Acoustic neuroma medical therapy

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2] Mohsen Basiri M.D.

The mainstay of therapy for acoustic neuroma is surgery and radiation therapy. Since acoustic neuroma tends to be slow-growing and is a benign tumor, careful observation with follow-up MRI scans every 6 to 12 months may be appropriate for elderly patients, patients with small tumors, patients with significant medical conditions, and patients who refuse treatment.

The mainstay of therapy for acoustic neuroma is surgery and radiation therapy. Since acoustic neuroma tends to be slow-growing and is a benign tumor, careful observation with follow-up MRI scans every 6 to 12 months may be appropriate among the following groups of patients:^[1][2]

• Patients with a tumor in their only hearing or better hearing ear
• When the tumor is of a size that hearing preservation with treatment would be unlikely
• Elderly patients
• Small tumors in older individuals that do not grow
• Patients with small tumors with good hearing
• Patients with medical conditions that increase the risk of complications of surgery
• Patients who refuse treatment
• Patients with a tumor on the side of an only hearing ear or only seeing eye

The strategies for patient observation include:

• Assessment of facial nerve function, hearing, tinnitus, and ataxia.
• An MRI is performed every 6 months or yearly depending on the rate of tumor growth.
• The average growth rate of tumor is 1.15 to 2.4 mm per year. If the tumor grows or causes serious symptoms, treatment is suggested. If the scans show tumor growth or if the tumor causes progressive symptoms or other difficulties, considering surgical intervention is mandatory. ^[3]

Radiation therapy approaches that have been used in patients with acoustic neuroma include:

• Stereotactic radiosurgery
• Stereotactic radiotherapy
• Proton beam therapy

Stereotactic radiosurgery (SRS), is a treatment option for patients with tumors smaller than 3 cm or for enlarging tumors in patients with significant medical conditions and are not candidates for surgery. It delivers multiple precisely-targeted radiation convergent beams to minimize injury to adjacent structures. This can be accomplished with either the gamma knife or a linear accelerator.^[4][5]

• Stereotactic radiotherapy (SRT) and fractionated stereotactic radiotherapy deliver smaller doses of radiation over a period of time, requiring the patient to return to the treatment location on a daily basis, from 3 to 30 times, generally over several weeks.

• Each visit lasts a few minutes and most patients are free to go about their daily business before and after each treatment session.
• Early data indicates that SRT may result in better hearing preservation when compared to single-session SRS.^[6]

• The use of proton beam therapy permits the delivery of high doses of radiation to the target volume while limiting the dose received by surrounding tissues. It provides maximum local tumor control with minimum cranial nerve injuries.^[7]
• In comparison with conventional radiation therapy where electromagnetic waves in x-rays pass through target and adjacent tissues, in proton beam therapy, energy is carried by proton beams and the majority of the energy being deposited within the target.
• It provides excellent local control of acoustic neuromas with acceptable preservation of hearing and facial and trigeminal nerve function.^[8]

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