Tumor growth and audiometric change in vestibular schwannomas managed conservatively

Concordance of bilateral vestibular schwannoma growth and hearing changes in neurofibromatosis 2: neurofibromatosis 2 natural history consortium

OBJECTIVE

To examine the relationship between the amount of change in size and associated hearing in bilateral vestibular schwannomas (VSs) in persons with neurofibromatosis 2 (NF2).

STUDY DESIGN

Annual magnetic resonance imaging and audiological examinations were conducted on NF2 patients.

SUBJECTS

Fifty-two patients enrolled in the NF2 Natural History Consortium in whom both VSs were untreated. Magnetic resonance imaging and hearing exams were available for at least 2 time points 1 year apart. The 32 males and 20 females had a mean age at diagnosis of 26 years (SD = 18). In 19 (37%) subjects, the NF2 germline mutation could not be identified in the blood (mosaic).

OUTCOME MEASURES

Greatest diameter change in tumor size for each of the 2 tumors from first to second evaluation was determined. Differences in amounts of change between the 2 sides and in hearing (4-frequency pure-tone average) were evaluated using multivariate analysis of variance.

RESULTS

Overall, the VSs demonstrated significant average growth (p < 0.001), and hearing worsened significantly (p < 0.001) over 1 year. The amount of change in the bigger tumors was not associated with the amount of change in the smaller tumors within each patient. Vestibular schwannoma size changes were not associated with the corresponding hearing changes (Kendall's tau, p = not significant [n.s.]).

CONCLUSION

A significant 1-year change in VS size and hearing occurred in NF2 patients. Clinically, tumor change or hearing deterioration on one VS cannot be used to predict changes in the other VS. This suggests that, although NF2 is a Mendelian disease, the germline genotype-phenotype relationship may resemble that of complex disorders.

Diagnosis and therapy of vestibular schwannoma

MRI studies are of paramount importance for diagnosis and follow-up measurements during conservative and postinterventional management of vestibular schwannomas (VS). MRI findings that convey important information for hearing-preservation VS surgery are: length of tumor-cochlear nerve contact, involvement of the internal auditory canal, incomplete filling of internal auditory canal, tumor size less than 15 mm and the intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images. Functional neuro-otologic studies of facial nerve function, hearing and vestibular/balance function provide a valuable means of assessment of the actual impairment of the functional status of the VS patient. Intraoperative monitoring of facial nerve function and hearing has been refined, resulting in improved final postoperative facial nerve and hearing outcomes in VS patients treated with microsurgery. Long-term results reported by teams practicing stereotactic radiosurgery or fractionated stereotactic radiotherapy have been very encouraging. On the other hand, conservative management appears to be a viable option for a select group of VS patients. The refinement of surgical technique has rendered surgery safer and less invasive, resulting in better functional outcomes. Steroid use is currently used postinterventionally to improve final hearing outcome, although with questionable effectiveness. Physical rehabilitation programs are applied to accelerate vestibular functional recovery postoperatively and there is weak evidence that early physical rehabilitation may improve the final facial nerve outcome. Quality-of-life measures have emerged as important determinants of final therapeutic decision-making. More studies with high levels of evidence are needed to support clinical decisions.

Suggested response criteria for phase II antitumor drug studies for neurofibromatosis type 2 related vestibular schwannoma

Neurofibromatosis type 2 (NF2) is a tumor suppressor gene syndrome characterized by multiple schwannomas, especially vestibular schwannomas (VS), and meningiomas. Anticancer drug trials are now being explored, but there are no standardized endpoints in NF2. We review the challenges of NF2 clinical trials and suggest possible response criteria for use in initial phase II studies. We suggest two main response criteria in such trials. Objective radiographic response is defined as a durable 20% or greater reduction in VS volume based on post-contrast T1-weighted MRI images collected with 3 mm or finer cuts through the internal auditory canal. Hearing response is defined as a statistically significant improvement in word recognition scores using 50-word recorded lists in audiology. A possible composite endpoint incorporating both radiographic response and hearing response is outlined. We emphasize pitfalls in response assessment and suggest guidelines to minimize misinterpretations of response. We also identify research goals in NF2 to facilitate future trial conduct, such as identifying the expectations for time to tumor progression and time to measurable hearing loss in untreated NF2-related VS, and the relation of both endpoints to patient prognostic factors (such as age, baseline tumor volume, and measures of disease severity). These data would facilitate future use of endpoints based on stability of tumor size and hearing, which might be more appropriate for testing certain drugs. We encourage adoption of standardized endpoints early in the development of phase II trials for this population to facilitate comparison of results across trials of different agents.

REPEAT GAMMA KNIFE SURGERY FOR REGROWTH OF VESTIBULAR SCHWANNOMAS

OBJECTIVE

Gamma knife surgery (GKS) has become established as a minimally invasive treatment modality for patients with vestibular schwannomas. Treatment failure and/or tumor regrowth, however, is occasionally encountered, and microsurgical resection is usually warranted in such cases. The role of repeat GKS in these situations is still unclear. The goal of this study was to investigate whether repeat GKS is an effective treatment for recurrent vestibular schwannomas and to assess the conservation of residual neurological function.

METHODS

Between July 1992 and December 2007, 1951 patients harboring a unilateral vestibular schwannoma were treated with GKS. Of these, 48 patients (2.5%) had to undergo a subsequent intervention because of progression or regrowth of the tumor. Repeat GKS was performed in a total of 15 patients, 8 of whom had more than 2 years of follow-up and were eligible to be enrolled in the present study. The median follow-up period after repeat GKS was 64 months, and the median interval between these interventions was 46 months. The median tumor volume was 0.51 and 1.28 mL at the initial and second GKS treatments, respectively. Patients received a median prescription dose of 12.0 Gy at both interventions.

RESULTS

We report no cases of failure. Six patients demonstrated a significant reduction in tumor volume. In 1 patient, the final tumor volume was less than the initial volume. The other 2 patients showed stabilization of tumor growth. Useful hearing ability was preserved in only 1 of the 3 patients who had serviceable hearing ability at the time of the second GKS. Neither aggravation of facial nerve dysfunction nor other neurological deficits secondary to GKS were observed.

CONCLUSION

This is the first report to address repeat GKS for vestibular schwannomas. After long-term follow-up, repeat GKS with a low marginal dose seems to be a safe and effective treatment in selected patients harboring regrowth of small vestibular schwannomas that have previously been treated with GKS.

Vestibular Schwannoma: spontaneous tumor involution

The natural history of Vestibular Schwannomas (VS) is yet not totally known, but most of them have the tendency to slow growth, sometimes without any kind of symptoms during the individual's entire time. About 69% of diagnosed VS do not grow at all and 16% of these can even regress. Considering tumors that grow, about 70% have grown less than 2mm an year. Advanced radiological diagnosis, especially magnetic resonance imaging with gadolinium helps us diagnose small and less symptomatic tumors. Treatment of choice still is complete tumor resection. Surgical approaches have improved considerably and have helped preserve facial nerve function and hearing. Considering VS's natural history, there is a possibility for conservative treatment for these tumors, because their growth in the first year after diagnosis predicts tumor growth behavior in the next years. Surgery should be done in cases of tumor growth, patient's desire or symptoms worsening. Moreover, in terms of postoperative sequelae, there is no difference between patients who underwent surgery immediately after diagnosis and those who underwent initial conservative treatment for these tumors.

Hearing in patients with intracanalicular vestibular schwannomas

This paper reports data on the spontaneous course of hearing in 156 patients with purely intracanalicular vestibular schwannomas. The mean pure tone average (PTA) was 51 dB HL and the mean speech discrimination score (SDS) 60% at diagnosis. The risk of a significant subsequent hearing loss (>or=10 dB PTA or >or=10% SDS) was 54% during 4.6 years of observation. Patients with normal speech discrimination at diagnosis had a significantly smaller risk of loosing hearing. The hearing loss at diagnosis and during observation was not related to age, gender, diagnostic tumor size, tumor- induced expansion of the internal auditory canal or tumor sublocalization (fundus, central or porus). However, the loss of PTA was smaller in shrinking tumors and the PTA deterioration rate correlated with the volumetric tumor growth rate. After 4.6 years observation, the PTA had increased by 14 dB to 65 dB HL, and the SDS reduced by 17% to 43%. The proportion of patients eligible for hearing preservation treatment as determined by word recognition score class I (70-100% SDS) was reduced to 28% (a 44% reduction), and by AAO-HNS class A to 9% (a 53% reduction).

Use of ultra-high-resolution data for temporal bone dissection simulation

OBJECTIVES

For the past 5 years, our group has been developing a virtual temporal bone dissection environment for training otologic surgeons. Throughout the course of our development, a recurring challenge is the acquisition of high-resolution, multimodal, and multi-scale data sets that are used for the visual as well as haptic (sense of touch) display. This study presents several new techniques in temporal bone imaging and their use as data for surgical simulation.

METHODS

At our institution (OSU), we are fortunate to have a high-field (8 Tesla) magnetic resonance imaging (MRI) research magnet that provides an order of magnitude higher resolution compared to clinical 1.5T MRI scanners. Magnetic resonance imaging has traditionally been superb at delineating soft tissue structure, and certainly, the 8T unit does indeed do this at a resolution of 100-200 microm(3). To delineate the bony structure of the mastoid and middle ear, computed tomography (CT) has traditionally been used because of the high signal-to-noise ratio delineating bone signal from air and soft tissue. We have partnered with researchers at other institutions (CCF) to make use of a "microCT" that provides a resolution of 214 x 214 x 390 micrometers of bony structure.

RESULTS

This report provides a description of the 2 methodologies and presentation of the striking image data capable of being generated. See images presented.

CONCLUSIONS

Using these 2 new and innovative imaging modalities, we provide an order of magnitude greater resolution to the visual and haptic display in our temporal bone dissection simulation environment.

Systematic review of the natural history of vestibular schwannoma

OBJECT

Magnetic resonance (MR) imaging now permits diagnosis of increasing numbers of small, minimally symptomatic vestibular schwannomas (VSs). Because VS growth patterns over time are very important in refining treatment strategies, these matters were systematically reviewed.

METHODS

An extensive MEDLINE search was performed to cull studies on VS growth according to sequential imaging. The percentages of growing and regressing tumors and lesions requiring treatment during follow-up periods were calculated. Factors associated with differences among studies were identified. Twenty-six studies including 1340 patients met all inclusion criteria. The overall frequency of VS growth during a mean follow-up period of 38 months was 46% (95% confidence interval [CI] 43-48%) and that of regression was 8% (95% CI 6-10%). The mean annual tumor growth rate was 1.2 mm/year. Furthermore, the percentage of cases requiring treatment during follow up was 18% (95% CI 16-21%). According to results of a sensitivity analysis, evaluation by serial MR imaging (39%, 95% CI 35-43%) and a prospective study design (29%, 95% CI 21-37%) were associated with less frequent reported tumor growth.

CONCLUSIONS

Although their applicability may be limited to relatively elderly patients with small tumors, data revealing a limited frequency of VS enlargement and an infrequent necessity for eventual therapy should assist decision-making in the treatment of small VSs causing minimal symptoms.

Conservative Management of Acoustic Neuroma: A Meta-Analysis and Proposed Treatment Algorithm

OBJECTIVES/HYPOTHESES

Conservative management is a viable treatment alternative for acoustic neuroma. Using previous studies to provide evidence-based support, we have attempted to more clearly define the role of conservative management.

STUDY DESIGN

Retrospective review of literature and patient charts.

METHODS

Published studies on conservative management of acoustic neuroma were found using a key word search through PubMed in addition to the bibliographies of these selected studies. A spreadsheet was made to tabulate the selection criteria for conservative management, duration and frequency of follow-up, patient demographics, initial tumor size and rate of growth, change in hearing status, and the need for definitive treatment.

RESULTS

A total of 21 studies comprising 1,345 patients were included in our meta-analysis. The average length of follow-up these studies was 3.2 years. The average initial tumor size was 11.8 mm (n = 900); 43% of 1,244 acoustic neuromas showed growth, whereas 57% showed either no growth or tumor regression. The average growth rate was 1.9 mm/year in 793 individuals. Hearing loss occurred in 51% of 347 individuals. In 15 studies, 20.0% of 1,001 individuals eventually failed conservative management.

CONCLUSIONS

Our meta-analysis supports the role of conservative management of acoustic neuromas in properly selected patients on the basis of a slow overall rate of growth and a substantial incidence of no growth. However, the lack of predictive factors, the relatively short duration of follow-up, and the variability of inclusion criteria underscore the need for continued collection of long-term data. An algorithm for acoustic neuroma management is proposed based on initial tumor size, patient age, and hearing status.

Unilateral Acoustic Neuromas: Long-Term Hearing Results in Patients Managed with Fractionated Stereotactic Radiotherapy, Hearing Preservation Surgery, and Expectantly

INTRODUCTION

Hearing preservation is invariably a consideration when exploring treatment options for acoustic neuromas. We reviewed the long-term hearing results of patients who were treated using 1) hyperfractionated stereotactic radiotherapy (HSR), 2) hearing preservation tumor excision surgery (HPTES), and 3) expectantly (no treatment).

METHODS AND MATERIALS

Single institution retrospective chart review of 42 patients managed with HSR (1993-2003), 113 patients in whom HPTES was carried out, and 86 patients who were untreated (1974-2003). Hearing levels were graded according to the Gardner-Robertson classification.

RESULTS

The percent of patients managed with HSR initially who had serviceable hearing (class 1-2) was 68.8%. This fell to 6.7% in the follow-up interval. Of the group treated with HPTES, 100% had preoperative serviceable hearing. This dropped to 15.9% in the follow-up interval. The percent of patients managed expectantly who initially had serviceable hearing was 77.3%. This dropped to 33.3% during the follow-up interval. Mean follow-up periods were 4.0, 9.5, and 6.8 years in the HSR, HPTES, and expectant groups, respectively.

CONCLUSIONS

Hearing acuity statistically worsened over the long term (P < .01) in all three groups. There was a significant proportion of patients in whom hearing deteriorated from serviceable to nonserviceable hearing (P < .01) during the follow-up interval. The decline was most significant in the groups treated with HPTES and HSR compared with the group treated expectantly (P < .05). Hearing outcomes, in our experience, continue to be poor, but this is especially so in patients treated with HPTES or HSR.

Change in Hearing Handicap after Translabyrinthine Vestibular Schwannoma Excision

OBJECTIVE

To evaluate the change in hearing handicap after translabyrinthine vestibular schwannoma excision.

STUDY DESIGN

Prospective administration of the Hearing Handicap Inventory preoperatively and at 3 and 12 months postoperatively.

SETTING

A tertiary referral neurootology clinic.

PATIENTS

A total of 119 consecutive patients who had vestibular schwannomas excised between May 1998 and July 2002 and who had completed Hearing Handicap Inventories preoperatively and at 3 and 12 months postoperatively.

INTERVENTIONS

Translabyrinthine excision of a unilateral sporadic vestibular schwannoma; pre- and postoperative hearing therapy and rehabilitation.

MAIN OUTCOME MEASURES

Hearing Handicap Inventory scores.

RESULTS

Sixty-one percent of patients showed no change in their hearing handicap between preoperative and 3-month postoperative measures. Fifty-eight percent showed no change between preoperative and 12-month postoperative measures. Twenty-five percent of patients had a worsening in their hearing handicap when comparing preoperative and 12-month postoperative scores, and these patients were those with a better hearing class preoperatively. Seventeen percent of patients showed an improvement in their hearing handicap over this same time period, and the reasons for this remain unclear. Neither age nor tumor size had an effect on change in hearing handicap.

CONCLUSIONS

The findings of the current study can be used during preoperative patient counseling. In particular, the clinician is now able to take an informed and positive stance about the hearing handicap to be expected postoperatively.

Hearing deterioration in patients with a non-growing vestibular schwannoma

OBJECTIVE

The aim of this study was to document and analyse the course of several audiometric parameters in 49 patients with a non-growing unilateral vestibular schwannoma (VS).

MATERIAL AND METHODS

Patients received conservative management and absence of tumour growth was ascertained by means of serial magnetic imaging studies. Pure-tone audiometry and speech audiometry were performed at yearly intervals.

RESULTS

Pure-tone audiometry revealed a significant increase in thresholds at all frequencies, except for 8.0 kHz. The maximum yearly threshold increase was 2.4 dB hearing level at 1.0 and 2.0 kHz. Speech audiometry revealed a significant decrease in maximum discrimination over the course of time. No significant changes were observed in the following parameters: the intensity level at which maximum discrimination was achieved; the roll-over index; the speech reception threshold; and the slope of the curve in the speech audiogram. No change was observed in the relation between pure-tone audiometry thresholds and speech audiometry scores. Apparently, the deterioration of pure-tone perception and speech discrimination ran parallel courses.

CONCLUSIONS

The results of this study indicate that hearing loss is a predominant symptom in patients with a non-growing VS, as is also known in patients with a growing lesion. Moreover, it seems unlikely that the hearing loss in VS patients is merely the result of mechanical influences on retrocochlear neural or vascular structures.

Predictors of vestibular schwannoma growth in patients with neurofibromatosis Type 2

OBJECT

The results of two longitudinal studies of growth rates of vestibular schwannomas (VSs) in patients with neurofibromatosis Type 2 (NF2) differ as to whether VS growth rates decrease or increase with increasing patient age. The authors undertook this study to assess the relationship between VS growth rates and patient age and type of constitutional NF2 mutation; they also examined variability in VS growth rates among multiple patients in families with NF2.

METHODS

Gadolinium-enhanced magnetic resonance images obtained in 18 patients with inherited NF2 from 11 unrelated families were retrospectively analyzed. The patients had been observed for a median of 4 years. Volumes of the VSs were measured using a two-component box model (intrameatal and extrameatal parts measured separately). Single-strand conformation polymorphism analysis and Southern blot analysis were used to identify constitutional NF2 mutations. Growth rates of the VSs were highly variable, but tended to decrease with increasing patient age both at onset of signs or symptoms of NF2 (r2 = 0.35, p = 0.026) and at diagnosis (r2 = 0.33, p = 0.012). The VS growth rates did not vary significantly with the type of constitutional NF2 mutation or the number of non-VS cerebral or spinal tumors. The VS growth rates were highly variable within families and did not correspond to clinical indices of NF2 disease severity, such as patient age at symptom onset and the number of non-VS cerebral and spinal tumors.

CONCLUSIONS

The growth rates of VSs in patients with NF2 are highly variable, but tend to decrease with increasing patient age. Clinical treatment of multiple patients in families with NF2 cannot be based on the expectations of similar VS growth rates, even when other clinical aspects of disease severity are similar.

Tutorials in Clinical Research: Part III. Selecting a Research Approach to Best Answer a Clinical Question

OBJECTIVE

This is the third in a series of sequential "Tutorials in Clinical Research." The objectives of this specific report are to enable the reader to rapidly dissect a clinical question or article to efficiently determine what critical mass of information is required to answer the question and what study design is likely to produce the answer.

STUDY DESIGN

Tutorial.

METHODS

The authors met weekly for 3 months exploring clinical problems and systematically recording the logic and procedural pathways from multiple clinical questions to the selection of proper research approaches. The basic elements required to understand the processes of selection were catalogued and field tested, and a report was produced to define and explain these elements.

RESULTS

Fundamental to a research approach is the assembly of subjects and the allocation of exposures. An algorithm leading to the selection of an approach is presented. The report is organized into three parts. The tables serve as a rapid reference section. The initial two-part narrative explains the process of approach selection. The examples section illustrates the application of the selection algorithm.

CONCLUSIONS

Selecting the proper research approach has six steps: the question, logic and ethics,identification of variables, data display considerations, original data source considerations, and selection of prototypical approaches for assembly of subjects. Field tests of this approach consistently demonstrated its utility.