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Study explores risk factors for acoustic neuroma growth

Aug. 23, 2018, 10:07 AM


Surgeons face a delicate proposition when treating acoustic neuromas, benign tumors on the nerve that affect hearing and balance. Removing small tumors through surgery and radiation can cause complications such as the loss of hearing, when the tumors may not grow and impact quality of life for years. But not removing them can allow them to grow and be more difficult to remove and pose even greater risks.

A Vanderbilt study of acoustic neuromas that is the largest ever published on the subject sought to explore which of the tumors were more likely to grow and need removal, and which ones could remain under observation with little growth and associated symptoms.

The latest of a series of three Vanderbilt papers on the subject, which was recently published in the journal Otology & Neurotology, studied 564 people with such tumors. It found that larger tumors were more likely to grow, while smaller ones may be safely left under observation for years.

“We found that the only predictors of growth were not patients’ ages, but rather the presenting size of the tumor and whether or not they had imbalance as a symptom,” said David Haynes, MD, professor of Otolaryngology, Neurosurgery and Hearing and Speech Sciences, one of the study’s authors.

The findings have major implications on treatment, as smaller tumors are routinely removed under current practice. They allow doctors to offer precise, personalized care to patients.

“This study is incredibly important because when a patient is diagnosed with a brain tumor, they are terrified, and their first reaction is to want the tumor treated immediately,” said Reid Thompson, MD, William F. Meacham Professor of Neurological Surgery and chair of the department.

“Developing a plan with patients requires a careful balance of risk and benefits. This study helps to clarify the decision-making with patients and avoids exposing patients to unnecessary risk.”

“This extensive 20-year study gives us more information and allows us to make better decisions for patients,” Haynes added. “For example, if our observation determines that a tumor is rapidly growing, we will use that information to select the appropriate intervention. The growth rate would determine which mode of intervention is best suited for a particular patient. A slow-growing tumor may not require intervention immediately, or possibly at all.”

Acoustic neuromas, also known as vestibular schwannomas, are tumors on the eighth cranial nerve, which controls hearing and balance. It stretches from the inner ear to the brain stem.

The study found that 50 percent of tumors measuring 2 centimeters or greater grew by nine months. However, tumors a half-centimeter or less took 77 months to grow by 2 millimeters.

Patients with disequilibrium had a 70.2 percent increased risk of tumor growth compared to those without the symptom.

The studies also looked at the hearing of the patients with small tumors.

For those patients whose tumors were observed, 94 percent had preserved their hearing in a year, 65 percent maintained it after five years and almost 50 percent had hearing preservation at 10 years.

Haynes said the data shows that observation may be the best course to preserve hearing for patients in select circumstances. “Following certain patients gives us information on growth rates and allows us to make better decisions on care and achieve better outcomes.”

He stressed that Vanderbilt remains a world-class destination for skull base surgery, especially acoustic neuroma surgery, by providing unique multidisciplinary care and the latest innovative technique.

He added that surgery remains an important choice for many as an initial option or if observation demonstrates growth. But the study underscores the importance of observation for patient-specific information regarding need for and timing of surgery.

“The results reinforce that active surveillance offers a subgroup of patients a new, valid option,” said Ron Eavey, MD, Guy M. Maness Professor and chair of Otolaryngology and director of the Vanderbilt Bill Wilkerson Center. “The magnitude of the study indicates the exceptional capability of the members of our Vanderbilt Skull Base Team and their global impact.”

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