Dr. Daspit again emphasized that more long-term data are required and strongly urged otolaryngologists, otologists, and neurotologists to become actively involved in treating patients.
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January 2008Evidence Base
Current data on stereotactic radiation therapy using contemporary dose regimens of 12-13Gy to the tumor margin were presented by Robert Jackler, MD, who is Sewall Professor and Chair of the Department of Otolaryngology, Head and Neck Surgery at Stanford University. He presented a meta-analysis drawn from dozens of articles in the recent literature. This included a substantial number of patients with follow-up periods greater than five years.
In terms of natural history, 55% of untreated acoustic neuromas demonstrate growth over a three-year period. He said that 90% to 95% of sporadic small tumors are controlled over the long term with stereotactic radiotherapy at current doses. Outcomes are poorer in larger tumors, which have a regrowth rate of 30% and a higher risk of radiation-induced brain injury.
For neurofibromatosis type 2 tumors, control rate is only about 70%, and is possibly even lower in younger patients.
According to reports from 2000 through 2007, in patients with Gardiner-Robinson grade 1 or 2 hearing before radiation, there is a 60% chance of preservation at five years, he continued. Hearing preservation is possible in only about 35% of patients with neurofibromatosis type 2, he added.
Facial palsy is rare with current stereotactic radiotherapy doses, although transient facial twitch was reported in a small percent of patients six to eight months following treatment. The primary risk of facial injury occurs when surgery is used following recurrences after stereotactic radiotherapy, Dr. Jackler commented.
Surgical salvage of radiation failure carries a higher complication rate than primary surgery. The converse is not true, however, as radiation salvage of surgical remnants works as well as primary stereotactic radiation. This has led to the exploration of combined therapy, in which large tumors are subtotally removed and the remnant radiated if it shows growth over time.
According to reports from 2000 through 2007, in patients with Gardiner-Robinson grade 1 or 2 hearing before radiation, there is a 60% chance of preservation at five years.-Robert Jackler, MD
Secondary malignancy after stereotactic radiotherapy remains a concern, but Dr. Jackler suspects that the incidence is likely to be low. Nevertheless, whenever considering radiation for a benign tumor, the potential of inducing a lethal malignancy years later must be discussed with the patient. Longer-term follow-up is needed to determine the actual incidence of lethal malignancy.