larger before they can be detected. By the time a diagnosis is confirmed, patients have often already missed the earliest and most treatable window — the golden period of cancer care.
Faced with this reality, patients in Hong Kong have long yearned for a test that can detect cancer “one step earlier” — a technology capable of picking up the faintest clues while cancer is still in its infancy. The emergence of circulating tumor cell (CTC) testing is turning that wish into reality.
What are circulating tumor cells (CTCs)?
Blind Spots of Conventional Testing
Almost everyone has heard of “tumor markers.” However, many Hong Kong patients discover during routine check-ups that normal marker levels do not guarantee the absence of cancer cells, while elevated levels do not always confirm cancer.
Similarly, although CT and PET-CT scans are far more precise than plain X-rays, they still require the tumor to grow to a visible size. In other words, when imaging finally “sees” a tumor, billions or even tens of billions of cancer cells may already be present in the body. For patients who hope to “detect early and treat early,” this is a harsh truth.
Circulating Tumor Cells (CTCs): Early Warning Signals in the Blood
As early as the 1990s, scientists began exploring whether cancer cells could be captured directly from blood. Even when the primary tumor is still tiny, some cancer cells may shed into the bloodstream and travel to distant sites. These are known as circulating tumor cells (CTCs).
Today, thanks to technological advances, researchers can use specialized antibodies, biochips, and filtration techniques to isolate as few as one cancer cell from just 7–10 mL of blood. For patients, this is like having an “early warning system” for cancer.
The key advantages of CTC testing include:
- Detecting risk before tumors become visible on imaging
- Helping doctors and patients monitor for possible recurrence or metastasis
- Guiding personalized treatment, because the captured cancer cells are viable and can undergo drug-sensitivity analysis
Lessons from Clinical Cases in Hong Kong and Asia
International studies and clinical experience in Asia have repeatedly shown that CTCs can already be detected in stage I colorectal cancer and early-stage breast cancer — a crucial early signal.
Hong Kong patients often hope to “catch the earliest possible changes” during regular health screenings. If CTC testing can identify cancer cells 6–12 months earlier than conventional methods, treatment can start sooner, dramatically improving survival rates and quality of life.
Cancer Cells Are Like Seeds: The Environment Determines Whether They “Sprout”
The easiest analogy for patients is to picture cancer cells as “seeds.” In early cancer, these seeds may already be circulating in the blood, but they do not necessarily take root immediately.
If the body’s internal environment is healthy and the immune system is strong, many seeds will be cleared. However, chronic inflammation caused by:
- High-sugar, high-fat diets and excessive red meat
- Chronic sleep deprivation and lack of exercise
- Prolonged stress and reduced immunity can create fertile “soil,” allowing the seeds to implant and proliferate into tumors. This is why numerous studies emphasize that improving lifestyle habits can significantly lower cancer risk.
From the Patient’s Perspective: Peace of Mind and Real Choices
Many Hong Kong patients, especially those who have just finished surgery or chemotherapy, live in fear of recurrence. Even when scans appear clear, the worry “could cancer still be hiding?” persists. CTC testing offers psychological reassurance.
If CTCs are still detected, the doctor and patient can discuss:
- Whether treatment needs to be intensified
- Whether oral targeted drugs should be considered
- Whether more frequent monitoring is required
Conversely, a negative CTC result brings genuine peace of mind and reduces unnecessary anxiety.
A New Chapter in Precision Medicine: Far Beyond Detection
CTC testing is not simply about “present or absent.” Because the captured cells are live cancer cells, their sensitivity to different drugs can be tested. This means treatment is no longer a uniform standard but truly tailored to each patient’s tumor biology — the essence of precision medicine.
For example, one Hong Kong breast cancer patient who underwent CTC testing discovered that her cancer cells were sensitive to certain chemotherapy agents but resistant to others. Her oncologist could then avoid ineffective drugs, reduce side effects, and improve efficacy.
Conclusion: CTCs — Another Source of Strength for Cancer Patients in Hong Kong
The greatest challenge of cancer is its silent progression; by the time it is discovered, it is often already advanced. For patients in Hong Kong, CTC testing represents not only scientific progress but also psychological support — a way to gain earlier, clearer control over one’s health while fighting cancer.
As the technology becomes more accessible and clinically validated, CTC testing is expected to become a standard part of cancer management. It offers the promise of earlier detection and truly personalized treatment pathways.
Cancer is frightening, but knowledge and technology give us less helplessness and more choices. For every cancer patient in Hong Kong, this is hope.
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References
- Alix-Panabières, C., & Pantel, K. (2014). Challenges in circulating tumour cell research. Nature Reviews Cancer, 14(9), 623–631. https://doi.org/10.1038/nrc3820
- Cristofanilli, M., Budd, G. T., Ellis, M. J., Stopeck, A., Matera, J., Miller, M. C., Reuben, J. M., Doyle, G. V., Allard, W. J., Terstappen, L. W., & Hayes, D. F. (2004). Circulating tumor cells, disease progression, and survival in metastatic breast cancer. New England Journal of Medicine, 351(8), 781–791. https://doi.org/10.1056/NEJMoa040766
- 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. https://doi.org/10.1038/s41571-019-0187-3
- Park, J. Y., & Hwang, S. Y. (2021). Clinical application of circulating tumor cells for the management of solid tumors. Cancer Research and Treatment, 53(1), 1–15. https://doi.org/10.4143/crt.2020.659
- Wang, J., Chang, S., Li, G., & Sun, Y. (2017). Application of liquid biopsy in precision medicine: Opportunities and challenges. Frontiers of Medicine, 11(4), 405–418. https://doi.org/10.1007/s11684-017-0545-x