(AP) -- Medical device maker Novocure says it has received U.S. approval for a first-of-a-kind treatment which fights cancerous brain tumors using electrical energy fields.

The Food and Drug Administration has approved the device for patients with aggressive brain cancer that has returned after treatment with chemotherapy. Patients with recurring brain cancer usually live only a few months.

For decades doctors have treated cancer with drugs, and surgery. Novocure's NovoTTF offers a fourth approach. The portable device uses electric fields to disrupt the division of that allows tumors to grow. It sends the signals through four electrodes which are taped to the patient's head.

A 237-patient study showed that people using the device lived about as long as those taking . However, patients had significantly fewer side effects.