Circulating Tumor Cells (CTCs): New Hope for Cancer Patients in Hong Kong
CTC testing provides cancer patients with a new approach for early metastasis detection, treatment response monitoring, and recurrence risk assessment.
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Cancer is one of the leading causes of death in Hong Kong. According to data from the Hong Kong Cancer Registry, cancer claims more than 14,000 lives every year, with the vast majority of these deaths caused by metastasis. In recent years, with advances in medical technology, the detection of circulating tumor cells (CTCs) has gained increasing attention and is regarded as an important new tool for cancer diagnosis, monitoring, and prognosis. This article explores the significance and clinical value of CTC testing from the perspective of patients in Hong Kong.
What Are Circulating Tumor Cells (CTCs)?
At different stages of cancer development, tumor cells may detach from the primary tumor and enter the bloodstream. These cancer cells circulating in the blood are called circulating tumor cells (CTCs). They are regarded as the “seeds” of metastasis, capable of traveling through the bloodstream to distant organs such as the liver, lungs, bones, or brain, eventually forming distant metastases (Wu, 2023). Clinically, metastasis is the primary reason most solid tumors remain incurable.
Liquid Biopsy: A Minimally Invasive Testing Approach
Traditionally, assessing tumor status required invasive tissue biopsies, which carry risks and discomfort for patients. In contrast, liquid biopsy involves drawing a blood sample to directly detect CTCs and other tumor-related molecular signals (Esen Medical, 2021). This method is minimally invasive and can be repeated at multiple time points, making it particularly valuable for cancer patients requiring long-term monitoring.
Clinical Applications of CTCs
- Prognosis and Survival Correlation Numerous studies have shown that CTC count in the blood is negatively correlated with overall survival in many solid tumors (e.g., breast, colorectal, lung, and prostate cancer). In other words, higher CTC numbers are generally associated with poorer prognosis (JWDx, 2023).
- Monitoring Treatment Response Changes in CTC count can reflect tumor response to therapy. For example, a decrease in CTCs after chemotherapy, targeted therapy, or immunotherapy often indicates treatment efficacy, whereas an increase may suggest poor response and the need to adjust the treatment plan (Wu, 2023).
- Early Detection of Recurrence After tumor resection or completion of treatment, CTC testing can help detect signs of recurrence at an early stage. Because it only requires repeated blood draws, patients are spared the risks of additional invasive tissue biopsies (Esen Medical, 2021).
The Relationship Between CTCs and Cancer Metastasis
To enter the bloodstream, cancer cells must undergo epithelial-mesenchymal transition (EMT). During EMT, cancer cells lose epithelial characteristics and gain enhanced invasiveness and motility, enabling them to breach the basement membrane and enter circulation (Wu, 2023). These CTCs represent a critical prelude to distant metastasis. Studies have confirmed that the presence of CTCs is associated with poor prognosis in patients with breast, esophageal, pancreatic, and colorectal cancers (Esen Medical, 2021).
Technical Challenges and Future Directions
Despite its great potential, CTC detection still faces challenges. In each milliliter of blood, there are approximately 10 billion red blood cells and 1 million white blood cells, yet only 1–10 CTCs may be present — extremely rare (JWDx, 2023). Effectively enriching and accurately detecting these cells remains a major scientific hurdle. With ongoing technological improvements in detection technology, the future may allow CTCs to be cultured into cell lines for molecular profiling of a patient’s tumor, thereby guiding truly personalized treatment.
Significance for Patients in Hong Kong
Cancer patients in Hong Kong are often deeply concerned about metastasis and recurrence. CTC testing, through a simple blood draw, provides patients and clinicians with valuable real-time information: whether treatment is working, whether the regimen needs adjustment, and whether there is risk of recurrence. For patients, this represents a gentler yet continuous monitoring approach, bringing greater transparency and reassurance throughout their cancer journey.
Conclusion
CTC testing represents a major advance in oncology. Although it has not yet fully replaced traditional diagnostic methods, it has become an indispensable complementary tool in clinical practice. For cancer patients in Hong Kong, CTCs are not just a new technology — they offer genuine hope, enabling earlier detection of metastasis risk and giving patients greater control and agency throughout treatment.
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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/