Measuring the number of circulating tumor cells (CTCs) or circulating tumor DNA (ctDNA) in the blood can help give prognostic information on recurrence risks after treatment.
CTCs may help identify subsets of at-risk patients that imaging and other traditional surrogates like stage or size of primary may have missed.
As an integrative oncologist, tracking CTC numbers over time helps me see the potential impact of other therapies, lifestyle modifications and biohacking strategies on cancer recurrence.
CTC and circulating tumor DNA testing is not standard in oncology, as large prospective studies have not yet been published to prove their value in helping to guide treatment to improve outcomes. I expect this to become a standard prognostic tool in the next few years.
Would you change your lifestyle if you knew you had silent (occult) cancer cells hiding in your body?
We know that cancer cells often spread early in the course of disease and they can remain silent (occult or hidden) for years.
- Among women with the earliest stage of invasive breast cancer (stage 1), 25% of them already have breast cancer cells that can be found in their bone marrow. (reference)
- Among men with the earliest stages of prostate cancer (pT2, no lymph node involvement, Gleason scores </=6, PSA </=4 ng/mL), over 70% of them have prostate cancer cells that can be found in their bone marrow. Even among the men who are presumed cured after prostatectomy (3 months postoperative PSA <0.4 ng/mL), 57% of them have prostate cancer cells within their bone marrow. (reference)
- A study in patients with early stage lung cancer who had greater than 4 CTCs/mL of blood before radiation treatment (SBRT) had a four times higher risk of developing metastatic disease.
These and many other studies confirm that the silent (occult) presence of these metastatic cells, whether they are in the bone marrow (called, “disseminated tumor cells” or “DTC’s”) or circulating within the blood (called, “circulating tumor cells” or “CTC’s”), is not surprisingly associated with a higher rate of recurrence and death from their cancer in the future.
CTC’s are able to be detected by taking a sample of the patients blood and submitting it for analysis. DTC’s are detected by analyzing a sample of tissue taken from a bone marrow biopsy (a more painful procedure than a blood draw, and thus less desirable.)
Studies have clearly shown that not all patients with measurable CTC’s or DTC’s will go on to develop a detectable metastatic tumor. These cells may be attacked and killed by the body’s immune system, they may self-destruct (apoptosis) or they may remain dominant within the body. However, if the conditions are right they will grow into a metastatic tumor. These conditions can include:
- suppressed immune system
- excessive free radicals (oxidation)
- stimulation by tumor growth factors/hormones
The Future of CTC and ctDNA Testing-Guided Management:
Researchers are currently studying the clinical use of tailoring cancer treatment (i.e. chemotherapy, immune therapy, etc.) based on the response as measured by following the number of CTC’s or DTC’s. This is an exciting area of research, as typically oncologists will give a cancer-killing drug for 1-3 months before assessing the response to treatment using radiographic scans (i.e. PET/CT, CT, MRI, etc.). The use of CTC or DTC analysis enables the oncologist to assess response to treatment after each dose of drug, facilitating a more rapid change to an alternative drug that may be more effective. Use of CTC’s and DTC’s to tailor cancer treatment may be one of the most important advances in the field of oncology.