Bevacizumab decreases vestibular schwannomas growth rate in children and teenagers with neurofibromatosis type 2

Vestibular schwannoma (VS) growth in neurofibromatosis type 2 (NF2) can be responsible for brainstem compression and hearing loss. Surgical removal remains the standard therapy despite potential morbidity. Previous studies suggested that the inhibition of the VEGF-pathway with bevacizumab could result in hearing improvement, reduction of the tumor volume or both in adults. We retrospectively describe the French experience of bevacizumab treatment delivered for progressive VS in pediatric NF2 patients. Patients received Bevacizumab 5 or 10 mg/kg every 2 weeks according to the physician's choice. Follow-up included clinical assessment, audiometry and volumetric MRI every 3-6 months. Seven patients harboring 11 VS were included. The median age at inclusion was 15 years (11.4-18.8), and the median treatment duration was 11.3 months (3.2-55.6). At baseline, the median tumor volume was 1.2 cm(3) (0.52-13.5) and the median word recognition score was 90 % (0-100). We observed one major response, two minor responses and a decrease in the rate of tumor growth for the 4 other patients. The median annual growth rate before treatment was significantly higher than after 1 year of treatment (138 vs. 36 %, n = 5, p = 0.043). We noted one hearing improvement over the course of 1 year under treatment (hearing response rate was 14 %). Overall, the treatment was well tolerated. Our study supports that bevacizumab is an attractive therapeutic option for pediatric NF2 patients with growing VS. Thorough multidisciplinary evaluation is necessary to identify the best candidates prior to treatment. It is likely that a better functional outcome would be expected if targeted therapies were discussed early in the management of the disease.