P16.34BEVACIZUMAB TREATMENT FOR ACOUSTIC NEURINOMA IN NEUROFIBROMATOSIS TYPE 2: A CASE REPORT.

Neurofibromatosis type 2 (NF2) is a dominantly inherited genetic condition. Unlike patients with sporadic tumours, NF2 patients often have multiple meningiomas, acoustic neurinomas and ependymomas. The multiplicity of tumours make surgery and radiation therapy for all tumours impracticable. In effect, bilateral acoustic neurinomas are the hallmark of this disease and these tumours cause progressive hearing loss in most patients. Neovascularization is necessary for tumour growth and is driven by tumour produced angiogenic factors such as vascular endothelial growth factor (VEGF). Bevacizumab is a humanized monoclonal antibody that neutralizes the activity of VEGF. Recent data showed that VEGF is produced by schwannoma tumour cells. Also, bevacizumab treatment, in patients with NF2 who were considered poor candidates for surgery and radiation therapy, was followed by clinically meaningful hearing improvement and tumour-volume reduction. We report the case of a 39 years old woman with sudden rightsided hearing loss. Magnetic resonance imaging (MRI) revealed multiple meningiomas and neurinomas (C2 and L5 lesions) and a right side acoustic neurinoma of 26x24 mm, confirming the diagnosis of NF2. Bevacizumab was given as an infusion every 2 weeks at a dose of 5.0 mg/kg body weight. Before the treatment, the patient has a thorough medical evaluation including blood pressure, urine analysis, liver and kidney function tests, coagulation status and history of thrombosis, hemoglobin, leukocyte count and thrombocyte count. Three months after the start of therapy the patient has reported an hearing response with progressive improvement in audiometry, word recognition and face-to-face conversation. Six months after the start of therapy, the right acoustic neurinoma had regressed and, also, mitigation of brain stem compression was clearly visible on the cranial MRI scans. The patient, after 12 months, continued to be treated with bevacizumab. In our experience no toxic effects drug-related has been seen; anyway, the absence of many common toxic effects of bevacizumab in our patient may have reflected her youth and the lack of other medical conditions. The exact mechanism of the action of bevacizumab on acoustic neurinomas remains to be elucidated. The drug may also suppress growth of tumour Schwann cells directly, a possibility that can be tested in vitro in future studies. The encouraging results with bevacizumab suggest consideration of a prospective clinical trial for progressive NF2-related acoustic neurinomas, especially for patients with imminent total hearing loss.