Using circulating tumour cells to monitor residual disease and to choose the next line when colorectal cancer has already been through standard protocols.
Hong Kong context Colorectal cancer was the third most common cancer in Hong Kong in 2023, with 5,467 new cases (3,169 in men, 2,298 in women). It remains one of the leading causes of cancer death locally, and many patients present after the window for simple polypectomy has closed. |
Why this cancer is hard to manage with a single protocol
Stage II and III colorectal cancer is often treated with a relatively standard adjuvant backbone. Metastatic disease then moves through fluoropyrimidines, oxaliplatin, irinotecan, anti-VEGF or anti-EGFR antibodies, and later trifluridine/tipiracil or regorafenib. RAS, BRAF and MSI / MMR status narrow the list — they do not tell you which remaining drug will actually kill this patient’s circulating cells.
CEA is useful when it tracks with disease, and useless when it does not. CT and MRI show bulk. They do not show whether a clone that survived FOLFOX is still circulating after the scan has improved.
RGCC has published work on enumerating and immunophenotyping CTCs in colorectal cancer, and preliminary clinical work on adjusting second-line therapy in metastatic colorectal cancer using CTC-guided information. That is the clinical niche this article is written for: not first diagnosis of a polyp, but living with the disease after the first protocol.
What circulating tumor cells add
Colorectal CTCs can be isolated from peripheral blood and characterised. Oncotrail RGCC includes a colon / GI panel. The test reports CTC concentration and markers that speak to origin and activity, so it can be used as a baseline at the start of a line of treatment and again at defined intervals.
Because colorectal cancer sheds into portal and systemic circulation, blood-based monitoring is biologically plausible even when the liver lesion looks stable. A rising CTC count with aggressive stemness markers is a reason to restage earlier than the next booked scan.
The RGCC pathway for this cancer
A typical sequence is screening or baseline first, then a comprehensive profile when treatment choices matter, then serial follow-up. The exact panel is chosen by the accredited practitioner.
Clinical question | RGCC test to consider |
Average-risk or high-risk adult, no diagnosis | Onco-D-clare as an adjunct to FIT / colonoscopy — not a replacement for colonoscopy |
Confirmed colon or rectal cancer; baseline and serial monitoring | Oncotrail RGCC (colon / GI panel) |
Choosing first systemic line, or switching after progression | Onconomics Plus — sensitivity to chemo and targeted agents plus natural compounds and resistance genes |
Interval burden check only | Oncocount |
Unknown primary in the abdomen, or need chromosomal overview | ArrayCGH RGCC, with CTC phenotype from Oncotrace |
Metastatic pattern / spread risk | Metastat |
What the report can change in practice
Used well, the report answers three questions the MDT already asks. Is there measurable circulating disease after surgery or during chemo? Which of the remaining cytotoxic and targeted options look active against the cells that are circulating now? Are resistance mechanisms (efflux pumps, relevant pathway genes) already up?
For patients exploring integrative care — common in Hong Kong and Singapore after the first two lines — the natural-substance panel stops the conversation being anecdotal. The practitioner can see which extracts showed cytotoxic or immunomodulatory activity against that person’s CTCs in the assay, and which did not.
None of this removes the need for RAS / BRAF / MSI testing on tissue or ctDNA. CTC functional testing and genomic testing answer different questions. Use both.
Who this article is for
• Patients with stage II–IV colorectal cancer before or during systemic therapy.
• People whose CEA and scans disagree.
• Metastatic disease facing a second or later line.
• Patients in surveillance after resection who want an additional blood-based tool.
• Adults over 50, or younger adults with family history, discussing screening options alongside FIT and colonoscopy.
Next step
If you already have a colonoscopy and pathology report, an RGCC-accredited practitioner can tell you whether Oncotrail or Onconomics Plus is the right first blood test. Bring RAS / BRAF / MSI results if you have them — they sit beside, not instead of, the CTC profile.
Disclaimer. This article is educational and is intended for patients, families, and referring practitioners. RGCC tests are laboratory investigations that support clinical decision-making. They do not replace imaging, tissue diagnosis, or a treating oncologist’s judgement. Results must be interpreted by an RGCC-accredited practitioner in the context of the full medical history. RGCC circulating tumor cell (CTC) assays are not designed to detect primary cancers of the brain or central nervous system. Always discuss findings with your own doctor before changing any treatment.