Treatment Options

The three basic options for treating an acoustic neuroma (VS) are Wait-and-Watch, Microsurgery, and Radiosurgery/Radiotherapy. The Acoustic Neuroma Association’s 2014 ‘Patient Survey’ showed percentages for these treatment choices for the 846 patients who participated: Wait-and-Watch (20%), Microsurgery (51%), Single-session Radiosurgery (17%), Multiple-session Radiotherapy (12%). When compared to ANA’s 1998 patient survey, these data revealed a significant increase for Radio-surgery/Radiotherapy (29% vs. 5%) and Wait-and-Watch (20% vs. 4%). There was a decrease in microsurgery: the patient survey in 1998 showed 85% for Microsurgery, compared to only 51% for 2014. ANA’s first survey in 1983 showed 100% for Microsurgery.

A Mayo Clinic report in 2015 observed that “one of the most significant recent advances in VS management has been the understanding that many cases of VS do not require treatment.” The report predicted that “by 2026, half of all cases of VS will be managed initially with observation” (Wait-and-Watch). The report recalled an optimistic prediction made in 1998 that more than two-thirds of newly diagnosed VS would eventually be treated with primary radiosurgery. But this prediction has not been realized. “While there has been a stable, slow decline in the use of microsurgery in favor of less invasive treatment, in recent years this volume has been increasingly allocated to observation rather than radiation therapy.” For the use of radiation for VS in the United States, “the current study demonstrates an apparent plateau.”

(See B.E.Pollack, L.D.Lunsford & G.Noren, “Vestibular Schwannoma Management in the Next Century: a Radiosurgical Perspective,” Neurosurgery, vol 43 (1998); J.Patel et al, “The Changing Face of Acoustic Neuroma Management in the USA: Analysis of the 1998 and 2008 Patient Surveys from the Acoustic Neuroma Association,” British Journal of Neurosurgery, vol 28 (Jan 2014) Free full text copy at PubMed.gov; M. Carlson, M. Link et al (Mayo Clinic), “The Changing Landscape of Vestibular Schwannoma Management in the United States – A Shift Toward Conservatism,” Otolaryngology-Head and Neck Surgery, vol 153(3) (2015).

Advisory

ANA/NJ believes that individual treatment is best decided by the informed patient in consultation with medical professionals who specialize in acoustic neuroma. New patients should consider the following:

Become familiar as soon as possible with all treatment options.
Consult with physicians who are Board certified and have extensive training and experience treating acoustic neuroma.
Consider treatment with physicians who present and willingly discuss all treatment options.
Consider treatment with physicians who use a team approach when treating acoustic neuroma.
Speak with other patients who have been treated for acoustic neuroma. Ask

physicians for names of patients they have treated. New Jerseyans especially may wish to consult ANA/NJ’s Directory (2020) for the names of patients willing to speak about their experiences with acoustic neuroma.

When researching on the internet:
1) Be careful using websites that do not offer information about all treatment options.
2) Avoid websites that obviously promote one type of treatment while disparaging others.
3) Evaluate whether or not the website is trying to make a sincere effort to present up-to-date information about treatment outcomes based on the peer-reviewed literature.
4) Be careful using websites that appear to promote individual physicians or particular hospitals or foundations.

Wait-and-Watch (Observation)

If an acoustic neuroma (VS) is small (< 1.5 cm) and symptoms for the patient are tolerable, a first option is to Wait-and-Watch by carefully monitoring the growth characteristics of the tumor with periodic MRIs.

Mutations causing sporadic VSs are known to vary from mild to severe, resulting in considerable variability in tumor growth behavior. Many small tumors do not grow at all. Some may grow at first and then shrink. Spontaneous shrinkage was observed in 3.8% of sporadic VSs during one reported period of Wait-and-Watch management. Although active treatment is generally recommended for tumors larger than 1.5 cm, it has been suggested that observation might be applied for VS patients with tumors up to 2 cm. (X.Huang, S.Stangerup et al, “Spontaneous Tumor Shrinkage in 1261 Observed Patients with Sporadic VS,” Jour Laryngol Otol, vol 127 (2013).

Wait-and-Watch (also called Wait-and-Scan) does not mean you are going to simply wait to see if the tumor will go away. Rather, it involves a personal commitment to “active surveillance” requiring interval MRI scans. Having an MRI about 6 months after diagnosis will help to determine whether a tumor is likely to continue to grow or is suitable for observation. In general, VSs grow very slowly with the average annual growth rate varying from 0.4 to 2.9 mm.

For the majority of small intrameatal (in the canal) tumors, the recommendation has been observation with yearly MRIs for five years, followed by decreasing frequency of observation if no growth has occurred. Any perceived growth needs to be watched closely to determine if or when active intervention should be considered. Danish studies have shown that hearing may decline during observation even though periodic MRIs indicate little or no tumor growth. Much depends on the quality of hearing at the time of tumor diagnosis.

ANA’s patient survey in 2014, reported that 63% of patients who chose to Wait-and-Watch said that they did so because their tumors were less than 1.5 cm. Besides small tumor size, acoustic neuroma patients may opt for “conservative management” because of advanced age, poor general health, minimal symptoms, or because the tumor is in the only or better hearing ear. The current “Treatment Options” section for ANA’s website calls attention to another important consideration: “All medical treatments, surgical or radiation, carry some risks. In time, safer treatments for acoustic neuroma, other than surgery or radiation, may be found.” A recent review of the medical literature by Drs. Zou (Changhai Hospital, China) and Hirvonen (Helsinki University, Finland) concluded that “the wait- and-scan management of VS is a safe method with the least problems and provides a better QOL for the patient than active treatments.”

(See Jing Zou & Timo Hirvonen, “Wait and Scan Management of Patients with Vestibular Schwannoma and the Relevance of Non-contrast MRI in the Follow-up,” Journal of Otology, vol 12(4) (December 2017). Free full text copy at PubMed.gov. See also the letter by Dr. John Rutka (Univ of Toronto) to his patient Judy Haust (President of the ANAC Board of Directors) regarding his advice to ‘Wait and Scan’ for her small IAC tumor: “To Judy: A Letter with a Purpose. Further Insights in the Conservative Management of a Vestibular Schwannoma,” The Connection (Summer, 2019), online at www.anac.ca/newsletters.)

Microsurgery

Surgical removal of an acoustic neuroma under general anesthesia is another option, especially appropriate for large or enlarging tumors causing serious problems in critical locations. Advances in microsurgical techniques and technologies, and the development of the medical surgical team approach, have greatly reduced the incidence of complications resulting from invasive intervention. Facial nerve preservation is being assisted by partial removals of large tumors followed by radiosurgery treatment of residual tumor. Long-term preservation of hearing remains an elusive goal. The best surgical outcomes are from medical centers with experienced acoustic neuroma teams.

There are three main surgical approaches used for removal of an acoustic neuroma. First, the translabrinthine approach is used for large tumors where preservation of hearing is not an issue. The incision is made in the hairline behind the affected ear and the tumor is exposed by removal of the mastoid bone. This results in total hearing loss in the affected ear. Facial nerve preservation, on the other hand, is facilitated by the approach. Minimal retraction of the brain is needed, which is good. Total removal of the tumor has been achieved in a high percentage of cases.

Secondly, for small tumors, the retrosigmoid (subocciptal) approach may help with preservation of hearing. The incision is behind the ear and an opening is made behind the mastoid part. There is retraction of the cerebeller portion of the brain. The risk of facial nerve damage is limited. The incidence of persistent postoperative headache has been reported as high, especially for small tumors (<1.0 cm), although recent modifications in microsurgical procedures have helped (e.g., greater attention to bone dust removal, craniopl asty rather than craniectomy).

Thirdly, for small tumors of 2.0 cm or less, the middle fossa approach may be used where hearing preservation is a major consideration. It is the least used of the three approaches. The incision is made above the ear with care to shave only a small area of the scalp. There is retraction of the temporal lobe of the brain, which may put stress on the temporal lobe’s memory circuitry. Possible damage to the facial nerve has been a major concern with this approach, although in recent years neural monitoring has improved functional outcomes. Long-term (ca. 10 years ) hearing preservation rates of 60-80% have been reported. Total tumor removal rates have been high.

(See Philip V.Theodosopoulos, “Surgery for Acoustic Neuromas: A Modern Day Paradigm,” ANA Notes, Issue 99 (Sept 2006); A.Monfared, “Treatment of Large Acoustic Neuromas and the ANSRS (Acoustic Neuroma Subtotal Resection Study),” ANA Notes (June 2016); S.Rahimpour et al (Duke Univ), “Microsurgical Resection of VS: Complication Avoidance,” Journal of Neurooncology, vol 130(2) (November 2016); R.Friedman & M.Schwartz (UC San Diego),“Post-Surgical Care Considerations for Acoustic Neuroma Patients,” ANA Webinar (August 5, 2019).

Radiosurgery & Radiotherapy

Radiosurgery and Radiotherapy are attractive treatment options for acoustic neuroma because they are non-invasive procedures that can usually be performed on an outpatient basis. Treatment is virtually painless and out-of-pocket costs for the uninsured are less than for microsurgery. The return to normal activities is usually immediate. The radiation technology and computer guidance involved today is very impressive and is being constantly improved. Patients do need to understand that tumors are not removed by radiation treatment; rather, the goal is to stop tumor growth, and possibly even reduce tumor size, by damaging cell DNA and destroying blood vessels in support of tumor cell growth. The main objective of “tumor growth control” has been achieved in 95-100% of cases. Pretreatment counseling should include the information that tumors often swell following radiation treatment, but this increase in size does not signal a failed procedure. However, since transient radiation-induced swelling of the tumor may occur, patients with large tumors (>3.0 cm) located near the brain stem may not be good candidates for radiation treatment. Microsurgery would be the appropriate first choice of treatment if tumor symptoms are acute or life-threatening. Surgical excision of the tumor may also be preferred by patients for personal reasons.

Radiosurgery is the delivery of a single, relatively high dose of radiation in a one-day session, whereas Radiotherapy involves multiple treatment sessions in which the total dose is spread over a few days or 3-4 weeks. Dividing the radiation dosage over time in this manner is called ‘fractionation.’ Thus we can speak of ‘fractionated stereotactic radiotherapy,’ or FSR, where the term stereotactic refers to the use of three-dimensional computerized target planning. Both FSR and stereotactic radiosurgery, SRS, use computerized planning for precise delivery of the radiation dose to the tumor while sparing surrounding normal tissue. Radiosurgery provides a more precise, concentrated effect, but may not be appropriate treatment if the tumor is very large or in a critical location. Radiotherapy, by splitting the total dose into fractions over time, may help with hearing preservation, although this advantage still remains to be determined.

The two main instruments used for Radiosurgery (SRS) are the Gamma Knife (gamma ray) and the Linac (X-ray). The Gamma Knife is a dedicated machine that was developed in Sweden specifically for brain abnormalities. It was first introduced in the U.S. at the University of Pitttsburgh in 1987. The newest, 6^th generation model, called “Icon,” is also capable of providing fractionated radiation treatment, if desired, and without the use of a skull-affixed stereotactic frame.

Gamma Knife

There are various versions of the Linac machine for providing both single-session Radiosurgery or multiple-session Radiotherapy. The CyberKnife protocol for acoustic neuromas developed at Stanford University has been unique for limiting radiation treatment to three fractions, called hypofractionation to distinguish it from the hyperfractionation of conventional radiotherapy. The recently developed “Edge radiosurgery system” by Varian, for example, uses a Linac for delivering high doses in a small number of fractions. Radiosurgery is beginning to be defined as any radiation treatment involving 1-3 fractions.

Proton Beam is a third external beam radiation device that is used for acoustic neuroma but has not been widely available because the technology is very expensive. Proton Beam treatment has typically been by hyperfractionation (e.g., 25-30 sessions over 5 weeks), although this protocol is currently under review.

(See “Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines on the Treatment of Adults with Vestibular Schwannomas,” Neurosurgery (February 2018), Online at www.cns.org/guidelines; D.Larson, “Acoustic Neuroma Today: From Traditional Radiotherapy to Stereo- tactic Radiosurgery,” ANA/NJ Newsletter, vol 16(2) (April 2018); J.D.Lipani, “Acoustic Neuroma Today: Hypofractionated Stereotactic Radiosurgery for Acoustic Neuroma: The CyberKnife,” ANA/NJ News-letter, vol 13(4) (June 2013); D. Smith et al, “Treatment Outcomes and Dose Rate Effects Following Gamma Knife Stereotactic Radiosurgery for VS,” Neurosurgery, vol 85(6) (Dec 2019), free full text at PubMed.gov; O.Persson,J.Bartek et al, “Stereotactic Radiosurgery vs. Fractionated Radiotherapy for Tumor Control in VS Patients: A Systematic Review,” Acta Neurochirurgica, vol 159(6) (April 2017), free full text at PubMed.gov).