One type of promising cancer treatment keeps falling short in humans — here’s what researchers think is the problem

Cancer cells

Using nanoparticles to attack tumours has long been seen as a promising approach to treating cancer.

The goal for nanoparticles is mainly to be used in drug delivery. In people with cancer, the cancer cells often get good at recognising the mechanisms the body is using to attack them. By throwing in a non-human element, the hope is to get the nanoparticle into the tumour so it can deliver medicine that will attack the cancer.

The treatment has succeeded in some limited cell and animal models. And it’s gained some celebrity backing: Futurist Ray Kurzweil, for example, wants to see programmable nanobots fighting off tumours, not just nanoparticles that carry a drug, Despite these gains, not a whole lot has translated into actual treatments in human clinical trials.

In a paper published Tuesday in Nature Reviews, researchers from the University of Toronto and the Beth Israel Deaconess Medical Center in Boston looked at existing studies on nanoparticle delivery to tumours. In the past 10 years, they found, only 0.7% of the nanoparticles typically get into the solid tumour.

Nanoparticles are super tiny particles that are made out of either organic or inorganic (think gold, silica, etc.) materials. And they face a lot of challenges on their way to getting into tumours. For example, the researchers noted, the nanoparticles are often escorted out of the body, diffused around the body, or stick to the surface of a protein instead of going within it.

To counter that small amount of nanoparticles actually making it to the tumour, one option is to pump more nanoparticles into the body. But then, the researchers pointed out, there are problems with toxicity in the body (not to mention costs associated with pumping more nanoparticles into the body).

Going forward, the researchers suggested a focus on how the body filters out or accumulates the nanoparticles before they reach the tumour, as well as learning more about how exactly the nanoparticles interact with the tumour, now that there’s been positive results. That way, the hope is to program the nanoparticles just the right way so they get to where they’re supposed to go.

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