Researchers at the University of Wisconsin-Madison have now developed an immunity-boosting hydrogel that can be injected into the brain after surgery to clear out remaining cancer stem cells.

The survival rates for glioblastoma are among the lowest of any cancer, with less than 5% of patients surviving five years after diagnosis. That's largely because this brain cancer has a tendency to come back after the tumor is surgically removed, as glioma stem cells are left behind to form new tumors.

"One characteristic of glioblastoma is that the tumor cells are very aggressive, and they will infiltrate the surrounding tissues," said Quanyin Hu, corresponding author of the study. "So the surgeon can't clearly feel the boundaries between the tumor and the normal tissue, and you cannot remove as much as possible because all the tissues in the brain are extremely important – you certainly don't want to remove too much."

But a new treatment might help turn the tide. The researchers have now developed a drug-laden hydrogel that can be injected post-operation into the space left behind after a tumor is removed. There, it gets to work training the immune system to hunt down any remaining glioma stem cells.

The hydrogel contains nanoparticles that can reprogram immune cells called macrophages, which flood the site after the surgery. Frustratingly, the tumor environment can make these macrophages switch sides, so they help promote cancer growth and suppress the immune response.