A rodent "backpack" could speed up cancer drug discovery

Without preclinical testing, we wouldn’t have today’s life-saving cancer drugs. After all, scientists need to make sure a treatment works in animals before they can test it on people.

This stage of testing can be slow and laborious, but a new device developed by Stanford University researchers aims to expedite the screening process and bring these drugs to patients more quickly. The team reported their findings in a recent study published in the journal Science Advances.

Here’s the background — During the testing stage, scientists track tumor size over time to see if cancer drugs are effectively shrinking them. But it’s a costly and labor-intensive undertaking.

Not to mention that some of the commonly used techniques are relatively low-resolution and can’t detect small changes in tumor size, says Alex Abramson, a study co-author and biomedical engineer at the Georgia Institute of Technology.

All in all, it takes a relatively long time for scientists to separate successful drugs from the duds.

What’s new — When Abramson was working on his post-doc research at Stanford, he and his colleagues decided there had to be a better way to tell whether drugs work. That’s why they created the Flexible Autonomous Sensor measuring Tumors (FAST) device to examine masses that lie just below the skin.

The non-invasive device avoids the arduous process of surgically implanting sensors in lab animals. Instead, the sensor consists of a very thin layer of gold spread over a stretchy polymer, which is wrapped around a tumor over the skin. As the tumor grows or contracts, tiny cracks in the layer of gold shift as well, changing the electrical resistance and allowing for highly precise measurements of tumor size.

“This sensor has a resolution of about 10 microns in terms of the changes that we can detect in the tumor volume,” Abramson says. “That's on the order of a single cell.”

This level of precision enables the sensor to gauge a drug’s efficacy astonishingly quickly: Just five hours after mice were given an established cancer therapy, the FAST device revealed differences in the tumors of treated mice versus mice that hadn’t received the treatment.

Why it matters — This continuous, highly detailed monitoring helps researchers understand how a certain dose affects tumor regression, Abramson says, or when another dose might be necessary.

“I think this is very interesting work,” says Wei Gao, a medical engineer at the California Institute of Technology who was not involved in the study. “Tumor progression is very important to monitor and there is no good way right now to do this in real-time … This could potentially have a very high impact in cancer therapy.”

The sensor also makes drug screening much simpler. It’s housed in a tiny backpack continuously worn by the mouse and wirelessly sends measurements to a smartphone app. So once the nifty device is attached, researchers don’t need to handle the mouse (or even be in the same building) to gather information.

“It's totally automated — you put this backpack on the mouse and you can set it and forget it,” Abramson says. “That's something that's really exciting for researchers, that you can really scale up the number of studies that you're working on because you don’t have to spend as much time on a specific one.”

The device is also relatively cheap. The entire package, including all the electronics, costs about $60, according to Abramson.

What’s next — For now, Abramson says that the device is intended for preclinical testing (i.e. in animals). But similar technology could eventually be used to monitor tumors in human patients.

“It definitely has the possibility to be used in humans, although that would require surgical implantation,” he explains. “We're working on a new version of the sensor that can be surgically implanted, but we need to do some more miniaturization to reach that goal.”

Implanted devices come with a whole new set of challenges, Gao notes, including making sure they’re compatible with human tissues over the long term. It’s also tough to figure out how the device will be powered. Nevertheless, he says, “I’m very excited by this technology.”