The tumor itself, which generally stops growing but is not removed, may also contribute to hearing loss, said Dr. Bigelow. Even patients who have chosen to undergo observation rather than radiation will often experience hearing loss over time, even if the tumor does not grow, he said. The longer you watch with acoustic neuroma, the greater the chances that hearing will get worse, explained Dr. Bigelow.
Explore This IssueMay 2008
Factors Affecting Risk
The risk of hearing loss following stereotactic radiation depends partly on the radiation dose, said Dr. Young. We now use 12.5 Gy, he said.
Additionally, the better the patient’s hearing is prior to treatment, the better chance it will be preserved after radiosurgery, said Dr. Young.
The size of the tumor also plays a role in the risk of losing hearing, noted Dr. Bigelow. With radiation the best results occur with small tumors, he said.
Definition of ‘Loss’ Important
Risk of hearing deficits also depends on the definition of loss, said Dr. Coelho. For example, a drop of 1 decibel on pure tone average may result in a reclassification of hearing, depending on what scale is being used. Despite this drop, patients may continue to have serviceable hearing, he explained.
Likewise, preservation of hearing is a meaningless term if the pretreatment speech perception was poor, added Dr. Coelho. If there is no serviceable hearing to preserve, then losing it is not a risk. Critically analyzing the data and methodology used in reporting results is important.
He and his colleagues recently concluded that patients with acoustic neuromas less than 1.5 cm and no serviceable hearing, defined as word recognition score (WRS) of less than 50%, should receive surgical resection as the primary treatment if able to tolerate it, rather than stereotactic radiation. Their study of 57 patients, presented at the 2008 Triological Society Eastern Section meeting in January, found that surgery offered significantly better rates of disequilibrium and quality of life with respect to the patient’s disequilibrium.
A number of factors might prohibit a clinician from recommending stereotactic radiation, noted Dr. Coelho. For example, a tumor larger than 3 cm can result in clinically significant postradiation acute edema, he said.
Dr. House generally does not use stereotactic radiation on patients with tumors larger than 2.5 cm, and in those with cystic tumors or with vestibular symptoms.
In addition, patients with disabling vertigo or imbalance generally do poorly following stereotactic radiation, said Dr. Coelho.