Acoustic neuroma is a rare, non-malignant, and passively growing tumor of the brain. It is otherwise called vestibular schwannoma, acoustic neurilemmoma, acoustic neurinoma, and neurofibroma of the acoustic nerve. This tumor usually develops in the eight cranial (auditory/vestibulocochlear) nerve and engages the cerebellopontine angle. It accounts for 80% of cerebellopontine angle tumors and 6% of all tumors that arise in the brain.
Acoustic neuroma and neurofibromatosis?
Acoustic neuromas are usually of two types, sporadic unilateral and genetic bilateral. The unilateral type arises from sudden and nonhereditary mutations, occurs on one side of the body, and is commonly seen in adults. On the other hand, the bilateral type occurs on both the sides of the body, is commonly seen in children, and is associated with Neurofibromatosis II, a rare genetic disorder that causes tumors in the brain, spinal cord, and nerves.
Do you know about bevacizumab?
Bevacizumab, available under the trade name Avastin® is a monoclonal antibody that is synthesized from the cells of the immune system. It is categorized in a group of drugs called vascular endothelial growth factors (VEGF) inhibitors.
What might be the action of bevacizumab on acoustic neuroma?
Bevacizumab selectively binds the vascular endothelial growth factor (VEGF) that is circulating in the blood and blocks its action.
It is an antiangiogenic agent, which inhibits the formation of new blood vessels that transports nutrients, and oxygen to tumor cells along with the blood.
Due to the diminished blood supply, the tumor cells become necrotic and the tumor starts shrinking.
This mechanism makes it suitable to use for many types of cancers along with antineoplastic agents.
It is used in tumors like acoustic neuroma, and cancers like metastatic cancer, colorectal cancer, small lung cancer, renal cell cancer, peritoneal cancer, ovarian cell cancer, and recurrent glioblastoma.
Adverse effects include fatigue, hair loss, decreased white blood cell count, high blood pressure, and inflammation of the mouth or throat, numbness or tingling sensation in hands or feet.
It is not given in patients undergoing surgery or pregnant women due to the increased risk of bleeding.
Current management strategy using bevacizumab in acoustic neuroma
Management of acoustic neuroma depends upon the age of the patient, the size of the tumor, and symptoms that are present at the time of diagnosis. It includes wait and rescan, pharmacological therapy for the remission of symptoms, surgical excision, radiotherapy, and stereotactic radiosurgery. But surgical excision and radiotherapy have their limitations like damaging the adjacent nerves and surrounding structures like the cerebellum, and brain stem resulting in permanent hearing loss, and also other unavoidable complications like post-surgical trauma, and radiation exposure. They are also associated with recurrence even after treatment. So the administration of pharmacological agents can be considered as an alternative in the treatment of an acoustic neuroma. Drugs can be given in acoustic neuroma for the relief of symptoms. Based on advanced studies, molecular inhibitors which inhibit different growth factors that act in the pathogenesis of acoustic neuroma can also be considered. But despite being effective on tumor growth, they are associated with several side effects . One such molecular inhibitor that can be used in acoustic neuromas is bevacizumab. Studies have proved that the administration of bevacizumab in acoustic neuroma results in hearing improvement in patients due to the shrinkage of tumors because of its anti-angiogenic property. It has also been proved that it is particularly effective in bilateral acoustic neuromas, which are seen in association with neurofibromatosis II, a condition commonly seen in children. So bevacizumab can be given in patients with acoustic neuroma along with antineoplastic agents.
Ideas for better health
The anti-angiogenic property of bevacizumab justifies its role in reducing the symptoms of acoustic neuroma and it can be considered as a replacement option for surgical excision and radiotherapy, in case of small tumors. But the adverse effects of bevacizumab should be kept in mind while indicating it and further research is necessary regarding this aspect.
V. K. Gupta, A. Thakker, and K. K. Gupta, “Vestibular Schwannoma: What We Know and Where We are Heading,” Head Neck Pathol., vol. 14, no. 4, pp. 1058–1066, Dec. 2020, DOI: 10.1007/s12105-020-01155-x.
M. C. Alanin et al., “The effect of bevacizumab on vestibular schwannoma tumor size and hearing in patients with neurofibromatosis type 2,” Eur. Arch. Oto-Rhino-Laryngol. Off. J. Eur. Fed. Oto-Rhino-Laryngol. Soc. EUFOS Affil. Ger. Soc. Oto-Rhino-Laryngol. - Head Neck Surg., vol. 272, no. 12, pp. 3627–3633, Dec. 2015, DOI: 10.1007/s00405-014-3398-3.
J. Long, Y. Zhang, X. Huang, J. Ren, P. Zhong, and B. Wang, “A Review of Drug Therapy in Vestibular Schwannoma,” Drug Des. Devel. Ther., vol. 15, pp. 75–85, 2021, DOI: 10.2147/DDDT.S280069.
S. R. Plotkin et al., “Hearing Improvement after Bevacizumab in Patients with Neurofibromatosis Type 2,” N. Engl. J. Med., vol. 361, no. 4, pp. 358–367, Jul. 2009, doi: 10.1056/NEJMoa0902579.