Scientists at Duke University's Pratt School of engineering have used the ultrasound in animal studies to shake a tumor until its cells start to leak, triggering an “alarm” that enlists immune defenses against the cancerous invasion.

The study suggests that once activated, the immune system might even seek and destroy cancer cells that have spread to other parts of the body.

The high-intensity focused ultrasound, or HIFU, is in use or testing in China, Europe and the United States to kill tumors by heating them. But the Duke researchers discovered HIFU might be more effective if it's first delivered in a manner that ruptures tumor cell membranes, causing them to spill their contents, which, in turn, stimulates the immune system into producing tumor-fighting white blood cells.

If the effect seen in mice holds true in human trials, the procedure might become an important part of many cancer therapies since it can fight both primary and metastatic tumors without the need for surgery.

The study is reported in the Aug. 3 issue of the Journal of Translational Medicine.