A small sponge-like implant that can mop up cancer cells as they move through the body has been developed by US researchers. So far tested, it is hoped the device could act as an early warning system in patients, alerting doctors to cancer spread.

The implant also seemed to stop rogue cancer cells reaching other areas where new tumours could grow. The findings appear in Nature Communications.

Cancer Research UK said nine in 10 cancer deaths were caused by the disease spreading to other areas of the body.

About 5 mm (0.2 in) in diameter and made of a "biomaterial" already approved for use in medical devices, the implant has so far been tested in mice with breast cancer.

Experiments showed that implanting the device in either the abdominal fat or under the skin sucked up cancer cells that had started to circulate in the body.