Tiny 'cancer trap' could stop cancer spread

Behind the Headlines

Wednesday September 9 2015

Current technology is unable to detect when cancer starts spreading

The trap could pull in circulating cancer cells

"A small sponge-like implant that can mop up cancer cells as they move through the body has been developed," BBC News reports. The implant has only been used in mice, but it could be used in humans to detect and warn about spreading cancer cells. 

The problem is cancer spread from one part of the body to another (metastasis) usually only becomes apparent after it has happened, and when it is often too late to do much about it.

In this latest study, researchers injected mice with breast cancer cells and then put a tiny biological implant or "scaffold" into their abdomen to see if it could catch the cells before they spread to other organs.

The results were promising. Subsequent tests confirmed the scaffold became infiltrated with cancer cells soon after the cancer had developed, and also reduced the spread of cancer to other organs, such as the lungs and liver.

This could have two potential uses. It could provide an "early warning system", alerting clinicians the cancer is beginning to spread, and it could also possibly slow the spread.

However, many questions remain, including whether it would work the same way in humans and for what cancers, how it would be used and, most importantly, if it would be safe.

The new technology has not yet been tested on people.

Where did the story come from?

The study was carried out by researchers from the University of Minnesota and other institutions in the US, and was funded by the National Institutes of Health and the Northwestern H Foundation Cancer Research Award.

It was published in the peer-reviewed scientific journal, Nature Communications.

BBC News gives reliable coverage of the study, making it clear the tests have so far been carried out in mice, and we do not know if the technology is similarly safe and effective in humans.

According to the BBC, the study lead confirmed they were soon planning the first clinical trials in people. 

What kind of research was this?

This laboratory and animal study investigated the potential use of an implant to capture cancer cells spreading through the body to cause metastases – cancer in body sites distant from the original.

Metastases are generally associated with poor prognosis. The researchers consider that if it was possible to identify circulating cancer cells before they have taken hold in other organs, and employ strategies to stop them, this could halt disease progression. So far, several technologies have been investigated to capture and count the number of circulating cancer cells in blood samples.

However, as the researchers say, some cancer cells can be shed into the circulation early on in the course of a cancer, and remain in the circulation for long periods of time before colonising a distant site. Therefore, they aimed to develop a method that would detect and capture these cells.

The study was conducted in mice, and though animal studies can inform how treatments or technologies may work in humans, this is very early-stage research. 

What did the research involve?

This study involved an implant or "scaffold" that could capture metastatic cancer cells, combined with an imaging system to detect them.

The researchers injected cancer cells into the breast tissue of female mice. The cancer cells they chose to inject were a variant known to be highly metastatic. One week after injecting the cancer, the scaffold was implanted into the abdominal fat or beneath the skin.

The scaffold was made of a porous biological material called poly(lactide-co-glycolide) or PLG, which has been approved by the Food and Drug Administration for a number of uses.

When this scaffold is implanted, it triggers an immune response and is colonised by various immune cells. The theory is that these immune cells then "recruit" and capture cancer cells in the scaffold.

Optical imaging (using a system called inverse spectroscopic optical coherence tomography, or ISOCT) was used to detect the arrival of the cancer cells at the implant.

About one month later, the implant and mouse organs were removed and examined in the laboratory. 

What were the basic results?

Both the optical imaging and subsequent examination of the implant/scaffold in the laboratory demonstrated it had captured metastatic cancer cells.

Laboratory examination showed cancer cells were not present elsewhere in the abdominal fat tissue, where the implant had not been placed. Monitoring the initial cancer site also showed implanting the scaffold did not influence growth of the primary tumour in the mammary glands.

Examination of other organs showed the implant reduced the tumour burden of other organs, such as the liver and lung. For example, in the lung of mice who received the implant, the ratio was 1 cancerous cell to 5,400 healthy lung cells. Comparatively, in mice who did not receive the implant, the ratio was 1 to 645. Therefore, the implant reduced the metastatic tumour burden by about 88%.

Other tests showed the implants were recruiting the cancer cells at a much earlier stage than when they arrived in the distant organs. Two weeks after injecting the initial cancer cells, most implants contained cancer cells, compared with minimal tumour burden in other organs until one month.

Further study also confirmed, as expected, immune cells were playing a role in recruiting the cancer cells to the implant.  

How did the researchers interpret the results?

The researchers concluded that, "This study demonstrates a platform technology for the capture and detection of cancer cells early in the metastatic process".

They go on to say that, "For patients at risk of recurrence, scaffold implantation following completion of primary therapy has the potential to identify metastatic disease at the earliest stage, enabling initiation of therapy while the disease burden is low". 

Conclusion

This animal study offers early promise of a new technology that may be able to halt metastatic cancer spread to other sites in the body, which is associated with notoriously poor prognosis.

The study suggested the implant could capture cancer cells shed from the tumour, even in its earliest stages of development, and reduce the eventual spread to other organs.

However, the investigation of this new technology is in its earliest stages. It has so far only been tested in mice injected with a highly metastatic strain of breast cancer, which caused very rapid tumour spread and development in these animals.

Animal studies can give a good indication of how a technology may work in people. But the two are not identical and many questions surround the research at this early stage.

Though the implant showed potential, we don't know it would work the same way in people. Even in mice, the implant didn't actually prevent metastases. The cancer still spread to other organs – the tumour burden was just less than when the implant was used.

This may mean disease progression would be slower, but indicates it couldn't completely stop it. The researchers say this could provide earlier detection of metastases so further treatment could be started, such as adjuvant chemotherapy.

We don't know whether the implant may have different effects on cancer spread by different routes. For example, the implant may have some effect in halting cancer spread through the bloodstream, but it may not prevent spread through the lymphatic system.

The researchers suggest the technology has the potential to be applicable to many types of cancer. But we don't know at this stage whether there may be certain cancers the implant would be more or less suitable for.

Practically, it is not yet known how the implant would be used in humans – for example, when they would be implanted, where in the body, and how long they would remain there. Importantly, it is also unknown whether there could be any adverse effects of using the implant, such as cancer spread.

Hopefully, the results of the upcoming clinical trials in people will shed light on these uncertainties.

Analysis by Bazian. Edited by NHS Choices. Follow NHS Choices on Twitter. Join the Healthy Evidence forum.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Implant 'traps' spreading cancer cells. BBC News, September 9 2015

Links to the science

Azarin SM, Yi J, Gower RM, et al. In vivo capture and label-free detection of early metastatic cells. Nature Communications. Published online September 8 2015

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