WEDNESDAY, July 8 (HealthDay News) -- U.S. researchers report the first successful drug treatment of tumors in patients with neurofibromatosis type 2 (NF2).

In people with NF2, benign tumors develop throughout the nervous system. The most common tumor is a vestibular schwannoma, which grows on the nerve connecting the ear to the brain. This type of tumor, also called acoustic neuroma, causes hearing loss and can press on the brain stem, leading to serious neurologic symptoms and the risk of death.

Currently, these tumors are treated with surgery or radiation. This study found that treatment with the angiogenesis inhibitor bevacizumab (Avastin) shrank vestibular schwannomas, improved hearing and eased other symptoms in NF2 patients.

Bevacizumab is an anti-cancer drug designed to reduce blood flow to tumors in order to shrink them. But the drug wasn't used on acoustic neuromas because it was believed that they didn't stimulate formation of new blood vessels, as malignant tumors do.

But researchers at Massachusetts General Hospital in Boston analyzed tissue samples of NF2-related vestibular schwannomas and found evidence of excess blood vessel development. They then decided to test bevacizumab in 10 NF2 patients with vestibular schwannomas.

Tumor shrinkage occurred in nine patients, six of whom had a 20 percent or greater reduction in tumor size. The tumor shrinkage lasted between 11 and 16 months. Of the seven patients who had started to lose their hearing before treatment, four had some hearing restored. This improvement also lasted for up to 16 months.

"This kind of treatment response is unprecedented," lead author Dr. Scott Plotkin of the Pappas Center for Neuro-Oncology in the MGH Cancer Center, said in a news release. "Our study is the first to provide evidence that a drug can shrink vestibular schwannomas…and the first to show that patients' hearing can be improved."

The study will appear online in advance of publication in the July 23 issue of the New England Journal of Medicine.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about neurofibromatosis.