Volume growth rate of acoustic neurinomas

Spontaneous shrinkage of vestibular schwannoma with the recovery of impaired hearing: A case report and literature review

Background

Sporadically occurring vestibular schwannomas (VSs) are the most frequent tumors in the cerebellopontine cistern and internal meatus and are commonly associated with hearing loss. These tumors have demonstrated spontaneous shrinkage rates of 0-22%; however, the relationship between tumor shrinkage and changes in hearing remains unclear.

Case Description

We report a case of a 51-year-old woman with a diagnosis of a left-sided VS and accompanying moderate hearing loss. The patient was treated with a conservative approach for 3 years, and the tumor showed a regression along with an improvement in her hearing ability during the yearly follow-ups.

Conclusion

The spontaneous shrinkage of a VS along with an associated improvement in hearing is a rare phenomenon. Our case study may support that the "wait and scan" approach is an alternative option for patients with VS and moderate hearing loss. Further investigations are needed to understand spontaneous VS regression and hearing changes.

Evaluating growth trends of residual sporadic vestibular schwannomas: a systematic review and meta-analysis

BACKGROUND

Gross total resection remains the gold-standard approach for vestibular schwannomas (VS) when surgery is indicated. In select cases, incomplete resection (IR) becomes a desired alternative to preserve the facial nerve function and the patient's quality of life. While a lot of earlier studies described incompletely resected sporadic VSs as dormant, more recent studies reported a higher growth rate following IR, therefore an evaluation of the residual VS growth rates could have important implications for the follow-up treatment protocols and provide relevant information for neurosurgeons, neuro-otologists, neuropathologists, and radiologists. Although prognostic factors predicting preoperative VS growth have been previously investigated, these factors have not been investigated following IR. Our review aims to examine the growth rate of residual sporadic VS following IR and to examine variables associated with the regrowth of residual VS.

METHODS

The review was conducted in accordance with the PRISMA guidelines. Six databases (MEDLINE (Ovid), Embase (Ovid), CINAHL Plus (EBSCO), Cochrane Central Register of Controlled Trials (CENTRAL), WHO International Clinical Trials Registry Platform and UK Clinical Trials Gateway (WHO ICTRP) were searched. Full-text articles analysing growth rates in at least ten patients who had residual VS after IR were assessed. We conducted a meta-analysis using a random-effects model via RevMan.

RESULTS

14 studies totalling 849 patients were included in the analysis. The mean planimetric growth rate was 1.57 mm/year (range 0.16-3.81 mm/year). The mean volumetric growth rate was 281.725 mm³/year (range 17.9-530.0 mm³/year). Age, sex, pre-operative tumour size/volume, cystic tumour sub-type, MIB-1 index, and intracanalicular tumour location were not associated with residual growth. Residual tumour size/volume was statistically significant to growth (OR = 0.65, 95% CI 0.47-0.90, p = 0.01). Radiological re-growth occurred in an average of 26.6% of cases (range 0-54.5%).

CONCLUSION

From our analysis, only the residual tumour volume/size was associated with residual VS growth. Therefore, close postoperative surveillance for the first year, followed by an annual MRI scan for at least 5 years, and subsequently extended interval surveillance remains of utmost importance to monitor disease progression and provide timely surgical and adjuvant interventions. Our study shows that future work should be aimed at molecular and histological characteristics of residual VSs to aid prognostic understanding of growth.

Subtotal Resection of Cervical Dumbbell Schwannomas: Radiographic Predictors for Surgical Considerations

OBJECTIVE

Currently, radiologic predictors for the resectability of cervical dumbbell schwannomas remain unknown. To identify radiologic predictors for resectability, we retrospectively reviewed data from 72 patients.

METHODS

From January 1995 to June 2017, 72 patients who underwent surgical treatment for cervical dumbbell schwannomas were enrolled. We focused on the relationship between preoperative magnetic resonance imaging (MRI) features and the extent of tumor removal. The MRI features evaluated were tumor size, tumor level, Eden classification, degree of vertebral artery (VA) involvement, and signal intensity (SI) on T2-weighted images (WIs).

RESULTS

Among the 72 patients, gross total resection (GTR) and subtotal resection (STR) were achieved in 37 (51.4%) and 35 (48.6%) patients, respectively. Mean maximal tumor size (P = 0.011), mean size of foraminal and extraforaminal portion (P = 0.017), tumor level (P < 0.001), VA involvement (P < 0.001), and SI on T2-WIs (P = 0.006) were significantly different between the GTR and STR groups. Univariate analyses demonstrated that maximal tumor size (odds ratio [OR]: 0.93, P = 0.012), high cervical level (OR: 11.37, P < 0.001), pushed VA (OR: 0.11, P = 0.002), encased VA (OR: 0.02, P < 0.001), and hyper-SI on T2-WIs (OR: 12.46, P = 0.020) were significant predictors for GTR. In the multivariate analysis, only high cervical level (OR: 5.48, P = 0.033) and encased VA (OR: 0.07, P = 0.014) were significant predictors for GTR.

CONCLUSIONS

The resectability of cervical dumbbell schwannomas may be predicted by MRI features, including tumor size, tumor level, and degree of VA involvement.

Stereotactic radiosurgery for recurrent vestibular schwannoma after previous resection

OBJECTIVE

The goal of this retrospective cohort study was to assess long-term outcomes in patients with vestibular schwannoma (VS) who underwent stereotactic radiosurgery (SRS) after initial microsurgical resection.

METHODS

From the authors' database of 1770 patients with VS, the authors retrospectively analyzed data from 173 Gamma Knife SRS procedures for VS after 1 (128 procedures) or multiple (45 procedures) microsurgical resections. The median length of the interval between the last resection and SRS was 42 months (range 2–329 months). The median length of clinical follow-up was 74 months (range 6–285 months). Progression-free survival after SRS was determined with Kaplan-Meier analysis.

RESULTS

At the time of SRS, the hearing of 161 patients (93%) was Gardner-Robertson Class V, and 81 patients (47%) had facial neuropathy (i.e., facial function with House-Brackmann [HB] grades of III–VI), 87 (50%) had trigeminal neuropathy, and 71 (41%) reported imbalance or disequilibrium disorders. The median tumor volume was 2.7 cm3 (range 0.2–21.6 cm3), and the median dose to the tumor margin was 13 Gy (range 11–20 Gy). Radiosurgery controlled growth of 163 (94%) tumors. Progression-free survival after SRS was 97% at 3 years, 95% at 5 years, and 90% at 10 years. Four patients with delayed tumor progression underwent repeat SRS at a median of 35 months (range 23–64 months) after the first SRS. Four patients (2.3%) with tumor progression underwent repeat resection at a median of 25 months (range 19–33 months). Among the patients with any facial dysfunction (indicated by HB grades of II–VI), 19% had improvement in this condition after SRS, and 5.5% with some facial function (indicated by HB grades of I–V) developed more facial weakness. Among patients with trigeminal neuropathy, 20% had improvement in this condition, and 5.8% developed or had worsened trigeminal neuropathy after SRS.

CONCLUSIONS

Stereotactic radiosurgery offered a safe and effective long-term management strategy for VS patients whose tumors remained or recurred after initial microsurgery.

Estimating Tumor Growth Rates In Vivo

In this paper, we develop methods for inferring tumor growth rates from the observation of tumor volumes at two time points. We fit power law, exponential, Gompertz, and Spratt’s generalized logistic model to five data sets. Though the data sets are small and there are biases due to the way the samples were ascertained, there is a clear sign of exponential growth for the breast and liver cancers, and a 2/3’s power law (surface growth) for the two neurological cancers.

Morbidity and mortality following acoustic neuroma excision in the United States: analysis of racial disparities during a decade in the radiosurgery era

Acoustic neuromas present a challenging problem, with the major treatment modalities involving operative excision, stereotactic radiosurgery, observation, and fractionated stereotactic radiotherapy. The morbidity/mortality following excision may differ by patient race. To address this concern, the morbidity of acoustic neuroma excision was assessed on a nationwide level. The Nationwide Inpatient Sample from 1994-2003 was used for analysis. Only patients admitted for acoustic neuroma excision were included (International Classification of Diseases, 9th edition, Clinical Modification = 225.1; primary procedure code = 04.01). Analysis was adjusted for several variables, including patient age, race, sex, primary payer for care, income in ZIP code of residence, surgeon caseload, and hospital caseload. Multivariate analyses revealed that postoperative mortality following acoustic neuroma excision was 0.5%, with adverse discharge disposition of 6.1%. The odds ratio for mortality in African Americans compared with Caucasians was 8.82 (95% confidence interval = 1.85-41.9, P = .006). Patients with high-caseload surgeons (more than 2 excisions/year), private insurance, and younger age had decreased mortality, better discharge disposition, and lower overall morbidity (P < .04). Neither hospital caseload nor median income were predictive factors. African Americans were 9 times more likely to die following surgery than Caucasians over a decade-long analysis. Given the relatively benign natural history of acoustic neuroma and the alarmingly increased mortality rate following surgical excision among older patients, African Americans, and patients receiving care from low-caseload surgeons, acoustic neuromas in these patient populations may be best managed by a more minimally invasive modality such as observation, fractionated stereotactic radiotherapy, or stereotactic radiosurgery.

Residual and recurrent acoustic neuroma in hearing preservation procedures: neuroradiologic and surgical findings

Magnetic resonance imaging with gadolinium DTPA is currently the most accurate method for detecting small intracanalicular yestibular schwannomas. This imaging modality is not nearly as clear in diagnosis of a small residual or recurrent neuroma after a hearing preservation procedure. This study looked for gadolinium-enhanced MRI images mimicking recurrent lesions in 104 consecutive cases of unilateral acoustic neuroma removed with a hearing preservation technique by the retrosigmoid transmeatal approach. A number of cases with enhancing MRI images in the internal anditory canal were reoperated, permitting the histologic examination of the enhancing tissue. Criteria for the MRI diagnosis of residual-recurrent acoustic neuroma are presented, along with the short-to mid-term rate of "residual-recurrent" tumor.

Clinical growth rate of acoustic schwannomas: correlation with the growth fraction as defined by the monoclonal antibody ki-67

The growth rate of acoustic tumors, although slow, varies widely. There may be a continuous spectrum or distinct groups of tumor growth rates. Clinical, audiologic, and conventional histologic tests have failed to shed any light on this problem. Modern immunohistochemical methods may stand a better chance. The Ki-67 monoclonal antibody stains proliferating cells and is used in this study to investigate the growth fraction of 13 skull base schwannomas. The acoustic tumors can be divided into two different growth groups, one with a rate five times the other. The literature is reviewed to see if this differentiation is borne out by the radiologic studies. Distinct growth rates have been reported: one very slow, taking 50 years to reach 1 cm in diameter, a second rate with a diameter increase of 0.2 cm/year, and a third rate five times the second, with a 1.0 cm increase in diameter per year. A fourth group growing at 2.5 cm/year is postulated, but these tumors cannot be followed for long radiologically, since symptoms demand surgical intervention. The clinical implications of these separate growth rates are discussed.

Conservative management of acoustic neuroma

AIM OF STUDY

To identify those patients with vestibular schwannoma (acoustic neuroma) in whom treatment becomes necessary.

METHOD

Retrospective chart review.

RESULT

A total of 205 patients with small tumors were followed for a mean of 40.8 months. The longest follow-up was 180 months. One hundred and ninety-seven patients had a follow-up of more than 12 months. Eight patients with a follow-up of less than 12 months were excluded from the study. In 136 patients (66.3%) the tumor did not grow. Forty-seven patients (23.9%) showed some evidence of slow growth. Eight of 197 patients (4%) had rapid growth and 6 patients (3%) had radiological evidence of tumor regression. Fifteen patients came to surgery. Five of these showed rapid growth, four developed ataxia in whom tumor growth was slow, three had ataxia without tumor growth, two patients developed brainstem compression, and one patient elected to proceed to surgery, although there were no tumor growth or symptoms.

CONCLUSION

Few patients with small tumors will come to surgery in the short term. Perhaps the majority of patients with such small tumors will not need surgery. Long-term follow-up studies of 20 years or more are required to be come more confident about the natural history of these tumors. This study continues.

Natural history of acoustic neuromas

The growth rate of acoustic neuromas was studied in a series of 50 patients who underwent follow-up imaging studies, since surgery was not performed after the initial diagnostic study or only performed after the follow-up studies. In 50% of the cases the tumor did not grow during the length of the follow-up. In the other patients the growth was less than 50% of the original tumor size in all but four. No correlation was observed between tumor growth, length of the follow-up, and age of the patient. Our results suggest a change in the management of this benign tumor.

The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes

Object

Observation is an important consideration when discussing management options for patients with vestibular schwannoma (VS). Most data regarding clinical outcomes after conservative management come from modestsized series performed at individual centers. The authors performed an analysis of the published literature on the natural history of VSs with respect to hearing outcome. Their objective was to provide a comprehensive and unbiased description of outcomes in patients whose disease was managed conservatively.

Methods

The authors identified a total of 34 published studies containing hearing outcome data in patients with VSs < 25 mm in largest diameter who underwent observation management. The effects of initial tumor size and tumor growth rate on hearing function at latest follow-up were analyzed. Data from individual and aggregated cases were extracted from each study. Patients with poorer hearing (American Association of Otolaryngology–Head and Neck Surgery Classes C or D, or Gardner-Robertson Classes III, IV, or V) at the time of presentation were excluded.

Results

A total of 982 patients met the inclusion criteria for this analysis, with a mean initial tumor size of 11.3 ± 0.68 mm. The mean growth rate was 2.9 ± 1.2 mm/year. The length of follow-up for these studies ranged from 26 to 52 months. Patients with preserved hearing at latest follow-up had a statistically larger initial tumor size than those whose hearing declined during the observation period (11.5 ± 2.3 mm vs 9.3 ± 2.7 mm, p < 0.0001), but the 2-mm difference of means was at the limit of imaging resolution and observer reliability. In contrast, patients with lower rates of tumor growth (≤ 2.5 mm/year) had markedly higher rates of hearing preservation (75 vs 32%, p < 0.0001) compared with patients with higher tumor growth rates. Interestingly, the authors' analysis found no difference in the rate of reported intervention for patients in either group (16 vs 18%, p = not significant).

Conclusions

These data suggest that a growth rate of > 2.5 mm/year is a better predictor of hearing loss than the initial tumor size for patients undergoing observation management of VSs < 25 mm in largest diameter.

Spontaneous regression of vestibular schwannomas after resection of contralateral tumor in neurofibromatosis Type 2

The authors report on 2 patients with bilateral vestibular schwannomas (VSs) who underwent unilateral surgical tumor removal. One patient was followed up for 4 years, the other for 9; in both cases, the contralateral VS regressed markedly without any additional treatment during the follow-up period. Serial MR imaging was performed to monitor the untreated tumor, which in both cases involved the only hearing ear. The tumors were assessed volumetrically. The contralateral tumors appeared to enlarge mildly at initial follow-up and then, with no treatment, regressed (to 23% of the original maximum volume in Case 1 and to 15% of the original maximum in Case 2). The largest posterior fossa diameter decreased from 30.1 mm to 18.6 mm in Case 1 over 4 years and from 27 mm to 16 mm over 8 years in Case 2. Hearing declined only mildly during follow-up in both patients.

These cases demonstrate the first well-documented, long-term, spontaneous VS regressions in patients with neurofibromatosis Type 2. They underline the importance of careful observation of VS involving the only hearing ear in the management of bilateral VS to determine the natural growth pattern of the tumors. The mechanism of the dramatic spontaneous tumor regression is uncertain.

Vestibular schwannoma: role of conservative management

Objective:

To assess the outcome of conservative management of vestibular schwannoma.

Study design:

Observational study.

Setting:

Tertiary referral centre.

Patients:

Four hundred and thirty-six patients with vestibular schwannoma (490 tumours), including 327 sporadic tumours and 163 tumours in 109 patients with neurofibromatosis type two.

Main outcome measures:

The relationship of tumour growth to tumour size at presentation, and to certain demographic features.

Results:

The initial tumour size was significantly larger in the neurofibromatosis type two group (11 mm) than in the sporadic vestibular schwannoma group (5.1 mm). In both groups, 68 per cent of tumours did not grow during follow up (mean 3.6 years; range one to 14 years). The mean growth rate was 1.1 mm/year (range 0–15 mm/year) for sporadic tumours and 1.7 mm/year (range 0–18 mm/year) for neurofibromatosis type two tumours. The tumour growth rate correlated positively with tumour size in the sporadic tumour group, and correlated negatively with age in the neurofibromatosis type two group.

Conclusion:

Two-thirds of vestibular schwannomas did not grow. Radiological surveillance is an acceptable approach in carefully selected patients. Once a sporadic vestibular schwannoma reaches 2 cm in intracranial diameter, it is likely to continue growing. We do not recommend conservative management for sporadic tumours with an intracranial diameter of 1.5 cm or more. Vestibular schwannoma management is more complex in patients with neurofibromatosis type two.

Follow-up assessment of vestibular schwannomas: volume quantification versus two-dimensional measurements

Introduction

A conservative treatment strategy is often proposed as a primary treatment option in the management of vestibular schwannomas (VS). In this “wait and scan” policy, audiovestibular symptoms are monitored regularly, and VS growth is measured on consecutive magnetic resonance images (MRI). The aim of this study is validation of two-dimensional versus volume MRI assessment in the longitudinal follow-up of VS and to define tumor growth beyond measurement error.

Methods

MRI scans of 68 consecutive patients with VS were analyzed retrospectively. Two-dimensional and volume measurements on contrast enhanced (CE) T1- and T2-weighted images were performed independently by two readers. Smallest detectable differences (SDD) were calculated, and intraclass correlation coefficients (ICCs) were determined for both assessment methods.

Results

Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images. SDD for differences relative to baseline MRI [SDD (%)] for two-dimensional measurements had a higher interobserver error compared to volume measurements (40% versus 19.7%), which decreases when tumor size increases. The ICC for two-dimensional measurements in three directions was 0.947, 0.974, and 0.978 and for volume measurements 0.999.

Conclusion

Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth. These measurements are assessed preferably on CE T1-weighted images. SDD (%) strongly depends on VS size. SDD between consecutive scans exceeds the common clinical applied criterion of 1 or 2 mm growth to define growth.

Tumor-volume changes after radiosurgery for vestibular schwannoma: implications for follow-up MR imaging protocol

BACKGROUND AND PURPOSE

The outcome of radiosurgery for vestibular schwannoma (VS) is assessed by posttreatment measurement of tumor size and could be influenced by the timing and quality of the assessment. This study evaluates the volumetric changes of VS after radiosurgery and proposes a radiologic follow-up program.

MATERIALS AND METHODS

Of 142 patients with VS treated with radiosurgery, we selected patients who were followed at least 3 times during a minimum of 32 months with a T1-weighted gadolinium-enhanced high-resolution 3D MR imaging examination identical to the pretreatment MR imaging. Forty-five patients were identified with a mean follow-up of 50 months (range, 32-78 months). Pre- and posttreatment tumor volumes were calculated by using BrainSCAN software by manually contouring tumors on each MR imaging study. Volume changes of >13% were defined as events.

RESULTS

At last follow-up MR imaging, volumes were smaller in 37 (82.2%) of the 45 patients. Eleven (29.7%) of these 37 tumors showed transient swelling preceding regression, with a median time to regression of 34 months (range, 20-55 months). Seven (15.6%) of the 45 tumors had volume progression compared with the tumor on pretreatment MR imaging studies. Of these 7 tumors, 3, however, had volume regression compared with the preceding MR imaging study, and in 4, volume progression was ongoing. One tumor remained the same.

CONCLUSIONS

Tumor-volume measurements by standardized T1-weighted gadolinium-enhanced high-resolution 3D MR imaging follow-up protocols revealed good local control of VS after radiosurgery. The first-follow-up MR imaging at 2 years and the second at 5 years postradiosurgery differentiated transient progression from ongoing progression and may prevent unnecessary therapeutic interventions.

The treatment of a large acoustic tumor with fractionated stereotactic radiotherapy

The treatment of acoustic neuromas (AN) usually involves surgical excision or stereotactic radiosurgery. However, for large AN (mean diameter > 3 cm), stereotactic radiosurgery is rarely used, leaving patients with limited noninvasive treatment options. Recently, the use of fractionated stereotactic radiotherapy (FSRT) has been effective in treating small to medium-sized AN. We present a patient with a large AN treated with FSRT. The patient was a 43-year-old man presenting with imbalance, tinnitus, vertigo, and right-sided hearing decline associated with vomiting and hydrocephalus. Magnetic resonance (MR) imaging revealed a large, 3.8-cm, right cerebellopontine-angle tumor compressing the fourth ventricle. Following right frontal ventriculoperitoneal shunt placement, the patient underwent FSRT for treatment of the tumor. Using the Radionics X-Knife 4.0 3D treatment planning system, a total of 54 Gy was delivered in 1.8-Gy daily fractions with the prescription isodose line of 90%. Treatments were delivered using a dedicated Varian 6/100 linear accelerator, and head immobilization was achieved with the Gill-Thomas-Cosman relocatable stereotactic frame. The patient was subsequently evaluated with serial contrast-enhanced MR imaging. Following FSRT, local control (defined as the absence of tumor progression) was achieved, and treatment was well tolerated. There was no hearing-related, trigeminal, or facial-nerve morbidity following FSRT at 63-month follow-up. Treating a patient with a large AN with FSRT resulted in local tumor control, with no trigeminal nerve, facial nerve, or hearing-related morbidity. These results support FSRT as a potential noninvasive treatment modality for AN some would consider too large for single-fraction stereotactic radiosurgery (SRS).

Safety and efficacy of fractionated stereotactic radiotherapy for acoustic neuromas

BACKGROUND

The treatment of acoustic neuromas (AN) has historically involved surgical excision or stereotactic radiosurgery, with a relatively limited number of reports available describing the use of fractionated stereotactic radiotherapy (FSRT). To enhance the existing knowledge regarding the safety and efficacy of this treatment modality, we describe our initial experience with FSRT for AN.

METHODS

From 1999-2005, 20 patients (12F, 8M) with AN underwent FSRT. All patients were treated using the Radionics X-Knife 4.0 3D planning system, receiving 54 Gy in 1.8 Gy daily fractions with a prescription isodose line of 90%. Treatments were delivered stereotactically using a dedicated Varian 6/100 linear accelerator, with immobilization achieved via the Gill-Thomas-Cosman relocatable frame. Median tumor size (maximum diameter) was 2.1 cm (range, 1.1-3.4 cm). Median patient age was 49.5 years, with median follow-up of 22 months (range, 1-66 months). All patients were evaluated with pre- and post-gadolinium-enhanced magnetic resonance imaging.

RESULTS

Following FSRT, local tumor control was achieved in every patient, with the treatment well-tolerated by all patients. No patient experienced acute complications or facial nerve weakness. Two patients experienced permanent trigeminal nerve morbidity manifesting as facial numbness. All nine patients with preserved hearing before treatment had hearing preservation at last follow-up, although four of these patients experienced hearing decline following FSRT.

CONCLUSION

In our series of 20 patients with AN, all had local tumor control following FSRT, with minimal morbidity. These results support the growing body of literature demonstrating the safety and efficacy of FSRT in achieving local control for AN, further validating the viability of FSRT as a treatment modality for this patient population.

Historia magistra vitae (Cic. De or. 2.36). The Prime Objective of Radiosurgery in Acoustic Neurinomas

The central question of stereotaxic radiosurgery in acoustic neurinomas is how to pinpoint its main objective: is it a better alternative to neurosurgery or an option when surgery is unfeasible? This study is a continuation of the article published in 1995 in Acta Neurochirurgica, but benefits from greater experience, more complete analysis and longer supervision of results. The conclusions that can be drawn to date from our own findings and from others in the literature are the following: radiosurgery can be used not only to prevent neurinoma growth and at the same time to preserve the patient's neurological conditions without the risk of complications, but it can also be counted on to provide a cure. However, radiosurgery as an excising device is more insidious than the microsurgical scalpel, since the narrow beam of radiation, directed to a limited target without opening the skull, is invisible. The expression coined by Lars Leksell regarded precisely the innovation he himself conceived in the 'closed skull operation', with reference to its use in cases of acoustic neurinoma as an alternative to traditional surgery. Hence, whatever technique or instruments are involved, it is always a question of interventional neuroradiology or minimally invasive neurosurgery.

Socioeconomic costs of open surgery and gamma knife radiosurgery for benign cranial base tumors

OBJECTIVE

The aim of this study was to evaluate the relative socioeconomic costs of benign cranial base tumors treated with open surgery and gamma knife radiosurgery.

METHODS

In a retrospective study, we studied 174 patients with benign cranial base tumors, less than 3 cm in diameter (or volume less than 30 ml), admitted in the past 5 years. Group A (n = 94) underwent open surgery for removal of the tumors, whereas Group B (n = 80) underwent gamma knife radiosurgery. The socioeconomic costs were evaluated by both direct and indirect cost. The direct costs comprised intensive care unit cost, ward cost, operating room cost, and outpatient visiting cost. The indirect costs included loss of workdays and mortality. The length of hospital stay, the number of lost workdays, surgical complications, mortality, and cost-effectiveness analysis were calculated as well. Student t test and chi test were used for statistical analysis.

RESULTS

The mean length of hospital stay for open surgery was 18.2 +/- 30.4 days including 5.0 +/- 14.7 days of intensive care unit stay and 13.0 +/- 15.2 days of ward stay, P < 0.01. The mean hospital stay for gamma knife was 2.2 +/- 0.9 days with no need of intensive care unit stay, P < 0.01. The mean loss of workdays for open surgery was 160 +/- 158 days and 8.0 +/- 9.0 days for gamma knife, P < 0.01. The gamma knife cost per hour (1435 US dollars) is higher than the open surgery cost per hour (450 US dollars), P < 0.01. The direct cost for gamma knife (9677 US dollars +/- 6700 US dollars) is higher than that for open surgery (5837 US dollars +/- 6587 US dollars), P < 0.01. Open surgery had more complication rates (31.2%) than gamma knife (3.8%). Open surgery had a mortality rate of 5.3%; there was no mortality for gamma knife. The indirect costs, including loss of workdays and mortality, were significantly higher for open surgery than for gamma knife, P < 0.01. Finally, the socioeconomic cost (34,453 US dollars +/- 97,277 US dollars) is higher for open surgery than for gamma knife (10,044 US dollars +/- 7481 US dollars), P < 0.01. The CEA is significantly higher in gamma knife (3762 US dollars/quality-adjusted life year) than in open surgery (8996 US dollars/quality-adjusted life year), P < 0.01.

CONCLUSION

Most of the socioeconomic loss with open surgery for benign cranial base tumors comes from the indirect costs of workdays lost and mortality. Gamma knife radiosurgery is a worthwhile treatment to our patients and to our society because it may shorten hospital stays and workdays lost and reduce complications, mortality, socioeconomic loss, and achieve better cost-effectiveness.

CyberKnife radiosurgery for benign intradural extramedullary spinal tumors

OBJECTIVE

Microsurgical resection of benign intradural extramedullary spinal tumors is generally safe and successful, but patients with neurofibromatosis, recurrent tumors, multiple lesions, or medical problems that place them at higher surgical risk may benefit from alternatives to surgery. In this prospective study, we analyzed our preliminary experience with image-guided radiosurgical ablation of selected benign spinal neoplasms.

METHODS

Since 1999, CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery was used to manage 51 patients (median age, 46 yr; range, 12-86 yr) with 55 benign spinal tumors (30 schwannomas, nine neurofibromas, 16 meningiomas) at Stanford University Medical Center. Total treatment doses ranged from 1600 to 3000 cGy delivered in consecutive daily sessions (1-5) to tumor volumes that varied from 0.136 to 24.6 cm.

RESULTS

Less than 1 year postradiosurgery, three of the 51 patients in this series (one meningioma, one schwannoma, and one neurofibroma) required surgical resection of their tumor because of persistent or worsening symptoms; only one of these lesions was larger radiographically. However, 28 of the 51 patients now have greater than 24 months clinical and radiographic follow-up. After a mean follow-up of 36 months, all of these later lesions were either stable (61%) or smaller (39%). Two patients died from unrelated causes. Radiation-induced myelopathy appeared 8 months postradiosurgery in one patient.

CONCLUSION

Although more patients studied over an even longer follow-up period are needed to determine the long-term efficacy of spinal radiosurgery for benign extra-axial neoplasms, short-term clinical benefits were observed in this prospective analysis. The present study demonstrates that CyberKnife radiosurgical ablation of such tumors is technically feasible and associated with low morbidity.

Size and Growth Rate of Sporadic Vestibular Schwannoma: Predictive Value of Information Available at Presentation

BACKGROUND

The current study examines the hypothesis that tumor growth rate in sporadic vestibular schwannoma could be in part predicted by data available at diagnosis, such as tumor volume, patient age, laterality, and sex.

METHODS

Tumor volumes and growth rates were calculated from serial magnetic resonance imaging data in a cohort of 50 patients (26 men and 24 women; mean age at presentation, 64.1 +/- 12.8 yr). Tumor volumes were measured using an algorithm that corrects for partial volume averaging errors and provides accurate estimates of tumor volume with known errors.

RESULTS

Examination of presentation data showed no relationship between tumor size at diagnosis and patient age, sex, or tumor laterality. Two measurements of tumor growth--absolute growth per annum and tumor volume doubling time--were studied, and neither showed any relationship with tumor size at presentation, patient age, tumor laterality, or sex.

CONCLUSION

The study represents a typical spectrum of patient ages and is of sufficient size in view of the distribution pattern of the variables to give a calculated statistical power in excess of 90% for each variable. This indicates that the clinical features available at presentation and diagnosis have no power to predict the expected behavior of sporadic vestibular schwannoma.

Outpatient gamma knife surgery for vestibular schwannoma: definition of the therapeutic profile based on a 10-year experience

Object. The purpose of the study was to define the therapeutic profile of outpatient gamma knife surgery (GKS) for vestibular schwannoma (VS) by using sequential tumor volumetry to quantify changes following treatment.

Methods. A total of 111 patients met the inclusion criteria. The median follow-up duration was 7 years (range 5–9.6 years). Thirty-seven patients (33%) had undergone surgery before GKS and 10 (9%) had neurofibromatosis Type 2 (NF2). The median VS volume was 1.6 cm3 (range 0.08–8.7 cm3).

The actuarial 6-year tumor control rate after a single GKS treatment was 95%. Tumor swelling was observed in 43 patients (38.7%). Recurrence was significantly associated with NF2 (p < 0.003) and the reduced dose (p < 0.03) delivered to these tumors. The incidence of facial nerve neuropathy was mainly determined by surgery prior to GKS (p < 0.0001). Facial nerve radiation toxicity was mild and transient. No permanent facial nerve toxicity was observed. Trigeminal neuropathy occurred in 13 patients, and this was correlated with the VS volume (p < 0.02). The median hearing loss was −10 dB (range + 20 dB to −70 dB). The risk of hearing loss was correlated with age and transient tumor swelling (p < 0.05) but not with dose parameters or NF2.

Conclusions. Outpatient GKS is feasible, effective, and safe. Its therapeutic profile compares favorably with that of microsurgery.

Outpatient gamma knife surgery for vestibular schwannoma: definition of the therapeutic profile based on a 10-year experience

Object.The purpose of the study was to define the therapeutic profile of outpatient gamma knife surgery (GKS) for vestibular schwannoma (VS) by using sequential tumor volumetry to quantify changes following treatment.

Methods.A total of 111 patients met the inclusion criteria. The median follow-up duration was 7 years (range 5–9.6 years). Thirty-seven patients (33%) had undergone surgery before GKS and 10 (9%) had neurofibromatosis Type 2 (NF2). The median VS volume was 1.6 cm3(range 0.08–8.7 cm3).

The actuarial 6-year tumor control rate after a single GKS treatment was 95%. Tumor swelling was observed in 43 patients (38.7%). Recurrence was significantly associated with NF2 (p < 0.003) and the reduced dose (p < 0.03) delivered to these tumors. The incidence of facial nerve neuropathy was mainly determined by surgery prior to GKS (p < 0.0001). Facial nerve radiation toxicity was mild and transient. No permanent facial nerve toxicity was observed. Trigeminal neuropathy occurred in 13 patients, and this was correlated with the VS volume (p < 0.02). The median hearing loss was −10 dB (range + 20 dB to −70 dB). The risk of hearing loss was correlated with age and transient tumor swelling (p < 0.05) but not with dose parameters or NF2.

Conclusions.Outpatient GKS is feasible, effective, and safe. Its therapeutic profile compares favorably with that of microsurgery.

Is clinical growth index a reliable predictor of tumour growth in vestibular schwannomas?

We have assessed the clinical growth index as an indicator of tumour growth rate in 50 patients with a vestibular schwannoma. Clinical growth index was calculated by measuring the length of history and dividing it by the maximum tumour diameter. Total tumour volumes were also measured from all MRI examinations and an effective tumour volume doubling time was calculated. Radiological growth measurements demonstrated involution in 10/50 patients. The median volume doubling time was 1.65 years (range 20.9-46.3 months, skewness 1.72 years). The median clinical growth index was 0.030 cm per month (range 0-0.270 cm per month, skewness 2.398). There was no significant correlation between volume doubling time and clinical growth index. Identification of rapidly growing tumours with clinical growth index >0.025 cm/month had a positive predictive value of 61%, negative predictive value of 48%, false-positive rate of 30% and false-negative rate of 52%. In conclusion, we have shown that the growth rate of vestibular schwannoma is not related to the clinical growth index and we recommend that this measure should be abandoned in the clinical management of patients where conservative management regimes are being considered.

Relative indications for radiosurgery and microsurgery for acoustic schwannoma

The physical and biological principles underlying the use of radiosurgery for the treatment of vestibular schwannomas of up to 2.5 cm in diameter are reviewed together with the historical controversies that have surrounded its introduction. The results in terms of mortality, quality of life, preservation of facial movement and hearing, incidence of shunt-dependent hydrocephalus, cancer neogenesis and brain stem damage are compared in the Marseilles series of 600 microsurgical procedures and 830 Gamma knife procedures and with the peer-reviewed literature. The key principles of a steep profile to radiation exposure at the tumour margin, careful topographical planning of the radiation against the tumour shape to minimise the radiation dose to the cranial nerves and brain stem, early tumour swelling, tumour texture and national history of the tumour are analysed. Protocols for the management of unilateral schwannoma, Type II neurofibromatosis (both the Wishart and the Gardner types) and residual/recurrent tumours are presented. In summary, the growth of nearly 97% of vestibular schwannomas (up to 2.5 cm) is arrested by the Gamma knife, the facial nerve is preserved in almost all cases and hearing may be preserved at its pre-operative level in nearly 70% of cases without the complications of microsurgery.

Stereotactic radiosurgery of acoustic tumors

Stereotactic radiotherapy has an inherent disadvantage in that it does not directly reduce tumor volume. In this increasing environment of cost-containment, however, this modality offers several advantages (see box). Some investigators believe that, over the next generation, stereotactic radiotherapy will be the mainstay of vestibular schwannoma care, with microsurgery being the exception and being reserved for patients needing urgent decompression and for very young patients [12]. Increasing numbers of patients are undergoing stereotactic radiotherapy as a matter of preference following the provision of sufficient information on the two treatment procedures. When counseling younger patients, it is important to remember that no long-term data about the control rate for stereotactic radiotherapy with the most recent, lower doses are available. Also, surgical salvage, which is necessary in some patients, produces a poor outcome following radiation therapy. Published reports have demonstrated similar facial nerve, hearing preservation, and tumor control rates in the short term only [32,33]. Data is insufficient to assess the risk for inducing a secondary, treatment-related malignancy. Until long-term results are available, stereotactic radiotherapy should be reserved for medically infirm patients, elderly patients, patients with contralateral deafness or bilateral tumors, and patients who have failed prior microsurgery. Radiotherapy is not the preferred primary treatment modality for vestibular schwannoma based on currently published results.

Vestibular schwannoma growth in patients with neurofibromatosis Type 2: a longitudinal study

OBJECT

The factors that determine the growth rates of vestibular schwannomas (VSs) in patients with neurofibromatosis Type 2 (NF2) are unknown. The authors undertook this study to determine if clinical factors or type of constitutional NF2 mutation were associated with VS growth rates in cases of NF2.

METHODS

The authors reviewed serial gadolinium-enhanced magnetic resonance (MR) images of the head and full spine of 37 patients with sporadic NF2 who had been observed over periods ranging from 0.2 to 8 years (median 3.9 years) at a specialized referral clinic for NF2. A box model was used to calculate VS volumes so that tumor growth rates could be estimated. Temperature-gradient gel electrophoresis was used to screen for constitutional NF2 mutations. The VS growth rates tended to decrease with increasing patient age at onset of signs or symptoms (r2 = 0.23, p = 0.003) and at the time the baseline gadolinium-enhanced MR image was obtained (r2 = 0.38, p < 0.001). The authors did not find significant associations between VS growth rates and the number of non-VS cerebral or spinal tumors or different types of constitutional NF2 mutations.

CONCLUSIONS

There is considerable variability in growth rates of VSs in patients with NF2, but they tend to be higher in patients who are younger at onset of signs or symptoms.

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.

Reduced-dose radiosurgery for vestibular schwannomas

OBJECTIVE

To evaluate tumor control and complications associated with low-dose radiosurgery for vestibular schwannomas.

METHODS

Between December 1993 and January 2000, 47 patients with vestibular schwannomas were treated at our center with gamma knife radiosurgery. The marginal tumor doses ranged from 7.5 to 14.0 Gy (median, 12.0 Gy) for patients treated after microsurgery and from 10.0 to 15.0 Gy (median, 12.0 Gy) for patients in whom radiosurgery was the primary treatment. The median maximum tumor diameter was 18 mm (range, 3-50 mm). Evaluation included audiometry, neurological examination, and serial imaging tests. A survey was conducted at the time of analysis.

RESULTS

Follow-up data were available for 45 patients and ranged from 1 to 7 years (median, 3.6 yr). In 43 patients (96%), tumor control (no radiographic progression or surgical resection) was observed. All 33 previously untreated patients had tumor control. Transient facial weakness, experienced in two patients (4%), had resolved completely within 6 months. No patient developed trigeminal neuropathy. Hearing was diminished from baseline in 12% of patients with useful hearing (Gardner-Robertson Class III). However, all patients with pretreatment hearing Gardner-Robertson Class I or II maintained testable hearing (Class I to III) at the most recent examination.

CONCLUSION

Low-dose radiosurgery in this series provided comparable local control and decreased incidences of complications in relation to other reports. Additional follow-up will allow more definitive conclusions to be reached regarding the ultimate rates of tumor control and hearing preservation. Nevertheless, the current dose used for vestibular schwannomas at the University of Maryland Medical Center is 12.0 Gy to the tumor periphery.

Update on conservative management of acoustic neuroma

OBJECTIVE

To update the authors' experience with conservative management of acoustic neuromas.

STUDY DESIGN

Retrospective chart review.

SETTING

Private practice and tertiary care referral setting.

INTERVENTION

Of 600 patients with acoustic neuroma, 102 were treated with the "wait and scan" treatment option. At least two magnetic resonance imaging scans were required of all patients.

MAIN OUTCOME MEASURES

Change in tumor size over time was evaluated, as were clinical symptoms: hearing status, tinnitus, balance disturbance, aural fullness, vertigo, headache, and facial pain, numbness, or weakness.

RESULTS

Of 102 patients, the average follow-up time interval was 28.5 months. Forty-five (44%) of 102 patients demonstrated a change in tumor size: an average total growth of 2.17 mm per year. In the remaining 54 patients (53%), no growth was demonstrated during a mean follow-up of 28.5 months. Three patients demonstrated actual tumor shrinkage. Of the 102 patients receiving conservative treatment, 85 (84%) reported hearing loss, 67 (66%) tinnitus, 37 (36%) balance disturbance, 29 (28%) aural fullness, 28 (27%) vertigo, 7 (7%) headache, 4 (4%) facial numbness, 2 (2%) facial weakness, and 0 (0%) facial pain.

CONCLUSION

Conservative management-"wait and scan"-for selected patients with acoustic neuroma is a reasonable choice of management instead of radiation or microsurgery. In some situations the individual morbidities associated with surgery or radiation make those treatments not in the patient's best interests. A third option is necessary in patients who cannot or do not wish to undergo those other treatments.

Hearing loss and growth rate of acoustic neuromas in follow-up observation policy

OBJECTIVE

It is important to know the growth rate of acoustic neuroma in setting up its observation policy. One aimed to evaluate the significance of growth rate and hearing loss speed from a retrospective study of 31 patients.

METHODS

Thirty-one patients with acoustic neuroma (mean age, 57.1 years; range, 9-81 years) who had undergone MRI and audiometry were retrospectively examined. Changes in tumor size and hearing level during follow-up periods were analyzed.

RESULTS

The mean annual growth rate was 2.4 mm/year (maximum, 17 mm/year), and the average annual hearing loss speed was 2.3 dB/year (-15.0 - 19.2 dB/year) in the follow-up, and a correlation was recognized between them. Whereas significant difference was noted in annual growth rate and hearing loss speed between the sexes, no correlation was recognized between the annual growth rate or hearing loss speed and the age, tumor size and pure tone average (PTA) at the initial diagnosis.

CONCLUSION

Attention must be paid to the acoustic neuroma cases where tumor growth rate is markedly high and those where hearing level rapidly declines during follow-ups. It is difficult, however, to estimate tumor diameter in relation with the changes in hearing level because the natural course of an acoustic neuroma varies in each individual.

Assessment of vestibular schwannoma growth: application of a new measuring protocol to the results of a longitudinal study

This study pertains to a group of 44 patients with unilateral vestibular schwannoma who did not undergo surgery. Prospectively, the dimensions of the tumor were depicted at regular intervals by means of magnetic resonance imaging and then judged independently by an otolaryngologist and a neuroradiologist. Retrospectively, the size of the tumor was quantified by measuring the maximum surface of the lesion in the axial plane. The retrospective surface measurements confirmed the assessments made in the prospective part of the study: growth in 18% of the patients and shrinkage in 7%; 75% remained unchanged. This approach is a pragmatic means to determine whether the size of a tumor has changed over the course of time.

Tumor volume measurements of acoustic neuromas with three-dimensional constructive interference in steady state and conventional spin-echo MR imaging

The purpose was to compare three-dimensional (3D) constructive interference in steady state (CISS) and conventional spin-echo (SE) MR imaging in tumor volume measurements of acoustic neuromas. Twenty-two patients with acoustic neuromas were examined using high-resolution 3D-CISS and SE imaging at a 1.5-T system. Tumor volume determined by SE imaging with the ellipsoid formula was overestimated by 692 mm(3)(35%) on average as compared with that at 3D-CISS with the voxel-count method (the reference standard). Intra- and interobserver variations in SE imaging were poor as compared with 3D-CISS imaging. However, tumor volume results with SE imaging showed a high correlation with those using 3D-CISS imaging (P <. 0001). On the basis of diameters shown on SE images, the tumor volume could be assessed using the following equation (P <.0001): (Tumor volume) = -26.407 + 0.387 x (maximum diameter along the pyramid) x(maximum diameter perpendicular to the pyramid) x (maximum height). J. Magn. Reson. Imaging 2000;12:826-832.

Vestibular schwannoma growth: the continuing controversy

OBJECTIVE

To investigate the growth of vestibular schwannoma (VS) in a series of 123 patients with 127 tumors allocated to the "wait and scan" group in the period 1973-1999.

STUDY DESIGN

Retrospective review of prospectively registered data on all patients with VSIE from the entire country who were allocated to the wait and scan group.

METHOD

Clinical charts, audiometric data, and neuroradiological images were reviewed and tabulated for age, hearing level expressed as speech reception threshold (SRT) and speech discrimination score (SDS), maximum extra-canalicular tumor extension, and possible changes in tumor diameter. The material was updated three times (in June 1993, June 1996, and June 1999). Via the Danish national register, data on whether the included patients were alive or dead were collected in 1999.

RESULTS

The tumor growth, growth rate, and growth patterns were calculated in three periods 1973 to 1993 (mean observation period, 3.4 y), 1973 to 1996 (mean observation period, 3.8 y), and from 1973 to 1999 (mean observation period, 4.2 y). By termination of the first period, 94 tumors (74%) exhibited measurable growth, 23 tumors (18%) no measurable growth, and 10 tumors (8%) revealed negative growth. By the end of the extended observation period, tumor growth was observed in 104 tumors (82%), no tumor growth in 15 tumors (12%), and negative growth in 8 tumors (6%). Subsequent to the third observation period, growth was observed in 108 tumors (85%), no growth in 11 tumors (9%) and negative growth in 8 tumors (6%). However, the results may also be interpreted in another way: 52 patients (42%) were alive at the time of writing, tumor growth did not demand any intervention, 23 patients (19%) died as a result of non-tumor-related causes, and 35 patients (28%) were previously treated and alive by the termination of the third observation period.

CONCLUSION

Depending on the observation period, three sets of growth results were obtained. The long observation period, updating and re-updating the results, gave us the opportunity for a de novo interpretation of the results and the long-term consequences of the wait and scan policy. Combined with other factors, the achieved results should be considered when timing of surgery is to be decided.

Results of linear accelerator-based stereotactic radiosurgery for recurrent and newly diagnosed acoustic neuromas

Stereotactic radiosurgery (SRS) is used to treat acoustic neuromas, but additional information is needed to firmly establish its safety and efficacy. We review our experience over 7 years treating 29 consecutive patients with a modified linear accelerator (linac) SRS system. Between August 1989 and October 1995, 29 patients with a median age of 67 years (range 26 to 83) underwent linac SRS treatment. Twenty-five patients had unilateral acoustic neuromas, and four patients with neurofibromatosis type II had bilateral vestibular schwannoma. Eligibility criteria for SRS were recurrent tumors (n = 9), age >65 (n = 16), or patient preference (n = 6). Follow-up magnetic resonance imaging scans were performed on all patients. The most common presenting symptoms were hearing impairment (18 patients) and gait difficulties (17 patients). Ten patients were deaf in the affected ear prior to treatment. Doses to the periphery of the tumor ranged from 800 to 2,400 cGy (median 1, 600 cGy) prescribed to the 50% to 80% isodose line (median 80%). After a median radiographic follow-up of 49 months (range 4 to 110 months), 11 tumors were smaller, 17 were stable, and one had evidence of progression (at 41 months). The 5-year local disease control rate (Kaplan-Meier estimate) was 94%. Acute complications were minimal, with only two patients experiencing nausea and vomiting after the procedure. Long-term complications included new or progressive trigeminal and facial nerve deficits with estimated 5-year incidences of 15% and 32%, respectively. Subjective hearing reduction or loss occurred in 14 (74%) of the 19 patients who had useful hearing prior to treatment. Five patients died from unrelated causes. These results suggest that linac SRS provides excellent short-term tumor control rates. Since there was a high risk of cranial nerve neuropathy, we do not recommend using only computed tomography-based planning and high prescription doses. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 145-151 (2000).

The role of conservative management of vestibular schwannomas

Although microsurgery is generally regarded as the conventional treatment of choice for most vestibular schwannomas, there remains a group of patients in whom a conservative management approach may be a desirable alternative. The aim of this study was to determine the natural history and outcome following the conservative management of 72 patients with unilateral vestibular schwannomas. The reasons for conservative management included poor general health, age, patient preference, small tumour size, minimal or no symptoms, and tumour in the only/better hearing ear. The mean duration of follow-up was 39.8 months (range 12-194 months). All patients underwent serial magnetic resonance imaging (MRI) for assessment of tumour growth. Patients were deemed to have failed conservative management if there was evidence of continuous or rapid radiological tumour growth and/or increasing symptoms or signs. The mean tumour growth rate, according to the 1995 guidelines of the American Academy of Otolaryngology/Head and Neck Surgery, was 1.16 mm/year (range: 0.75 9.65 mm/year). Approximately 83% of tumours grew at < 2 mm/year. Significant tumour growth was seen in 36.4%, no or insignificant growth in 50%, and negative growth in 13.6% of tumours. The growth rate of CPA tumours (1.4 mm/year) was significantly greater than that of IAC tumours (0.2 mm/year) (P = 0.001). Failure of conservative management, in which active treatment was required, occurred in 15.3%. The outcome of these patients appeared to be as favourable to a comparable group who underwent primary treatment, without a period of conservative management. The mean growth rate of tumours in patients who failed conservative management (4.2 mm/year) was significantly greater than that in patients who did not fail (0.5 mm/year) (P < 0.01). No factors predictive of tumour growth or failure of conservative management were identified. Deterioration of mean pure tone average (0.5, 1, 2, 3 kHz) and speech discrimination scores occurred regardless of whether radiological tumour growth was demonstrated or not. This study suggests that in a select number of cases of vestibular schwannoma, a conservative management approach may be appropriate. Regular follow-up with serial MRI is mandatory. Deterioration of auditory function occurs even in the absence of tumour growth.

Consequences to hearing during the conservative management of vestibular schwannomas

OBJECTIVE

To estimate the risk of loss of serviceable hearing during the conservative management of vestibular schwannomas.

STUDY DESIGN

Retrospective case review.

METHODS

Twenty-five patients with a radiological diagnosis of unilateral vestibular schwannoma were managed conservatively for a mean duration of 43.8 months (range, 12-194 mo). The pure-tone average (PTA) (0.5, 1, 2, and 3 kHz) and speech discrimination scores (SDS) were measured at regular intervals throughout the entire duration of follow-up. Serviceable hearing was defined using two criteria: 70% SDS/30 dB PTA (the 70/30 rule) and 50% SDS/50 dB PTA (the 50/50 rule). The size and growth rate of tumors were determined according to the American Academy of Otolaryngology-Head and Neck Surgery guidelines (1995). Intervention was recommended if there was evidence of continuous or rapid radiological tumor growth, and/or increasing symptoms or signs suggestive of tumor growth.

RESULTS

The risk of loss of serviceable hearing for the total group was 43% using the 70/30 rule and 42% using the 50/50 rule. Tumor growth was considered significant (> 1 mm) in 8 tumors (32%) and nonsignificant in 17 (68%). The risk of loss of serviceable hearing for the tumor-growth group was 67% using the 70/30 rule and 80% using the 50/50 rule. In contrast, the risk of loss of serviceable hearing for the no tumor-growth group was 25% using the 70/30 rule and 14% using the 50/50 rule. No audiological factors predictive of tumor growth were identified.

CONCLUSIONS

There is a significant risk of loss of serviceable hearing during the conservative management of vestibular schwannomas. This risk appears to be greater in tumors that demonstrate significant growth.

Vestibular schwannoma management. Part I. Failed microsurgery and the role of delayed stereotactic radiosurgery

OBJECT

The purpose of this study was to analyze patient outcomes and to define the role of radiosurgery in patients who have undergone prior microsurgical resection of their vestibular schwannoma.

METHODS

The authors evaluated the pre- and postoperative clinical and neuroimaging characteristics of 76 consecutive patients with 78 vestibular schwannomas who underwent radiosurgery after previous surgical resection. Twenty-nine patients (37% of tumors) had undergone more than one prior resection. Forty-three patients (55% of tumors) had significant impairment of facial nerve function (House-Brackmann Grades III-VI) after their microsurgical procedure; 50% had trigeminal sensory loss, and 96% had poor speech discrimination (< 50%). The median evaluation period following radiosurgery was 43 months (range 12-101 months). Tumor growth control after radiosurgery was achieved in 73 tumors (94%). Six patients underwent additional surgical resection despite radiosurgery (median of 32 months after radiosurgery), and one patient underwent repeated radiosurgery for tumor progression outside the irradiated volume. Eleven (23%) of 47 patients with Grades I to III facial function before radiosurgery developed increased facial weakness after radiosurgery. Eleven patients (14%) developed new trigeminal symptoms.

CONCLUSIONS

Radiosurgery proved to be a safe and effective alternative to additional microsurgery in patients in whom the initial microsurgical removal failed. Stereotactic radiosurgery should be considered for all patients who have regrowth or progression of previously surgically treated vestibular schwannomas.

Vestibular schwannoma management in the next century: a radiosurgical perspective

PURPOSE

To discuss how the evolution of vestibular schwannoma radiosurgery, changes in health care delivery, and patient accessibility to medical information will affect the management of vestibular schwannomas in the future.

CONCEPT

In comparison with microsurgical resection of vestibular schwannomas, radiosurgery has a lower morbidity rate, a similar risk of requiring further surgery, and higher patient satisfaction. As this information becomes more widely available to patients and third-party payors, radiosurgery may replace surgical resection as the preferred management strategy for patients with small to medium sized vestibular schwannomas in the United States.

RATIONALE

It is estimated that 2500 patients are diagnosed with vestibular schwannomas each year in the United States. Assuming that 80% undergo surgery, 2000 operations are performed annually for newly diagnosed vestibular schwannomas. Data available since 1987 regarding the number of cases for which gamma knife radiosurgery was performed were used to predict the number of patients who will undergo vestibular schwannoma radiosurgery in the future. If the current trend continues, an equal number of patients will undergo surgical resection and radiosurgery to treat their vestibular schwannomas (approximately 1000/yr) sometime between 2005 and 2010. Moreover, it is predicted that by 2020, two-thirds of the patients who are newly diagnosed with vestibular schwannomas will undergo radiosurgery, with surgical resection being reserved for patients with large tumors associated with symptomatic brain stem compression.

DISCUSSION

Early data regarding vestibular schwannoma radiosurgery predicted an exponential growth curve. Although it is premature to assume that the current trend will continue, it is likely that an ever increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data are published regarding long-term tumor growth control rates. If the mathematical model proves to be accurate, then stereotactic radiosurgery will replace surgical resection as the preferred management strategy for the majority of patients with vestibular schwannomas.

Neurofibromatosis type 2: growth stimulation of mixed acoustic schwannoma by concurrent adjacent meningioma: possible role of growth factors. Case report

The authors report the case of a young man suffering from neurofibromatosis type 2 (NF2) who harbored bilateral acoustic schwannomas and a parasellar meningioma. Neuroimaging studies performed during a 4-year follow-up period showed that the bilateral schwannomas had grown very little and at similar rates. However, after the meningioma had infiltrated the tentorium and approached the ipsilateral schwannoma at the incisura, both Schwann cell tumors started to grow rapidly, particularly the one adjacent to the meningioma, of which the percentage of annual growth rate increased by approximately a factor of 10(2). At the same time, magnetic resonance imaging showed that this tumor also changed its features. During surgery, the acoustic schwannoma was firmly adherent to both meningioma and tentorium. Histological examination revealed meningotheliomatous cells in the schwannoma adjacent to the meningioma. Antiphosphotyrosine immunoblotting of PC12 cells was compatible with the presence of an epidermal growth factor (EGF)-like molecule in the cerebrospinal fluid (CSF) of the patient. This factor was not detected in the CSF of five other NF2 patients, two of whom bore associated bilateral acoustic schwannomas and meningioma in remote locations. It is hypothesized that the meningotheliomatous cells infiltrating the schwannoma triggered an autocrine/paracrine growth-stimulatory mechanism that involved an EGF-like factor.

Acoustic neuroma/vestibular schwannoma growth: past, present and future

The growth of vestibular schwannoma (VS) was investigated in a series of 123 patients with 127 tumors in the period 1973 1993. The material was reanalysed and updated 3 years later in 1996. By termination of the first observation period (mean 3.4 years), 94 tumors (74%) exhibited measurable growth, 23 tumors (18%) no measurable growth and 10 tumors (8%) negative growth. By the end of the extended observation period (mean 3.8 years), tumor growth was observed in 104 tumors (82%), no tumor growth in 15 tumors (12%) and negative growth in eight tumors (6%). Several growth patterns were noticed: however, these were not static as the growth patterns of the tumors changed during the extended observation period. Accordingly, the expected growth figures by the end of this century (mean observation period approximately 4 years) will probably be: growth in 111 tumors (87%), no growth in 10 tumors (8%) and negative growth in six tumors (5%). The results indicate that neither the present study nor the previously published studies on tumor growth reflect the natural history of VS, but they only provide information on tumor growth, growth rates and growth patterns during a given observation period.

Neurofibromatosis type 2: growth stimulation of mixed acoustic schwannoma by concurrent adjacent meningioma: possible role of growth factors

The authors report the case of a young man suffering from neurofibromatosis type 2 (NF2) who harbored bilateral acoustic schwannomas and a parasellar meningioma. Neuroimaging studies performed during a 4-year follow-up period showed that the bilateral schwannomas had grown very little and at similar rates. However, after the meningioma had infiltrated the tentorium and approached the ipsilateral schwannoma at the incisura, both Schwann cell tumors started to grow rapidly, particularly the one adjacent to the meningioma, of which the percentage of annual growth rate increased by approximately a factor of 102. At the same time, magnetic resonance imaging showed that this tumor also changed its features. During surgery, the acoustic schwannoma was firmly adherent to both meningioma and tentorium. Histological examination revealed meningotheliomatous cells in the schwannoma adjacent to the meningioma. Antiphosphotyrosine immunoblotting of PC12 cells was compatible with the presence of an epidermal growth factor (EGF)-like molecule in the cerebrospinal fluid (CSF) of the patient. This factor was not detected in the CSF of five other NF2 patients, two of whom bore associated bilateral acoustic schwannomas and meningioma in remote locations. It is hypothesized that the meningotheliomatous cells infiltrating the schwannoma triggered an autocrine/paracrine growth-stimulatory mechanism that involved an EGF-like factor.

Does surgical removal of primary melanoma trigger growth of occult metastases? An analytical epidemiological approach

BACKGROUND

In several human tumor systems a potential role of surgical removal of the primary tumor upon metastatic tumor growth has been evaluated, as it has been in experimental models. The present study addresses the question of whether the removal of primary melanomas disinhibits growth of metastatic disease and results in more rapid progression.

METHODS

In a data set of 1224 primary cutaneous melanomas the risk of "thin" melanomas to develop metastases within 1 year was compared with the risk of matched pairs of "thick" melanomas to present metastases at the time of diagnosis. For this purpose, a pairwise matching procedure based on certain assumptions as to tumor volume and tumor doubling time has been applied.

RESULTS

When a long tumor doubling time is assumed (200, 400, or 800 days), the tumors removed seem to have a significantly higher risk of metastases to become clinically apparent within 1 year than the matched pairs of tumors to present metastatic disease at the time of diagnosis (chi-square < 0.01). When short tumor doubling time is assumed (50 or 100 days), the difference is not significant, but there also seems to be no benefit for the operated patients.

CONCLUSION

In the present data set there is evidence that surgery of primary melanoma may enhance tumor growth at metastatic sites.