Observation Is the Best Course of Action for Benign Acoustic Tumors

Release: May 12, 2000
Contact: Kenneth Satterfield, 407-238-4161 (as of 5/12/2000)

NEW STUDY ASSERTS THAT OBSERVATION IS THE BEST COURSE OF ACTION FOR BENIGN ACOUSTIC TUMORS

Orlando, FL -- Acoustic neuromas are benign tumors of the cranial nerves commonly found in the elderly. In recent years, this condition is frequently diagnosed as the result of increasing usage of Magnetic Resonance Imaging (MRI) to evaluate a variety of neurological complaints. According to temporal bone studies, a one percent incidence exists for acoustic neuromas, whereas the observed clinical incidence is 0.00001 percent. To date, the medical management of these lesions in an elderly population is unclear.

Observation, surgical removal, and now gamma knife radiotherapy have each been advocated for the treatment of these tumors. Unfortunately, few studies have addressed the needs of the elderly patient population (>65 years), making comparisons between treatments difficult. Previous literature has relied on CT or tomograms for evaluation. Up to now, surgical management has been demonstrated to be a safe course of action for this population, but whether it is necessary at the entry point of diagnosis is not established.

Therefore, a study was undertaken to evaluate the efficacy of a conservative approach to acoustic neuroma in an elderly population followed exclusively by MRI. The authors of the study, "Acoustic Neuromas in the Elderly," are Brian Perry, MD, from The Otology Group of Texas, San Antonio, TX; and Bruce Gantz, MD, and Jay Rubenstein, MD, PhD, both from the Department of Otolaryngology, The University of Iowa, Iowa City, IA. Their findings were presented before the American Neurotology Society, which is meeting May 13-14 in Orlando, FL.

Methodology: The current policy at The University of Iowa is to observe acoustic tumors in the elderly (65 years of age and older), which do not cause significant brainstem compression. A retrospective case review was undertaken, to identify all patients over the age of 65 years with the diagnosis of acoustic neuroma. Patients who were seen prior to the advent of gadolinium enhanced MRI scanning were excluded from review, as were those with large tumors causing brainstem compression. Forty-one patients were identified meeting these criteria and selected for the study.

The subjects' charts were reviewed for age at diagnosis, facial nerve function, hearing status and tumor size. Each of these factors was re-evaluated at six months, and then yearly, unless rapid growth was encountered. Tumor size was measured in the largest dimension seen on gadolinium enhanced MRI. The presence of brainstem compression or hydrocephalus was similarly recorded. The endpoint was either the most recent clinical evaluation, or need for further intervention (surgery or radiotherapy).

Results: Forty-one patients were identified who were over the age of 65 years, and had received no prior treatment for their acoustic neuroma. Average age was found to be 70.8 years, with a range from 65 years to 94 years. The mean follow-up time was 42 months, with a median of 24 months.

Key findings include:

(1) Twenty-one (51.2 percent) tumors demonstrated growth during the follow-up period, at a mean rate of 0.322 cm per year. No growth was identified in 19 (46 percent) patients, while one patient (two percent) had a decrease in tumor size at a rate of 0.055 cm/year. No correlations could be made between tumor size at presentation and subsequent growth rate.

(2) Thirty-six patients (88 percent) were treated with observation only throughout the study period. The mean tumor size at presentation was 1.04 cm (range 2.5 mm B 2.5 cm). The mean length of follow-up in this group was 46 months (range 6 months B 120 months). One patient developed a grade II facial weakness during the observation period. Several patients had stable tumors for many years (5-7 years), with the subsequent development of tumor growth; none of these patients required intervention.

(3) No patients in the observation group developed hydrocephalus, or symptomatic brainstem compression. Hearing deteriorated in 20 percent of patients during the follow-up period (SRT elevation >10dB, or SDS decline > 10 percent). Hearing was preserved in 14 percent of patients, of these, 12 percent were unchanged, and in 2 percent it improved slightly. The vast majority of patients (66 percent) had no hearing loss at the onset of the study.

(4) Five patients (12 percent) required further intervention. Prior to further therapy, they were followed for a mean time period of 26.4 months, with a range from 18 months to 36 months. These patients demonstrated a mean growth rate of 0.456 cm per year, albeit with a large range (0.1 B 1.1 cm/year). The mean tumor size at presentation of this group was 1.78 cm (range 1.1 - 3cm). The indication for intervention was brainstem compression (without symptoms) in each of the five patients.

(5) During the observation period, 25 patients had significant hearing loss, while the others had a dead ear on presentation. None of these patients developed facial or trigeminal dysfunction. Three patients underwent uneventful complete surgical extirpation with preservation of facial nerve function (2 grade II, 1 grade I), while two underwent radiotherapy. Of the two patients who underwent radiotherapy, one died of unrelated causes shortly thereafter; the other was lost to follow-up.

Conclusions: The authors suggest that three treatment options are available for elderly patients with the diagnosis of acoustic neuroma: observation, surgical removal, and radiotherapy. When the tumor is large and causing symptoms of hydrocephalus or brainstem compression, the decision is quite simple. However when the tumor is small or medium sized, a recommendation can be difficult to make. The purpose of this study was to provide a guideline for management of these tumors in an elderly patient population. This study supports the use of an observation only protocol for management of small and medium sized acoustic tumors in the elderly. Repeat scanning at six months, and then yearly thereafter was endorsed. If the tumor remains stable for ten years or longer, scans at every other year could be considered.

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