Catching Cancer Cells November 2015
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Current cancer treatment can be effective in treating the primary tumor, but a danger always exists that secondary tumors will form. A study led by researchers at the University of Michigan shows that a subcutaneous implant of a sponge-like biomaterial will attract and hold cancer cells from a primary tumor that are circulating in the body. The work, which appeared in the September 2015 Nature Communications, is at an early stage, and the researchers have yet to test the biomaterial in humans, but their studies in mice show that cancer cells infiltrate the implant and the test animals develop fewer secondary lesions than the control group develops. The 5 mm-diameter implant is porous poly(lactide-co-glycolide), a biomaterial that already has approval for use in the body.
The researchers suggest that the implant itself triggers an immune response and attracts immune-system cells. Residing in the material, these immune cells then "capture" circulating metastatic cancer cells and hold them in the porous scaffold. Postmortem examination of the animals' organs shows that animals with the implant have a tenfold reduction in the tumor burden on other solid organs.
Although research to develop technologies that detect circulating cancer cells is in progress, scientists have yet to deliver an effective early-identification system. Using a simple and well-tested biomaterial, the University of Michigan researchers have the beginnings of a system that they hope will offer a means to monitor the presence of metastasizing cells. The focus of the animal study was a breast-tumor model, and further work will need to demonstrate that the implant is effective in detecting the spread of other cancers, which may spread through either the blood or the lymphatic systems.
The second effect of the implant is to reduce the incidence of cancerous cells at secondary sites. Mice that received the implant showed 5,400 healthy cells at a secondary site to 1 cancerous cell. In comparison, the ratio was 645 to 1 in mice without the implant. If studies in humans show the implant is effective at capturing a range of cancer cells and reducing the level of cancer cells at secondary sites, the system could be highly effective in complementing initial cancer therapy.
The study authors say, "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." Health-care providers will take a keen interest in any technology that enables early identification and treatment of metastatic disease: It is not the primary tumor that kills; it is the secondary tumor that does so. According to Cancer Research UK in the BBC News article about the device, the spread of cancer cells from the primary site to the secondary site is responsible for nine in ten deaths resulting from cancer.