Long-term outcomes after radiosurgery for acoustic neuromas

Twenty years' experience in the treatment of acoustic neuromas with fractionated radiotherapy: a review of 45 cases

PURPOSE

To evaluate very long-term results of fractionated radiotherapy (FRT) of acoustic neuromas (AN).

METHODS AND MATERIALS

From January 1986 to January 2004, FRT was performed in 45 consecutive patients (46 AN). Indications were as follows: poor general condition contraindicating surgery, hearing preservation in bilateral neuromas, partial resection, nonsurgical recurrence. A 3-field to 5-field technique with static beams was used. A mean total dose of 51 Gy was given (1.80 Gy/fraction). The median tumor diameter was 31 mm (range, 11-55 mm). The median follow-up from FRT was 80 months (range, 4-227 months).

RESULTS

The particularity of our series consists of a very long-term follow-up of FRT given to selected patients. Nineteen patients died, two with progressive disease, and 17 from non-AN causes. A serviceable level of hearing was preserved in 7/9 hearing patients. No patient had facial or trigeminal neuropathy. Tumor shrinkage was observed in 27 (59%) and stable disease in 16 (35%). Tumor progression occurred in three patients, 12 to 15 months after FRT. Two additional tumors recurred after shrinkage 20 and 216 months after treatment and were operated on. Actuarial local tumor control rates at 5 and 15 years were 86%. For the patient who had a tumor recurrence at 216 months, histologic examination documented transformation to a low-grade malignant peripheral nerve sheath tumor.

CONCLUSION

Very long-term efficacy of FRT is well documented in this series. However, our results suggest that malignant transformation can occur many years after FRT so we advocate caution when using this treatment for young patients.

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.

Patient Outcomes After Vestibular Schwannoma Management: a Prospective Comparison of Microsurgical Resection and Stereotactic Radiosurgery

OBJECTIVE

The best management for patients with small- to medium-sized vestibular schwannomas (VS) is controversial.

METHODS

: A prospective cohort study of 82 patients with unilateral, unoperated VS less than 3 cm undergoing surgical resection (n = 36) or radiosurgery (n = 46). Patients undergoing resection were younger (48.2 yr versus 53.9 yr, P = 0.03). The groups were similar with regard to hearing loss, associated symptoms, and tumor size. The mean follow-up period was 42 months (range, 12-62 mo).

RESULTS

Normal facial movement and preservation of serviceable hearing was more frequent in the radiosurgical group at 3 months (P < 0.001), 1 year (P < 0.001), and at the last follow-up examination (P < 0.01) compared with the surgical resection group. Patients undergoing surgical resection had a significant decline in the following subscales of the Health Status Questionnaire 3 months after surgery: physical functioning (P = 0.006), role-physical (P < 0.001), energy/fatigue (P = 0.02), and overall physical component (P = 0.004). Patients in the surgical resection group continued to have a significant decline in the physical functioning (P = 0.04) and bodily pain (P = 0.04) subscales at 1 year and in bodily pain (P = 0.02) at the last follow-up examination. The radiosurgical group had no decline on any component of the Health Status Questionnaire after the procedure. The radiosurgical group had lower mean Dizziness Handicap Inventory scores (16.5 versus 8.4, P = 0.02) at the last follow-up examination. There was no difference in tumor control (100 versus 96%, P = 0.50).

CONCLUSION

Early outcomes were better for VS patients undergoing stereotactic radiosurgery compared with surgical resection (Level 2 evidence). Unless long-term follow-up evaluation shows frequent tumor progression at currently used radiation doses, radiosurgery should be considered the best management strategy for the majority of VS patients.

Diagnosis and treatment options for nerve sheath tumors

The purpose of this review is to discuss the contemporary diagnosis and treatment options for nerve sheath tumors. Common nerve sheath tumors include schwannomas, neurofibromas and malignant nerve sheath tumors. Nerve sheath tumors can be associated with genetic disorders such as neurofibromatosis and schwannomatosis. There is great variation in terms of tumor location, clinical presentation and treatment strategy. Magnetic resonance imaging is the diagnostic study of choice for nerve sheath tumors and surgery has become the mainstay of treatment for most symptomatic lesions. Progress in microsurgical techniques has resulted in significant improvement in surgical outcome, with preservation of neurologic function. Complete resection of benign nerve sheath tumors is the goal of surgical intervention and this results in cure. In contrast, malignant nerve sheath tumors remain a major challenge with poor outcomes overall. Progress in multidisciplinary research may ultimately lead to novel therapeutic strategies.

Evaluation of Tumor Expansion after Stereotactic Radiosurgery in Patients Harboring Vestibular Schwannomas

OBJECTIVE:

Stereotactic radiosurgery has been accepted as a safe and effective treatment in patients harboring a vestibular schwannoma. However, during follow-up, tumor expansion induced by high-dose irradiation can occur. Tumor expansion is more likely to be transient, but this phenomenon causes some confusion regarding whether further treatment should be performed. Our purpose was to clarify what type of tumor expansion requires additional treatment.

METHODS:

Between May 1991 and December 1998, 346 patients with a vestibular schwannoma, excluding two with neurofibromatosis, were treated using gamma knife radiosurgery. Of these, serial follow-up images to evaluate tumor expansion were available for 254 patients. Tumor expansion was classified into three types: central necrosis (Type A), solid expansion (Type B), and cyst enlargement or formation (Type C).

RESULTS:

Forty-two patients (17%) had tumor expansion during follow-up. Seventeen patients required additional treatment and 25 did not have any treatments after gamma knife radiosurgery. Type A, B, and C expansion was found in 14, 16, and 12 patients, respectively. Of these, three Type A patients, seven Type B patients, and seven Type C patients underwent salvage treatments. All patients in whom cyst formation developed eventually required craniotomy.

CONCLUSION:

Although tumor expansion was more likely to be transient, additional treatments should be considered in patients who experience neurological deterioration. We strongly recommend simply waiting and obtaining frequent follow-up images until the patients experience neurological deterioration, even when tumor expansion is developing, excluding cyst formation, which tends to continue.

Vestibular schwannoma management: What is the 'best' option?

There is an abundance of medical literature describing the management options for vestibular schwannomas. However, the lack of high quality clinical trials means that, for any individual patient, the decision is often based on the clinician's personal biases. The management options that are available are conservative treatment, surgery, single-dose stereotactic radiosurgery and fractionated radiotherapy. In this review, we set out what the aims of managing a vestibular schwannoma should be and compare how these different treatment modalities perform. The particular objectives of tumour control, cranial nerve preservation, prevention of malignancy, quality of life and cost-effectiveness are discussed. It remains difficult to differentiate between these methods when more than one is suitable; the literature confirms that they are all safe and effective, but the decision must be the patient's, based on their individual priorities. This review should equip the clinician to provide an informed overview of the options.

Facial nerve function after excision of large acoustic neuromas via the suboccipital retrosigmoid approach

We review our results for facial nerve preservation in 105 patients with large acoustic neuromas (diameter 4.0 cm or larger) undergoing excision via the suboccipital retrosigmoid approach. Microneurosurgical techniques and facial nerve monitoring were used. Complete tumor removal was achieved in 91 cases (86.7%) and subtotal removal in 14 (13.3%). There were two postoperative deaths (1.9%). The facial nerve was preserved anatomically in 83 (79.1%) patients. Using the House-Brackmann grading system, facial nerve function was assessed immediately after surgery, at the time of discharge and 1 year after surgery. Excellent function (Grades I and II) was present in 41.0%, 41.8%, and 56.7% of patients at each time interval, respectively, with acceptable function (Grade I-IV) in 78.5% (68/87 cases) at follow-up assessment at one year. The suboccipital retrosigmoid approach resulted in good anatomical and functional preservation of the facial nerve during excision of large acoustic neuromas, with minimal other morbidity and low mortality. We recommend this approach for excision of large acoustic neuromas.

Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery

PURPOSE

To analyze the relationship between hearing preservation after gamma knife radiosurgery (GKR) for vestibular schwannoma (VS) and some volumetric and dosimetric parameters of the intracanalicular components of VS.

METHODS AND MATERIALS

This study included 82 patients with a VS treated by GKR; all patients had no NF2 disease, a Gardner-Robertson hearing class 1-4 before treatment, a marginal dose of 12 Gy, and a radiologic and audiologic follow-up > or =1 year post-GKR. The volume of both the entire tumor and the intracanalicular part of the tumor and the mean and integrated dose of these two volumes were correlated to the auditory outcomes of patients.

RESULTS

At last hearing follow-up, 52 patients had no hearing worsening, and 30 patients had an increase of > or =1 class on Gardner-Robertson classification. We found that hearing preservation after GKR is significantly correlated with the intracanalicular tumor volume, as well as with the integrated dose delivered to the intracanalicular tumor volume.

CONCLUSIONS

Some volumetric and dosimetric parameters of the intracanalicular part of the tumor influence hearing preservation after GKR of VS. Consequently, we advise the direct treatment of patients with preserved functional hearing and a VS including a small intracanalicular volume.

Peripheral and cranial nerve sheath tumors

PURPOSE OF REVIEW

The intention of the authors is to provide the reader with an overview of the recent advances in the diagnosis and treatment of nerve sheath tumors. Vestibular schwannomas, neurogenetic syndromes such as schwannomatosis and multiple isolated neurofibromas, and malignant peripheral nerve sheath tumors are covered in this review.

RECENT FINDINGS

Over the last year, literature focusing on different management strategies for patients with vestibular schwannomas dominated the field. Surgical options for this group of patients are changing. Stereotactic radiation is also employed more frequently with promising results. New insights into the biology of peripheral nerve tumor development and growth, including expression of vascular endothelial growth factor by vestibular schwannomas and the role of Notch signaling in malignant transformation of benign neurofibromas have been described. Diagnostic criteria for schwannomatosis, a recently described condition, are being developed. Several cases of multiple isolated neurofibromas and spinal neurofibromas were reported.

SUMMARY

Peripheral nerve tumors are classified according to the specific features of cellular differentiation. The most common types include schwannoma and neurofibroma. These tumors can occur sporadically or as manifestations of genetic syndromes such as neurofibromatosis types 1 and 2 or schwannomatosis. The majority of peripheral nerve tumors are benign but malignant transformation does occur. Metastatic tumors can also affect peripheral nerves. The diagnostic modality of choice is magnetic resonance imaging. Positron emission tomography is a useful technique in the presurgical differentiation between benign and malignant peripheral nerve sheath tumors. Treatment is directed towards symptomatic control. Surgery, radiation and, in rare instances, chemotherapy are the major treatment modalities employed.

Long-term outcome of stereotactic radiosurgery (SRS) in patients with acoustic neuromas

PURPOSE

To evaluate the effectiveness and long-term outcome of stereotactic radiosurgery (SRS) for acoustic neuromas (AN).

PATIENTS AND METHODS

Between 1990 and 2001, we treated 26 patients with 27 AN with SRS. Two patients suffered from neurofibromatosis type 2. Before SRS, a subtotal or total resection had been performed in 3 and in 5 patients, respectively. For SRS, a median single dose of 13 Gy/80% isodose was applied.

RESULTS

The overall actuarial 5-year and 10-year tumor control probability in all patients was 91%. Two patients developed tumor progression after SRS at 36 and 48 months. Nineteen patients (73%) were at risk of treatment-related facial nerve toxicity; of these, 1 patient developed a complete facial nerve palsy after SRS (5%). A total of 93% of the lesions treated were at risk of radiation-induced trigeminal neuralgia. Two patients (8%) developed mild dysesthesia of the trigeminal nerve after SRS. The hearing preservation rate in patients with useful hearing before SRS was 55% at 9 years.

CONCLUSION

Stereotactic radiosurgery results in good local control rates of AN and the risk of cranial nerve toxicities is acceptable. As toxicity is lower with fractionated stereotactic radiotherapy, SRS should be reserved for smaller lesions.

Management of Vestibular Schwannomas that Enlarge after Stereotactic Radiosurgery: Treatment Recommendations Based on a 15 Year Experience

OBJECTIVE

Stereotactic radiosurgery is an effective alternative to surgical resection for the majority of patients with vestibular schwannomas (VS). However, after radiosurgery, the imaging characteristics of VSs are variable, and correct interpretation is critical to prevent unnecessary surgery for these patients.

METHODS

A retrospective study of 208 consecutive patients with unilateral VS having radiosurgery between March 1990 and December 2001. Thirty (14%) patients had tumors that enlarged at least 2 mm after radiosurgery. The median follow-up after radiosurgery was 56 months (range 24-132 mo).

RESULTS

The median time to tumor enlargement was 9 months (5-60 mo). The median volume increase was 75%. A loss of central enhancement was noted in 28 (93%) patients. Six (20%) patients had new symptoms noted at the time of tumor enlargement including hemifacial spasm (n = 2), ataxia (n = 2), trigeminal neuralgia (n = 1), and facial numbness (n = 1). Additional treatment was performed at the time of initial enlargement in 3 patients (resection, n = 2; ventriculoperitoneal shunt, n = 1). In the 28 patients who did not undergo resection at the time of initial enlargement, three patterns were identified on later imaging. Sixteen (57%) patients showed eventual tumor regression (type 1), and eight (29%) patients had tumors that increased and remained larger but did not show progressive enlargement (type 2). Four (14%) patients showed progressive enlargement on serial imaging (type 3) and underwent additional treatment (resection, n = 3; stereotactic radiation therapy, n = 1).

CONCLUSION

Tumor expansion after VS radiosurgery rarely denotes a failed procedure, and the majority of patients only require further imaging. Approximately one third of tumors that enlarge will remain increased in size compared with the time of radiosurgery but will not show sequential growth. Additional tumor treatment should be reserved only for patients who demonstrate progressive tumor enlargement on serial imaging (2% in this series).

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.

Stereotactic radiosurgery, microsurgery, and expectant management of acoustic neuroma: basis for informed consent

There is diversity in the techniques and instrumentation used to perform stereotactic radiosurgery. The field continues to evolve rapidly, and improvements are being made in accuracy, effective radiation dose, and parameters necessary to maximize patient outcome. Stereotactic radio-surgery, like any other treatment modality, has advantages and disadvantages that must be discussed with a patient who has an acoustic neuroma or other skull base tumor. An informed decision to pursue observation,microsurgery, stereotactic radiosurgery, or a combination of these methods must be made, and it remains the responsibility of the surgeon to provide a balanced view of the relative advantages and disadvantages of each method.

Management of acoustic neuromas with fractionated stereotactic radiotherapy (FSRT): Long-term results in 106 patients treated in a single institution

PURPOSE

To assess the long-term outcome and toxicity of fractionated stereotactic radiotherapy for acoustic neuromas in 106 patients treated in a single institution.

PATIENTS AND METHODS

Between October 1989 and January 2004, fractionated stereotactic radiotherapy (FSRT) was performed in 106 patients with acoustic neuroma (AN). The median total dose applied was 57.6 Gy in median single fractions of 1.8 Gy in five fractions per week. The median irradiated tumor volume was 3.9 mL (range, 2.7-30.7 mL). The median follow-up time was 48.5 months (range, 3-172 months).

RESULTS

Fractionated stereotactic radiotherapy was well tolerated in all patients. Actuarial local tumor control rates at 3- and 5- years after FSRT were 94.3% and 93%, respectively. Actuarial useful hearing preservation was 94% at 5 years. The presence of neurofibromatosis (NF-2) significantly adversely influenced hearing preservation in patients that presented with useful hearing at the initiation of RT (p = 0.00062). Actuarial hearing preservation without the diagnosis of NF-2 was 98%. In cases with NF-2, the hearing preservation rate was 64%. Cranial nerve toxicity other than hearing impairment was rare. The rate of radiation induced toxicity to the trigeminal and facial nerve was 3.4% and 2.3%, respectively.

CONCLUSION

Fractionated stereotactic radiotherapy is safe and efficacious for the treatment of AN, with mild toxicity with regard to hearing loss and cranial nerve function. FSRT might be considered as an equieffective treatment modality compared to neurosurgery and therefore represents an interesting alternative therapy for patients with AN.

Acute neurological complications following gamma knife surgery for vestibular schwannoma

The authors describe an acute facial and acoustic neuropathy following gamma knife surgery (GKS) for vestibular schwannoma (VS). This 39-year-old woman presenting with tinnitus underwent GKS for a small right-sided intracanalicular VS, receiving a maximal dose of 26 Gy and a tumor margin dose of 13 Gy to the 50% isodose line. Thirty-six hours following treatment she presented with nausea, vomiting, vertigo, diminished hearing, and a House-Brackmann Grade III facial palsy. She was started on intravenous glucocorticosteroid agents, and over the course of 2 weeks her facial function returned to House-Brackmann Grade I. Unfortunately, her hearing loss persisted. A magnetic resonance (MR) image obtained at the time of initial deterioration demonstrated a significant decrease in tumor enhancement but no change in tumor size or peritumoral edema. Subsequently, the patient experienced severe hemifacial spasms, which persisted for a period of 3 weeks and then progressed to a House-Brackmann Grade V facial palsy. During the next 3 months, the patient was treated with steroids and in time her facial function and hearing returned to baseline levels. Results of MR imaging revealed transient enlargement (3 mm) of the tumor, which subsequently returned to its baseline size. This change corresponded to the tumor volume increase from 270 to 336 mm3. The patient remains radiologically and neurologically stable at 10 months posttreatment. This is the first detailed report of acute facial and vestibulocochlear neurotoxicity following GKS for VS that improved with time. In addition, MR imaging findings were indicative of early neurotoxic changes. A review of possible risk factors and explanations of causative mechanisms is provided.

Stereotactic Radiosurgery for Vestibular Schwannomas: Analysis of 317 Patients Followed More Than 5 Years

OBJECTIVE:

Many investigators have reported successful treatment of vestibular schwannomas with gamma knife radiosurgery (GKRS). However, long-term outcomes should be evaluated before concluding that GKRS is truly safe and effective for the treatment of vestibular schwannomas.

METHODS:

Between May 1991 and December 1998, 346 consecutive patients (excluding those presenting with neurofibromatosis Type 2) were treated with GKRS. Of these, 317 patients were assessed. Twenty-nine patients were lost to follow-up within 5 years.

RESULTS:

The median follow-up period was 7.8 years. Of 301 patients who underwent serial follow-up imaging, two (1%) experienced complete remission, 184 (61%) experienced partial remission, 93 (31%) had stable tumors, and 22 (7%) experienced treatment failure. The actuarial 5- or 10-year progression-free survival (PFS) rate was 93 and 92%, respectively. Tumors less than 15 cm3 in volume (10-yr PFS, 96%; P &lt; 0.001) or which did not compress the brainstem and deviate the fourth ventricle (10-yr PFS, 97%; P = 0.008) resulted in significantly better PFS rates. Failure of treatment usually occurred within 3 years. When the tumor was treated with a marginal dose of 13 Gy or less, the hearing preservation rate was 68%, transient facial palsy developed at a rate of 1%, and facial numbness developed at a rate of 2%.

CONCLUSION:

GKRS proved to be a safe and effective treatment for patients followed longer than 5 years who presented with tumors with a volume of less than 15 cm3 and who did not have significant fourth ventricle deviation. Good functional outcomes were observed in this group of patients.

Stereotactic Radiotherapy for Vestibular Schwannomas: Favorable Outcome with Minimal Toxicity

OBJECTIVE:

To determine the outcome and toxicity in patients with vestibular schwannomas treated with conventionally fractionated stereotactic radiotherapy (SRT) and to identify prognostic factors that are predictive of outcome.

METHODS:

Between 1992 and 2001, 70 patients with vestibular schwannomas were treated with linear accelerator-based SRT in our institutions. Eleven patients had neurofibromatosis Type II (NF2). The median age was 53 years (range, 17–82 yrs). The median tumor volume was 2.4 cm3 (range, 0.05–21.1 cm3). The indications for SRT were distributed as follows: 47% newly diagnosed, 31% progressive tumors after watchful waiting, 3% adjuvant postoperative radiation, and 19% recurrent tumors after surgical resection. The median dose was 54 Gy in 1.8 Gy per fraction, prescribed to 95% of the isodose line. Relocatable stereotactic frames were used for daily treatments. The median follow-up was 45.3 months.

RESULTS:

Tumor recurrence was defined as progressive enlargement of tumor on follow-up magnetic resonance imaging studies. One patient had a tumor recurrence at 38 months after SRT. The actuarial tumor control rates were 100 and 98% at 3 and 5 years, respectively. Three patients with a median tumor volume of 16.2 cm3 required surgical resection for persistent or increasing symptoms at a median of 37 months. The actuarial freedom from resection rates were 98 and 92% at 3 and 5 years, respectively. In multivariate analysis, tumor volume at time of treatment was predictive for neurosurgical intervention (surgical resection or shunt placement) after SRT (P = 0.001). The 3- and 5-year actuarial rates of freedom from any neurosurgical intervention were 100 and 97% for patients with tumor volume less than 8 cm3 and 74 and 47% respectively for patients with tumor of at least 8 cm3 (P &lt; 0.0001). The 3-year actuarial rates of facial and trigeminal nerve preservation were 99 and 96%, respectively. Surgery before SRT was predictive of posttreatment trigeminal neuropathy. The 3-year actuarial rates of freedom from trigeminal neuropathy were 86 and 98% for patients with and without previous resection, respectively (P = 0.04). There was no difference in tumor control and cranial nerve function preservation rates seen in NF2 patients compared with non-NF2 patients. No second primary cancer or malignant transformation was observed.

CONCLUSION:

SRT in the conventionally fractionated approach results in a very favorable outcome with minimal toxicity, with results comparable to those of the best of the radiosurgery series. Patients with large tumors are more likely to undergo neurosurgical interventions after SRT. Patients who have undergone previous surgery are at increased risk of developing trigeminal neuropathy.

Linear accelerator radiosurgery for vestibular schwannoma: measuring tumor volume changes on serial three-dimensional spoiled gradient-echo magnetic resonance images

OBJECT

The authors report on a series of 46 patients harboring vestibular schwannomas (VSs) treated using linear accelerator (LINAC) radiosurgery and an analysis of serial magnetic resonance (MR) imaging data, specifically the changes in tumor volume.

METHODS

Fifty-three consecutive patients underwent LINAC radiosurgery for VS between 1993 and 2002. Seven of these patients were lost to follow up. Three-dimensional (3D) spoiled gradient-echo (SPGR) MR imaging was performed at 3- to 4-month intervals after radiosurgery. Tumor volume was measured on Gd-enhanced MR images of each slice. The median duration of follow-up MR imaging studies was 56.5 months (range 12-120 months). Follow-up imaging studies were conducted for longer than 1 year in 42 of 53 patients. Tumor volume changes were categorized into four types: enlargement (eight lesions [19%]), no change (two lesions [4.8%]), transient enlargement followed by shrinkage (19 lesions [45.2%]), and direct shrinkage (13 lesions [31%]). Two cases (4.8%) with twice the initial tumor volume required repeated radiosurgery. All cases of transient enlargement had subsequent shrinkage within 2 years after radiosurgery. Nine (21.4%) of 42 patients demonstrated ventricular enlargement on MR images obtained after radiosurgery. Three patients (7.1%) required placement of a ventriculoperitoneal shunt because of symptomatic hydrocephalus, and another four cases (9.5%) spontaneously resolved.

CONCLUSIONS

Volume measurement on 3D-SPGR MR imaging was a suitable method to assess tumor changes. Volume changes beyond twofold or continuous enlargement for longer than 2 years after radiosurgery are key criteria in rating the effects of radiation. Some cases of hydrocephalus after radiosurgery resolved spontaneously and their rates of occurrence were similar to the typical incidence of hydrocephalus associated with VS.

Radiosurgery for vestibular schwannomas

BACKGROUND

Radiosurgery has been established as an important alternative to microsurgery. We report our experience with radiosurgery for tumor control and the complications of unilateral vestibular schwannomas.

METHODS

We reviewed our early experience regarding clinical presentation, management and outcomes in 45 patients with acoustic schwannomas who underwent gamma knife stereotactic radiosurgery. The median follow-up period was 25 months (range, 6-48 months). Thirteen patients had undergone 1 or more previous resections before radiosurgery; 32 underwent radiosurgery as the first procedure. Median tumor volume was 4.5 mL (range, 0.5-30.0), and median radiotherapy dose was 11.5 Gy (range, 10.5-14.0 Gy).

RESULTS

Tumor control was achieved in 43 patients (95.6%). Loss of central contrast enhancement was a characteristic change and was noted in 29 patients (64.4%). Reduction in tumor size was shown in 15 patients (33.3%). Thirteen patients (28.9%) had good or serviceable hearing preoperatively, and in all of these, the preoperative status was retained immediately after radiosurgery. At follow-up, however, 10 patients (76.9%) had preserved hearing and 3 (23.1%) had reduced hearing on the treated side. Hearing in 1 patient that was not serviceable preoperatively later improved to a serviceable level. No patients had delayed facial palsy or lower cranial nerve dysfunction, but one had delayed trigeminal sensory loss.

CONCLUSION

Radiosurgery achieved a high tumor control rate and a relatively low post-radiosurgical complication rate for acoustic neuromas.

Staged Stereotactic Irradiation for Acoustic Neuroma

OBJECTIVE:

Stereotactic radiosurgery has proven effective in the treatment of acoustic neuromas. Prior reports using single-stage radiosurgery consistently have shown excellent tumor control, but only up to a 50 to 73% likelihood of maintaining hearing at pretreatment levels. Staged, frame-based radiosurgery using 12-hour interfraction intervals previously has been shown by our group to achieve excellent tumor control while increasing the rate of hearing preservation at 2 years to 77%. The arrival of CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery now makes it more practical to treat acoustic neuroma with a staged approach. We hypothesize that such factors may further minimize injury of adjacent cranial nerves. In this retrospective study, we report our experience with staged radiosurgery for managing acoustic neuromas.

METHODS:

Since 1999, the CyberKnife has been used to treat more than 270 patients with acoustic neuroma at Stanford University. Sixty-one of these patients have now been followed up for a minimum of 36 months and form the basis for the present clinical investigation. Among the treated patients, the mean transverse tumor diameter was 18.5 mm, whereas the total marginal dose was either 18 or 21 Gy using three 6- or 7-Gy fractions. Audiograms and magnetic resonance imaging were obtained at 6-months intervals after treatment for the first 2 years and then annually thereafter.

RESULTS:

Of the 61 patients with a minimum of 36 months of follow-up (mean, 48 mo), 74% of patients with serviceable hearing (Gardner-Robinson Class 1–2) maintained serviceable hearing at the last follow-up, and no patient with at least some hearing before treatment lost all hearing on the treated side. Only one treated tumor (2%) progressed after radiosurgery; 29 (48%) of 61 decreased in size and 31 (50%) of the 61 tumors were stable. In no patients did new trigeminal dysfunction develop, nor did any patient experience permanent injury to their facial nerve; two patients experienced transient facial twitching that resolved in 3 to 5 months.

CONCLUSION:

Although still preliminary, these results indicate that improved tumor dose homogeneity and a staged treatment regimen may improve hearing preservation in acoustic neuroma patients undergoing stereotactic radiosurgery.

Gamma knife surgery for epilepsy related to hypothalamic hamartomas

OBJECTIVE

Drug resistant epilepsy associated with hypothalamic hamartoma (HH) can be cured by microsurgical resection of the lesion. Morbidity and mortality risks of microsurgery in this area are significant. Gamma Knife Surgery's (GKS) reduced invasivity seems to be well adapted. In view of the severity of the disease and risks of surgical resection it is crucial to evaluate GKS for this indication. A first retrospective study has shown a very good safety and efficacy level but for a more reliable evaluation a prospective study would be required.

METHODS

Between Oct 1999 and July 2002, 30 patients with HH and associated severe epilepsy were included. Seizure semiology (video EEG) and frequency, behavioural disturbances, neuropsychological performance, endocrinological status, sleep electroclinical abnormalities, MR imaging, and visual function were systematically evaluated before and after GKS (6, 12, 18, 24, 36 months). Twenty patients had experienced precocious puberty at a median age of 3,7 (0-9). Range of maximum diameter was from 7,5 to 23 mm with only 3 larger than 18 mm. The median marginal dose was 17 gy (14-20).

RESULTS

Sufficient follow up for final evaluation is not yet available. Only 6 patients have a follow-up of more than 12 months and 19 more than 6 months. However a lot of very dramatic changes did occur during that period in this group. Among the 19 patients with more than 6 months of follow-up, a lot had already experienced an increase of gelastic seizures around 3 months (3), an improvement in their seizure rate (18), behaviour (9), sleep (3), and EEG background activity (3), a cessation of partial complex seizures (7). No complications have occurred till now except one patient experiencing at 5 months a hyperthermia without infection and concomitant increase of gelastic seizures both ceasing suddenly and spontaneously after 15 days.

CONCLUSION

Our first results indicate that GKS is as effective as microsurgical resection and very much safer. GKS also allows to avoid the vascular risk related to radiofrequency lesioning or stimulation. The disadvantage of radiosurgery is its delayed action. Longer follow-up is mandatory for a serious evaluation of the role of GKS. Results are faster and more complete in patients with smaller lesions inside the 3rd ventricle (grade II). The early effect on subclinical discharges turns out to play a major role in the dramatic improvement of sleep quality, behaviour, developmental acceleration at school.

Evolution of vestibular schwannoma surgery: the long journey to current success

The extraordinary improvement of patient outcome after surgical treatment for vestibular schwannomas is relatively recent and has occurred mainly over the last 30 years. The introduction of microsurgical techniques has resulted in increasing degrees of precise anatomical and functional preservation of the facial and cochlear nerves. An expanded microsurgical technique accompanied by continuous electrophysiological monitoring has resulted in marked changes in the primary goals for this surgery. Whereas in the past the primary goal of vestibular schwannoma management was to preserve the patient's life, the objective in vestibular schwannoma treatment today is to preserve neurological function.

Long-term follow-up examinations show negligible recurrence rates, indicating that the aim of preservation of nerve function does not limit the completeness of tumor removal with modern neurosurgical techniques. Despite these advances in preserving the anatomical integrity of, for example, the cochlear nerve, losses of function and even deafness may occur postoperatively in some cases. Current biological and technical research in experimental and clinical settings addresses these problems. In this article, the authors report in detail the developments achieved in vestibular schwannoma surgery and the great clinicians to whom these results can be credited.

Radiosurgery of vestibular schwannomas: summary of experience in 829 cases

OBJECT

Management options for vestibular schwannomas (VSs) have greatly expanded since the introduction of stereotactic radiosurgery. Optimal outcomes reflect long-term tumor control, preservation of cranial nerve function, and retention of quality of life. The authors review their 15-year experience.

METHODS

Between 1987 and 2002, some 829 patients with VSs underwent gamma knife surgery (GKS). Dose selection, imaging, and dose planning techniques evolved between 1987 and 1992 but thereafter remained stable for 10 years. The average tumor volume was 2.5 cm3. The median margin dose to the tumor was 13 Gy (range 10-20 Gy). No patient sustained significant perioperative morbidity. The average duration of hospital stay was less than 1 day. Unchanged hearing preservation was possible in 50 to 77% of patients (up to 90% in those with intracanalicular tumors). Facial neuropathy risks were reduced to less than 1%. Trigeminal symptoms were detected in less than 3% of patients whose tumors reached the level of the trigeminal nerve. Tumor control rates at 10 years were 97% (no additional treatment needed).

CONCLUSIONS

Superior imaging, multiple isocenter volumetric conformal dose planning, and optimal precision and dose delivery contributed to the long-term success of GKS, including in those patients in whom initial microsurgery had failed. Gamma knife surgery provides a low risk, minimally invasive treatment option for patients with newly diagnosed or residual VS. Cranial nerve preservation and quality of life maintenance are possible in long-term follow up.

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.

Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.

Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3 (range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.

A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.

Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

Object.The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.

Methods.A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3(range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.

A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.

Conclusions.Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Long-term results of Leksell gamma knife surgery for trigeminal schwannomas

Object. The authors evaluated the long-term efficacy of gamma knife surgery (GKS) in patients with trigeminal schwannomas.

Methods. Fifty-six patients, 31 women and 25 men (mean age 42 years), underwent GKS for trigeminal schwannomas. Fourteen had previously undergone surgery, and GKS was the primary treatment in the remaining 42 patients. The mean target volume was 8.7 cm3 (range 0.8–33 cm3); the mean maximum dose was 27 Gy (range 20–40 Gy); the mean tumor margin dose was 13.3 Gy (range 10–15 Gy); and the mean follow-up period was 68 months (range 27–114 months).

Disappearance of the tumor occurred in seven patients. An obvious decrease in tumor volume was observed in 41 patients, four tumors remained unchanged, and four tumors progressed at 5, 26, 30, and 60 months, respectively. One patient with disease progression died of tumor progression at 36 months after GKS. The tumor growth control rate in this group was 93% (52 of 56 cases).

Mild numbness or diplopia was relieved completely in 14 patients. Improvement of other neurological deficits was demonstrated in 25 patients. Trigeminal nerve dysfunction was either unchanged or slightly worse in 13 patients after GKS. Four patients experienced mild symptom deterioration related to tumor progression.

Conclusions. Radiosurgery proved to be an effective treatment for small- and medium-sized trigeminal schwannomas. Some larger tumors are also suitable for radiosurgery if there is no significant brainstem compression.

Gamma knife surgery for glomus jugulare tumors: an intermediate report on efficacy and safety

OBJECT

Glomus jugulare tumors are rare tumors that commonly involve the middle ear, temporal bone, and lower cranial nerves. Resection, embolization, and radiation therapy have been the mainstays of treatment. Despite these therapies, tumor control can be difficult to achieve particularly without undo risk of patient morbidity or mortality. The authors examine the safety and efficacy of gamma knife surgery (GKS) for glomus jugulare tumors.

METHODS

A retrospective review was undertaken of the results obtained in eight patients who underwent GKS for recurrent, residual, or unresectable glomus jugulare tumors. The median radiosurgical dose to the tumor margin was 15 Gy (range 12-18 Gy). The median clinical follow-up period was 28 months, and the median period for radiological follow up was 32 months. All eight patients demonstrated neurological stability or improvement. No cranial nerve palsies arose or deteriorated after GKS. In the seven patients in whom radiographic follow up was obtained, the tumor size decreased in four and remained stable in three.

CONCLUSIONS

Gamma knife surgery would seem to afford effective local tumor control and preserves neurological function in patients with glomus jugulare tumors. If long-term results with GKS are equally efficacious, the role of stereotactic radiosurgery will expand.

Acoustic Neuromas after Failed Radiation Therapy: Challenges of Surgical Salvage

OBJECTIVES

As stereotactic radiation has emerged as a treatment option for acoustic neuromas, cases that require surgical salvage after unsuccessful radiation have emerged. We present a comparison of the technical challenges faced by the surgeons in the treatment of irradiated versus nonirradiated acoustic neuromas.

STUDY DESIGN

Matched case-control series.

METHODS

We identified nine patients with acoustic neuromas that required surgical resection after radiation therapy. Cases were performed with suboccipital and translabyrinthine approaches. Nine nonirradiated case-control subjects matched for age, sex, tumor size, and surgical approach were identified for purposes of general comparison. Operative findings and outcomes were compared for the two groups.

RESULTS

Surgical removal was found to be significantly more difficult after radiation therapy because of increased fibrosis and adhesion to adjacent nervous structures, particularly at the porus acousticus. Excessive scarring hindered identification of the facial nerve and added uncertainty as to the completeness of tumor removal. Decompression of the internal auditory canal (IAC) dura and resection of neoplasm in the IAC before cerebellopontine angle dissection was required for facial nerve identification. Operative time was significantly longer for irradiated cases, and facial nerve outcomes tended to be poorer, particularly when facial nerve dysfunction prompted the salvage procedure.

CONCLUSIONS

Surgical salvage of acoustic neuromas after radiation therapy is feasible, but it presents technical challenges beyond that associated with primary surgical therapy. Poorer outcomes of postoperative cranial nerve status were caused primarily by anatomic changes at the nerve/tumor interface. As surgical experience with the irradiated acoustic neuroma grows, operative observations should be incorporated into the counsel provided to patients with acoustic neuromas as they weigh different management options.

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.

Long-term results of Leksell gamma knife surgery for trigeminal schwannomas

Object. The authors evaluated the long-term efficacy of gamma knife surgery (GKS) in patients with trigeminal schwannomas.

Methods. Fifty-six patients, 31 women and 25 men (mean age 42 years), underwent GKS for trigeminal schwannomas. Fourteen had previously undergone surgery, and GKS was the primary treatment in the remaining 42 patients. The mean target volume was 8.7 cm3 (range 0.8–33 cm3); the mean maximum dose was 27 Gy (range 20–40 Gy); the mean tumor margin dose was 13.3 Gy (range 10–15 Gy); and the mean follow-up period was 68 months (range 27–114 months).

Disappearance of the tumor occurred in seven patients. An obvious decrease in tumor volume was observed in 41 patients, four tumors remained unchanged, and four tumors progressed at 5, 26, 30, and 60 months, respectively. One patient with disease progression died of tumor progression at 36 months after GKS. The tumor growth control rate in this group was 93% (52 of 56 cases).

Mild numbness or diplopia was relieved completely in 14 patients. Improvement of other neurological deficits was demonstrated in 25 patients. Trigeminal nerve dysfunction was either unchanged or slightly worse in 13 patients after GKS. Four patients experienced mild symptom deterioration related to tumor progression.

Conclusions. Radiosurgery proved to be an effective treatment for small- and medium-sized trigeminal schwannomas. Some larger tumors are also suitable for radiosurgery if there is no significant brainstem compression.

Radiosurgery of vestibular schwannomas: summary of experience in 829 cases

Object. Management options for vestibular schwannomas (VSs) have greatly expanded since the introduction of stereotactic radiosurgery. Optimal outcomes reflect long-term tumor control, preservation of cranial nerve function, and retention of quality of life. The authors review their 15-year experience.

Methods. Between 1987 and 2002, some 829 patients with VSs underwent gamma knife surgery (GKS). Dose selection, imaging, and dose planning techniques evolved between 1987 and 1992 but thereafter remained stable for 10 years. The average tumor volume was 2.5 cm3. The median margin dose to the tumor was 13 Gy (range 10–20 Gy).

No patient sustained significant perioperative morbidity. The average duration of hospital stay was less than 1 day. Unchanged hearing preservation was possible in 50 to 77% of patients (up to 90% in those with intracanalicular tumors). Facial neuropathy risks were reduced to less than 1%. Trigeminal symptoms were detected in less than 3% of patients whose tumors reached the level of the trigeminal nerve. Tumor control rates at 10 years were 97% (no additional treatment needed).

Conclusions. Superior imaging, multiple isocenter volumetric conformal dose planning, and optimal precision and dose delivery contributed to the long-term success of GKS, including in those patients in whom initial microsurgery had failed. Gamma knife surgery provides a low risk, minimally invasive treatment option for patients with newly diagnosed or residual VS. Cranial nerve preservation and quality of life maintenance are possible in long-term follow up.

Gamma knife surgery for glomus jugulare tumors: an intermediate report on efficacy and safety

Object. Glomus jugulare tumors are rare tumors that commonly involve the middle ear, temporal bone, and lower cranial nerves. Resection, embolization, and radiation therapy have been the mainstays of treatment. Despite these therapies, tumor control can be difficult to achieve particularly without undo risk of patient morbidity or mortality. The authors examine the safety and efficacy of gamma knife surgery (GKS) for glomus jugulare tumors.

Methods. A retrospective review was undertaken of the results obtained in eight patients who underwent GKS for recurrent, residual, or unresectable glomus jugulare tumors. The median radiosurgical dose to the tumor margin was 15 Gy (range 12–18 Gy). The median clinical follow-up period was 28 months, and the median period for radiological follow up was 32 months.

All eight patients demonstrated neurological stability or improvement. No cranial nerve palsies arose or deteriorated after GKS. In the seven patients in whom radiographic follow up was obtained, the tumor size decreased in four and remained stable in three.

Conclusions. Gamma knife surgery would seem to afford effective local tumor control and preserves neurological function in patients with glomus jugulare tumors. If long-term results with GKS are equally efficacious, the role of stereotactic radiosurgery will expand.

Hearing preservation after gamma knife stereotactic radiosurgery of vestibular schwannoma

BACKGROUND

To evaluate the hearing preservation rate and to determine its prognostic factors after gamma knife (GK) stereotactic radiosurgery (SRS) in patients with vestibular schwannoma, the authors used a prospective study design to analyze these patients.

METHODS

Between December 1997 and January 2002, 25 patients with vestibular schwannoma with serviceable hearing were enrolled in the current study. The median tumor volume was 3.0 cc (0.16-9.1 cc). The prescription dose was 12.0 +/- 0.7 gray at an isodose line of 49.8 +/- 1.1%. The tumor control rate and complications were evaluated by focusing on hearing preservation and its prognostic factors.

RESULTS

Based on radiologic study, the tumor control rate was 92% during the median follow-up period of 45 months. The trigeminal and facial nerve preservation rates were 95% and 100%, respectively. Thirteen (52%) of the 25 patients preserved serviceable hearing and 9 (36%) patients retained their pre-GK G-R grade levels after GK SRS. However, 16 patients showed hearing deterioration > 20 dB within 3-6 months and this trend continued for 24 months after the treatment. The maximum radiotherapy dose delivered to the cochlear nucleus was the single, significant prognostic factor of hearing deterioration.

CONCLUSIONS

The authors concluded that a more sophisticated strategy to prevent hearing deterioration during the first 6 months post-GK SRS is necessary to improve long-term hearing preservation.

Low-dose radiosurgery for large vestibular schwannomas: long-term results of functional preservation

Object.The author conducted a study to assess the long-term results obtained in patients who underwent GKS for large vestibular schwannomas (> cochlear nerve functions were evaluated.

Methods.Twenty consecutive large tumors in 18 patients (including two cases of neurofibromatosus Type 2 [NF2]) were followed for more than 6 years. There were eight tumors that were more than 4 cm in maximum diameter. Microsurgery had already been performed prior to GKS in 11 patients (nine recurrent and two residual tumors).

Four patients (including one with NF2) died during the follow-up period of other diseases or by accident. Fourteen of 15 tumors were stable or decreased in size. Microsurgery was performed in one patient 2 years after radiosurgery. Facial nerve function was preserved in all patients and hearing preserved in four of five patients with cochlear nerve function prior to radiosurgery. No adverse effects of radiosurgery have been observed to date.

Conclusions.Gamma knife surgery seems to have a place in the low-dose treatment of selected large vestibular schwannoma in patients with a reasonable chance of retaining facial function and pretreatment hearing level. Patients with severe brainstem compression should first be undergo 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.

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.

Long-term outcomes in patients with vestibular schwannomas treated using gamma knife surgery: 10-year follow up

Object. Gamma knife surgery (GKS) has been a safe and effective treatment for vestibular schwannomas in both the short and long term, although less is known about long-term outcomes in the past 10 years. The aim of this study was to clarify long-term outcomes in patients with vestibular schwannomas treated using GKS based on techniques in place in the early 1990s.

Methods. Eighty patients harboring a vestibular schwannoma (excluding neurofibromatosis Type 2) were treated using GKS between May 1991 and December 1993. Among these, 73 patients were assessed; seven were lost to follow up. The median duration of follow up was 135 months. The mean patient age at the time of GKS was 56 years old. The mean tumor volume was 6.3 cm3, and the mean maximal and marginal radiation doses applied to the tumor were 28.4 and 14.6 Gy, respectively. Follow-up magnetic resonance images were obtained in 71 patients. Forty-eight patients demonstrated partial tumor remission, 14 had tumors that remained stable, and nine demonstrated tumor enlargement or radiation-induced edema requiring resection. Patients with larger tumors did not fare as well as those with smaller lesions. The actuarial 10-year progression-free survival rate was 87% overall, and 93% in patients with tumor volumes less than 10 cm3. No patient experienced malignant transformation.

Conclusions. Gamma knife surgery remained an effective treatment for vestibular schwannomas for longer than 10 years. Although treatment failures usually occurred within 3 years after GKS, it is necessary to continue follow up in patients to reveal delayed tumor recurrence.

Low-dose radiosurgery for large vestibular schwannomas: long-term results of functional preservation

Object. The author conducted a study to assess the long-term results obtained in patients who underwent GKS for large vestibular schwannomas (> cochlear nerve functions were evaluated.

Methods. Twenty consecutive large tumors in 18 patients (including two cases of neurofibromatosus Type 2 [NF2]) were followed for more than 6 years. There were eight tumors that were more than 4 cm in maximum diameter. Microsurgery had already been performed prior to GKS in 11 patients (nine recurrent and two residual tumors).

Four patients (including one with NF2) died during the follow-up period of other diseases or by accident. Fourteen of 15 tumors were stable or decreased in size. Microsurgery was performed in one patient 2 years after radiosurgery. Facial nerve function was preserved in all patients and hearing preserved in four of five patients with cochlear nerve function prior to radiosurgery. No adverse effects of radiosurgery have been observed to date.

Conclusions. Gamma knife surgery seems to have a place in the low-dose treatment of selected large vestibular schwannoma in patients with a reasonable chance of retaining facial function and pretreatment hearing level. Patients with severe brainstem compression should first be undergo microsurgery.

Safety and Efficacy of Tiered Limited-Dose Gamma Knife Stereotactic Radiosurgery for Unilateral Acoustic Neuroma

Stereotactic radiosurgery has become a more widely employed modality of treatment for acoustic neuromas, but controversy still arises regarding the safety and efficacy of the technique. In general, radiation doses have been reduced over time. Since beginning treatments of acoustic neuromas with the Gamma Knife at the University of Miami/Jackson Memorial Medical Center in 1994, a dose regimen was adopted by the first author employing limited doses selected on the basis of tumor size with the anterior and medial regions of the prescription isodose surface kept just inside the gadolinium-enhanced limit of the tumor, in order to protect the facial nerve and brainstem. The records of patients treated for unilateral tumors were retrospectively reviewed. Fifty-two patients, aged 23-83 years, were treated with peripheral tumor doses of 10-14 Gy at the 45-70% isodoses. No patient developed new facial weakness or sensory loss; 3 patients had minor transient facial twitching within a few months of treatment. Of 34 patients followed more than 1 year (range 14-100 months, mean 43.4 months, median 37 months), 17 tumors reduced in size, 16 remained unchanged, and 1 increased in size. One patient, who had radiosurgery as planned postoperative adjuvant treatment after partial resection of a large tumor, developed an enlarging peritumoral arachnoid cyst that required surgical resection 79 months after radiosurgery. Patients with good pretreatment hearing retained approximately the same subjective level of hearing. Very good control of unilateral acoustic neuroma has been achieved by a limited-dose scheme that produces minimal complications, but due to the frequently indolent course of these tumors, continued long-term monitoring will be necessary.

Quality of life following microsurgery, radiosurgery and conservative management for unilateral vestibular schwannoma

The best way to manage small and medium-sized vestibular schwannomas is currently a matter of heated debate. As these tumours are not immediately life-threatening, patients are invariably concerned about how management would affect their quality of life. Until now, no study has compared the three treatment modalities in terms of physical, psychological and social wellbeing. This study is based on a retrospective database analysis and postal questionnaire survey of unilateral vestibular schwannoma patients who had either been managed conservatively, or treated with microsurgery or radiosurgery. The results showed that: quality of life (measured by the Glasgow Benefit Inventory) deteriorated after microsurgery, particularly for small tumours; conservative management did not lead to a change in quality of life, and there was a trend towards poorer quality of life following radiosurgery. The findings suggest that a conservative management approach may be more appropriate for small tumours, and that patients who are due to undergo microsurgery or radiosurgery may benefit from counselling about the potential impact of treatment on quality of life.

Gamma Knife Radiosurgery for Acoustic Neuromas Performed by a Neurotologist: Early Experiences and Outcomes

OBJECTIVE

To assess early outcomes after Gamma knife radiosurgery of acoustic neuromas and other skull base tumors.

BACKGROUND

Gamma knife radiosurgery is one of the available methods to treat acoustic neuromas, in addition to micro-surgical resection. Neuro-otologists have long been associated with microsurgical resection of these tumors; however, the application of Gamma knife radiosurgery to the treatment of these tumors by neuro-otologists has not been previously described.

SETTING

Acoustic Neuroma and Skull Base Surgery Program / Tertiary Referral Center. STUDY DESIGN/PATIENTS/INTERVENTION: Prospective clinical study of all patients treated by the senior author and our gamma knife team beginning in June 2000.

MAIN OUTCOME MEASURES

Preoperative MRI, audiometry, vestibular testing and facial nerve electromyography were completed. At six-month intervals postoperatively, audiometry, caloric testing and MRI were performed to determine thresholds and speech discrimination ability, vestibular function, and the size of the tumor.

RESULTS

From June 2000 until March 2004, 38 patients were treated, and these included 33 acoustic neuromas, two meningiomas, one glomus jugulare tumor, and two facial neuromas. Greater than 36 month follow-up was available in 7 patients, > 24 months in 24, > 12 months in 31, and > 6 months in 34 patients. Statistically significant reduction in tumor size was seen over time, and tumor control was achieved in all but two patients. Various patterns of changes in auditory function, both in threshold and speech discrimination were observed in either positive or negative directions.

CONCLUSIONS

Preliminary experience with Gamma knife radiosurgery indicates that this treatment method represents another option for neuro-otologists to use in managing patients with skull base tumors.

Acoustic neuroma radiosurgery with marginal tumor doses of 12 to 13 gy

PURPOSE

To define tumor control and clinical outcomes of radiosurgery to marginal tumor doses of 12-13 Gy for unilateral acoustic neuroma patients.

METHODS AND MATERIALS

Three hundred thirteen patients with previously untreated unilateral acoustic neuromas (vestibular schwannomas) underwent gamma knife radiosurgery between February 1991 and February 2001 with marginal tumor doses of 12-13 Gy (median, 13 Gy). Median follow-up was 24 months (maximum, 115 months; 36 patients with > or =60 months). Maximum doses were 20-26 Gy (median, 26 Gy), and treatment volumes were 0.04-21.4 mL (median, 1.1 mL).

RESULTS

The actuarial 6-year clinical tumor control rate (no requirement for surgical intervention) for the entire series was 98.6 +/- 1.1%. Two patients required tumor resection; one had a complete resection for solid tumor growth and one required partial resection for an enlarging adjacent subarachnoid cyst. Six-year actuarial rates for preservation of facial nerve function, normal trigeminal nerve function, unchanged hearing level, and useful hearing were 100%, 95.6 +/- 1.8%, 70.3 +/- 5.8%, and 78.6 +/- 5.1%, respectively. The risk of developing trigeminal neuropathy correlated with increasing tumor volume (p = 0.038).

CONCLUSIONS

Acoustic neuroma radiosurgery with doses of 12-13 Gy provides high rates of tumor control and cranial nerve preservation.

Audiologic and treatment outcomes after linear accelerator–based stereotactic irradiation for acoustic neuroma

PURPOSE

Although surgical excision is the traditional treatment modality for acoustic neuroma, radiotherapy (RT) is gaining momentum as an alternative. This is particularly evident in patients with useful hearing, in whom fractionated RT offers the potential for hearing preservation. Our objective was to determine the disease control, hearing preservation (via audiograms), and toxicity rates after linear accelerator-based stereotactic radiation for acoustic neuroma.

METHODS AND MATERIALS

A total of 72 acoustic neuroma patients underwent stereotactic irradiation and had at least 6 months of follow-up between October 1997 and March 2002. Of these, 45 received single-fraction stereotactic radiosurgery (SRS) and 27 received fractionated stereotactic radiotherapy (SRT). Before treatment, all SRS patients were functionally deaf and 23 of 25 SRT patients had useful hearing in the affected ear. The minimal peripheral dose was 12 Gy and 45 Gy in all SRS and SRT patients, respectively. Tumor control, toxicity, and hearing preservation were recorded.

RESULTS

The median follow-up in the SRS and SRT groups was 27 and 26 months, respectively. No tumor progression was seen after SRS and SRT. On the basis of the audiogram criteria, the 1-year and 2-year hearing preservation rate was 85% and 57%, respectively. The mean pre- and post-SRT speech recognition threshold was 20 and 38 dB, respectively. The mean proportion of pre- and post-SRT speech discrimination was 91% and 59%, respectively.

CONCLUSION

Stereotactic RT achieves good local control, with acceptable toxicity. RT fractionation appears to provide encouraging rates of hearing preservation.

Isolated Plexiform Neurofibroma: Treatment with Three-Dimensional Conformal Radiotherapy

OBJECTIVES

To present a case of an unusual benign tumor of the tongue treated successfully with radiotherapy.

STUDY DESIGN

Case report.

METHODS

Retrospective chart review.

RESULTS

A 60-year-old man presented with a painful submucosal lesion of the tongue base. Computed tomography showed an infiltrative soft-tissue mass involving the left base of the tongue. Operative biopsy revealed plexiform neurofibroma. Because of the patient's operative risk and the potential morbidity of surgical resection, he was treated with three-dimensional conformal radiotherapy (3DCRT). His treatment was accomplished using a five-field arrangement treating exclusively the mass lesion to a total tumor dose of 60 Gy. After treatment, the patient's tongue pain resolved, and he noted minimal transient xerostomia. Serial follow-up radiographic examinations showed the base of tongue mass to be slightly smaller 4 months after treatment. The most recent follow-up magnetic resonance image reveals a further decrease in size of the mass. The patient is now over 3 years out from treatment.

CONCLUSIONS

Solitary plexiform neurofibroma of the tongue base is a rare tumor. These benign neoplasms are usually treated with either observation or surgical excision. This case demonstrates that, when significant symptoms necessitate active management, these lesions may be successfully treated with minimal morbidity using 3DCRT. The ability of this technique to deliver a conformal radiation dose to the tumor volume while sparing the surrounding normal tissues may expand the application of radiotherapy in the treatment of these benign lesions of the head and neck.

Quality of Life in patients with vestibular schwannomas managed conservatively

Since the era of magnetic resonance imaging (MRI) scanning, vestibular schwannomas are being diagnosed earlier, growth has been shown to be static in up to 70% of cases and patients have admitted to a reduced quality of life following acoustic neuroma surgery. The aim of this study was to assess the quality of life in patients with vestibular schwannomas managed conservatively. Fifty patients with a vestibular schwannoma were identified who were being managed by interval MRI scanning. Fifty patients attending the general otolaryngology clinic with similar symptoms were prospectively recruited. Each group was assessed using the short form 36 (SF-36) health survey. Both groups were adequately age and sex matched and the SF-36 scores were comparable across all eight health domains.

Intraventricular neurocytomas

The literature to date on the treatment of CNC reflects an evolution of clinical practice in neurooncology. The advent of sophisticated tools, such as MRS and molecular pathology, has facilitated more efficient diagnosis of CNC. Decreased morbidity associated with surgical intervention has resulted in better outcomes in patients undergoing resection of CNC. Prospective monitoring of treated patients with MRI coupled with judicious use of radiosurgery will likely further decrease treatment-related morbidity.