Circulating Tumor Cells (CTC)

Conclusion First If you or a loved one is facing colorectal cancer, CTC testing is not a magic bullet, but it has real, actionable clinical value in four key areas:
• Risk stratification
• Treatment response monitoring
• Early warning of recurrence
• Supporting immunotherapy decisions
It works best after diagnosis, around surgery, and during systemic therapy (chemo/targeted/immunotherapy). It does not replace colonoscopy, imaging, or CEA, but it often gives an earlier, more dynamic signal. In oncology, that earlier signal can be the difference between months or years of survival. (SEER; American Cancer Society)
Colorectal cancer 5-year relative survival is heavily stage-dependent: overall ~65%, but drops to ~14% once distant metastases appear (stage IV). From a patient’s view, the message is brutally simple: catch it early and keep watching aggressively. CTCs are one of the best tools we have for the “keep watching” part.

Cancer treatment has changed beyond recognition in the past few decades. Chemotherapy was once the only weapon, but it attacked healthy cells as fiercely as cancer cells. Targeted therapy improved precision, yet only a minority of patients have the “right” mutations.

Breast cancer has been the number-one cancer among women in Hong Kong for many years, with thousands of new cases diagnosed annually. Whether undergoing surgery, chemotherapy, targeted therapy, or hormone therapy, every patient shares the same burning questions:
“Is my treatment actually working?”
“Will my cancer come back or spread?”
Traditional monitoring tools — imaging scans (CT, PET-CT, bone scans) and serum markers (CEA, CA15-3) — are familiar to every patient, but in the era of precision medicine they often feel too slow, too vague, or simply too late.

Clinical Evidence and Real-World Insights for Patients
In an era of rapid medical progress, the way we detect and treat cancer is evolving dramatically. For liver cancer (hepatocellular carcinoma, HCC) patients, early detection and accurate disease monitoring can literally be the difference between life and death. Traditional tools such as ultrasound, AFP levels, and contrast-enhanced imaging, while widely used, have clear limitations. This is why scientists have been racing to develop the next generation of blood-based tests — and circulating tumor cells (CTCs), a cornerstone of liquid biopsy, are quietly revolutionizing how we understand and manage liver cancer.

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.

The core reason cancer is so difficult to completely cure lies in metastasis. Even if the primary tumor is surgically removed or shrunk, residual cancer cells that disseminate outward and take root in distant organs can trigger new tumors, becoming the leading cause of death. From the patient’s perspective, we’ll use straightforward analogies and scientific mechanisms here to explain why this is so challenging, as well as the possibilities and limitations of detecting circulating tumor cells (CTCs) in the blood.

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.

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.