Radiation Therapy for Acoustic Neuroma
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Acoustic neuromas, also known as vestibular schwannomas, are rare tumors found on the eighth cranial nerve. While surgical removal has been traditionally the preferred method for treating these types of tumors, recent data has supported the effectiveness of radiation and more specifically radiosurgery in controlling these tumors.
In addition, surgery is now more reserved for large tumors (more than 3 cm in diameter). Radiosurgery is also an effective option for patients whose tumor is not safely removable during surgery since the tumor is significantly adherent to the facial nerve and a small amount of tumor is left behind in surgery to protect the integrity of the nerve. Facial nerve paralysis is disabling and should be avoided. Small residual tumors from surgery can be effectively controlled via radiosurgery.
The patient may also be at an unacceptable risk to undergo surgery for acoustic neuroma. In these instances, radiation therapy may be a viable option to treat the tumor. To find out more about radiation therapy for an acoustic neuromas or vestibular schwannomas, please read on.
Radiation Therapy for Acoustic Neuroma (Vestibular Schwannoma)
Radiation therapy is used to destroy or control the growth of the cancer cells remaining after surgical excision. In the past, external beam radiation treatment (EBRT) was avoided when treating acoustic neuromas and for two reasons: 1) these tumors were thought to be resistant to radiation therapy and 2) vital cranial nerves, the brainstem, and other healthy tissues and structures were in danger of being damaged during the course of treatment.
In the last two decades or so, however, precise stereotactic radiotherapies and new imaging technologies have been developed so that brain tumors like acoustic neuroma may be treated with minimal damage to healthy surrounding tissues.
Radiation is now more commonplace and is performed by a comprehensive care team, often comprised of the following team members: a neurosurgeon and/or neurotologist, a radiologist, and a radiation oncologist. Depending upon the technology used, the patient's head may be secured in a frame to ensure it stays in the right position while the radiation is being delivered.
What Types of Precision Radiation Therapies are Available for Acoustic Neuroma?
Your medical team will choose the type of radiation treatment based upon various factors: the location of the tumor, patient's age, size and shape of the tumor, patient's symptoms, and any co-existing health problems. Also, some acoustic neuroma patients undergo radiation treatment after surgery to treat any pieces of remaining tumor that was unsafe to surgically remove.
Below are two common radiation therapies that top hospitals and clinics use to treat acoustic neuromas:
Stereotactic Radiotherapy (SRT)
Stereotactic radiotherapy utilizes real-time imaging with X-rays or CT scans during the radiation therapy. The use of real-time imaging helps ensure that there is less likelihood of any movement during the process in which the radiation is administered and that the best positioning is achieved. As a result, this type of treatment is delivered with great accuracy. During stereotactic radiotherapy, lower doses of radiation (fractions) are delivered over multiple treatments and typically over a larger area.
Stereotactic Radiosurgery (SRS)
Stereotactic radiosurgery is the type of radiosurgery in which the device called the Gamma Knife® is used at some institutions. Other institutions may use a different device such as the Varian TrueBeam® System, a linear accelerator that administers the radiation. Stereotactic radiosurgery is minimally invasive and extremely precise, delivering radiation directly to the targeted tumor.
Unlike traditional radiation therapy of the past, modern stereotactic radiosurgery has very little impact on the surrounding tissue and essential structures. During stereotactic radiosurgery, a single high dose of radiation is delivered to a smaller location.
Side Effects of Radiation Therapy for Acoustic Neuroma
The most modern techniques for delivering radiation therapy are highly accurate and have few noticeable side effects at first. However, some side effects may occur in the months and years following treatment. They include:
- Hearing loss: Whether or not hearing loss occurs after radiation therapy depends upon how much hearing the patient had before the treatment. Also, in the years after radiation treatment, hearing may gradually decline -- particularly for patients who had hearing loss before receiving radiation treatment, in older patients, or patients with larger tumors.
- Tumor expansion: Around six to 12 months after treatment, the tumor may increase slightly due to swelling. This is common and medical teams treating the tumor know that it is premature at that time to decide whether or not the treatment is successful.
- Cranial nerve damage (low risk): The possibility of cranial nerve damage is always a concern with radiation therapy for brain tumors. However, with modern radiation techniques, there is less than 5 percent chance of cranial nerve damage occurring.
- Possibility of developing a secondary cancer: A patient that undergoes any type of radiation therapy has a minimal risk of developing another cancer in the future. This is a risk that one normally faces with radiation exposure. This risk is 1/10,000, which is similar to people who never received radiation.
- Radiation treatment in the past 15 years has undergone vast technological improvements.
- Stereotactic radiosurgery uses a single high dose of radiation to treat an acoustic neuroma.
- Stereotactic radiotherapy uses multiple lower doses of radiation over multiple sessions.
- These methods provide radiation treatment in a highly targeted manner, with minimal effect to the healthy tissues and brain structures around the targeted tumor.
- Radiation therapy has the potential for side effects, including possible hearing loss, tumor expansion within the first year or so after treatment, and low risk of cranial nerve damage.