Cancer becomes significantly more deadly when it spreads throughout the body. Some types of cancers, like breast and prostate, are more likely to spread to the bones, and the spine is the most common site for those metastases. If doctors have to surgically remove a vertebrae, they can replace it with metal cages or bone grafts, which require an invasive surgery to implant, or they can implant titanium rods, which are less invasive to put in but are expensive.

Now researchers from the Mayo Clinic have created a spongy, expandable material that can take the place of cancerous vertebrae that have been surgically removed. They are presenting their work this week at a meeting of the American Chemical Society.

The researchers were looking to create a material that surgeons would be able to implant relatively non-invasively, so it would need to be compact, but also flexible enough to completely fill the empty space left by the missing vertebrae. And, ideally, it would be less expensive than the titanium rods, which can cost many thousands of dollars for just one patient.

So the researchers used a synthetic compound called oligo(poly(ethylene glycol)fumarate) that is often used in tissue engineering. It’s small enough that it can be inserted through a tiny incision, and once in the body, the spongy implant can absorb the body’s fluids so that it expands to fit the space from the vertebra. The researchers can change the material’s molecular weight and electrical charge to make sure that it doesn’t expand too quickly—otherwise, it could do damage to the body’s healthy tissues. The material can also be filled with compounds that will stabilize it in the body or with drugs, like those to fight cancer.

Experiments have shown the researchers that the material isn’t harmful to living tissues. Other spongy materials have been designed to work with the human body or to mimic its tissues. The researchers don’t mention whether the technology is able to help restore spinal function if it had been impaired, but their next plan is to test the material in cadavers, starting clinical trials in humans in the next few years.