FAQs about the maintrac method

maintrac is a diagnostic laboratory method for quantitative detection of epithelial cells in blood that are likely to originate from a tumour.

What are circulating epithelial tumour cells (CETCs)?

Solid tumors can seed tumour cells into peripheral blood. It is now clear that cells are shed from tumours well before the formation of metastases. They can be shed from the tumour at all stages of disease and may remain in the patient’s circulation for lengthy periods. Epithelial antigens called EpCAMs (epithelial cell adhesion molecules) are expressed on cells of epithelial origin, such from solid tumours. These antigens are not usually found on blood cells. This antigen can be stained with a green fluorescent antibody. The blood cells are also stained with an anti-CD45 antibody. The live EpCAM-positive cells are detected and enumerated microscopically. This is possible with an additional dead/live staining dye called propidium iodide. All cells that the dye is able to enter due to having a permeable membrane are excluded. EpCAM stains all epithelial cells. Normal epithelial cells are also detected if these are present. If the patient has a tumour, it is most likely that the epithelial cells are tumour cells.

M El Sherif et al. Behaviour of Circulating Epithelial Tumor Cells (CETCs) and FISH (Fluorescence In Situ Hybridization) of Epidermal Growth Factor Receptor (EGFR)-gene amplification in lung cancer patients during the course of therapy. Advances in Lung Cancer
Vol.2  No.1(2013)   https://static1.squarespace.com/static/5316afe0e4b0fe5194112977/t/5435d688e4b08989f8c7e969/1412814472595/2014+CETC+EGFR+in+lung+cancer.pdf

Monitoring the behaviour (increase or decrease) of CETCs enables the timely detection of imminent recurrence and evaluation of treatment response for many cancers.

What is the difference between tumour cells and epithelial tumour cells (CETCs)?

Tumour cells refer to cells of all tumours, even in leukemias and lymphomas. Epithelial tumour cells refer only to cells from epithelial tumours and carcinomas.

What is the significance of tracking the development of the cell count?

Circulating tumour cells can settle in foreign tissues and grow into metastases. These cells can survive in the body for very long times. The number and growth pattern of circulating tumour cells are key for the course of the patient’s disease.

How is the cell kill effectiveness of different agents determined?

Cell kill effectiveness is determined by exposing all white cells from the cell pellet of 100 μl of blood to different concentrations of the respective agent in medium, where the concentration calculated to be present in the blood of patients under treatment is set as one, and a tenfold lower and a tenfold higher concentration is tested in comparison to the control suspendsion containing the cells without addition of the agent. Cells are cultured under these conditions for up to nine hours and the cytotoxic effect measured at three, six and nine hours. Cells can be characterized as follows: 1) Live blood cells appearing only in transmitted light with no fluorescence staining; 2) Dead blood cells where the membrane has become permeable showing propidium iodide entering the cell, staining the nucleus red fluorescent; 3) Live epithelial (presumably tumor) cells staining with green fluorescence, preferentially as a cap, due to reactivity with FITC-conjugated anti-EpCAM; 4) Dead CETC with simultaneous green and red fluores- cent staining, resulting either in a clear green cap with a red nucleus, or later during nucleic and cell disintegration with an orange combination stain. The numbers of live and dead CETC is determined at each point in time without and with the indicated concentrations of the therapeutic agent and the percentage increase in dead cells over the control is calculated. Quantitative analysis of the samples at different times after incubation with the respective drugs is performed using the image analysis system of the ScanR (Olympus Hamburg, Germany), allowing repeated scanning of the same area. A typical example, showing typical live and dead cells, is shown in Figure 1.

Copyright © 2013 SciRes. JCT Chemosensitivity Testing of Circulating Epithelial Tumor Cells (CETC) in Vitro: Correlation to in Vivo Sensitivity and Clinical Outcome 599

Can maintrac identify the type of cancer and its degree of aggressiveness?

Properties of the circulating tumour cells may indicate the origin of these cells and be a prerequisite for an optimal therapeutic approach. If, however, the cell number increases, this is very likely to be a sign of tumour activity.

Can maintrac prevent metastases?

maintrac is a diagnostic method. It may help early detection of a tendency to metastasise – much earlier than imaging techniques.

Can tumour cells change?

Yes, the response pattern of tumour cells can change even during therapy by various mechanisms that are largely unknown. It is therefore very important to test the tumour cells repeatedly for their properties (genes, receptors) during the course of disease.

Are there threshold values for the cell count?

Every patient is unique, every tumour is distinct. In this respect, there are no generally accepted critical values. In order to determine an increase or decrease in cell count, at least two tests are necessary.

Are there any studies published concerning the maintrac approach?

The significance of maintrac is well documented in studies and published in high-impact journals. The current list of studies can be found here.

Can the course of disease be monitored by maintrac?

Yes, by enumerating the tumour cells at specific intervals, the tumour activity throughout the entire course of disease can be monitored. Since the circulating tumour cells can be inactive for a long time, it is important to follow the cell numbers. If the cell count changes, the current therapy can be promptly adjusted.

Is the chemosensitivity test in vitro comparable to the effectiveness in the patient?

The chemosensitivity test is an indication of the effectiveness of the tested medication. The final success of therapy depends on the concentration achieved in the blood, tumour and metastases.

Does an increase in the number of CETCs correlate with metastases?

An increase in the number of CETCs in the blood may indicate growth of the tumour or metastases, and has been shown to correlate highly significantly with progression.

What are the benefits for patients using maintrac?

In therapy, maintrac enables the practitioner to see how well a therapy is progressing. It is therefore a way to monitor any specific therapy at any stage. The course of disease can be monitored.

Are there any disadvantages for patients using maintrac?

Some patients are afraid when cells are found, when the cells do not respond to therapy and the number of cells increases, as this may be a sign of recurrence. This does however allow prompt adjustment of therapy. Whether the patients want advance information of this kind is for them to discuss with their therapists.

What are the psycho-oncological impacts of maintrac on patients?

A disease like cancer is not easy to bear for patients and their families. Uncertainty as to whether the cancer is now defeated and the fear that it could return are permanent companions. Many patients are grateful for the knowledge that their cell count gives them, enabling them to tolerate the situation better.

Which types of tumours can be diagnosed with maintrac?

The possible application covers solid epithelial tumours (almost all tumours). The laboratory will be glad to assist and advise you in the event of other types of tumour.

Is maintrac just another tumour marker?

Circulating tumour cells are in most cases cells from the tumour itself, and not proteins released by the cells, so whereas tumour markers are secondary, the CETC cell count and the information it provides on tumour activity is more direct.

Is there anything I should be aware of when monitoring the volume of circulating tumour cells?

It is known that tumour cells can downregulate their antigen expression, including the epithelial surface antigen (EpCAM), during increasingly aggressive growth or the so-called epithelial-mesenchymal transition (EMT). This would imply that they may become less detectable or even undetectable for our approach that uses an antibody against EpCAM to detect cancerous cells in blood. In this case we not infrequently observe – after an increase in cell numbers – a sudden decrease to below our detection limit. Under these circumstances we would recommend turning to imaging, and you may wish to consider Stemtrac, which is used to identify cancer stem cells. We strongly suggest patients remain under the care of their oncologists at all times.