Functional outcome after gamma knife treatment in vestibular schwannoma

Radiosurgery (RS) is a noninvasive, ambulatory special neurosurgical procedure for the treatment of vestibular schwannoma (VS). We treated 123 patients with unilateral schwannomas between 1994 and 2000 at the gamma knife (GK) center in Munich using a primary stereotactic procedure. These patients were followed up until June 2004 in respect to audiological, neurological, neurootological and radiological features before and after radiosurgical intervention. The actual tumor control rate of 8.2 years (mean) after GK surgery for all patients and a single treatment was calculated to be 96.7%. The impairment of hearing was on average 18% after GK, ranking from 0% gain of hearing loss up to 90%. Facial nerve function, graded according to the House-Brackmann scale, deteriorated in none of the patients; 5.8% reported a trigeminal neuralgia. Tinnitus developed in 4.1% of the patients after RS; 13.3% had vertigo for the first time after the treatment, age apparently being a predisposing factor. Radiosurgical treatment for VS is an alternative to microsurgery (MS). It is associated with a lower rate of facial and trigeminal neuropathy, postoperative complications and hospital stay. The hearing preservation rate is equivalent to MS.

Development of a 3-D convolution / superposition algorithm for precise dose calculation in the skull

In this paper an algorithm for calculating 3-D dose distributions within the brain is introduced and adapted to the demands of modem radiosurgery. The dose calculation with this model is based on a 3-D distribution of the primary photon intensity which is calculated with a ray casting algorithm. A prelocated matrix takes into account field sizes as well as modifying elements as collimator positions (MLC), blocks, wedges and compensators. Monte Carlo precalculated monoenergetic kernels from 0.1 MeV to 50 MeV were at our disposal. The components of the spectrum were either determined by deconvoluting depth dose curves measured in water or analyzed with a Ge-Li detector system in the case of 60Co. The calculated fluence distribution has to be superposed to the complete kernel containing the spatial energy deposition. Inhomogeneities and tissue interface phenomena (rhoe, Z) have been investigated. The divergence of the rays and the curved surface of the patient are taken into account. Assuming homogenous media, it is possible to shorten the computation time by using the Fast Fourier Transformation (FFT) delivering a first overview within seconds. The algorithm was evaluated and verified under specific conditions of small fields as used in radiosurgery and compared to dose measurements and Monte Carlo calculations. In using both the fast algorithm (FFT) for mainly homogenous conditions on one hand and the very precise superposition for inhomogeneous cases on the other, this algorithm can be a very helpful instrument especially for critical locations in the skull.

Gamma-knife surgery is effective in normalising plasma insulin-like growth factor I in patients with acromegaly

OBJECTIVE

For patients in whom acromegaly persists despite pituitary surgery or drug treatment, gamma-knife surgery represents an additional treatment option. Considering carefully the different reported biochemical outcomes, the central point is whether gamma-knife radiosurgery has advantages compared to conventional radiotherapy or, furthermore, to newer medical therapies, such as long-acting somatostatin analogues or growth hormone receptor antagonists.

DESIGN AND METHODS

We report the outcome of 44 patients with acromegaly, who received gamma-knife surgery with the Leksell gamma knife. The median follow-up time was 1.9 years (0.5-4.3 years) post-radiosurgery. 43 of 44 patients had previously undergone pituitary surgery.

RESULTS

Immediately prior to gamma-knife surgery, median xULN of patients' serum IGF-I was 1.9 times above upper limit of normal (range: 0.5-8.9 xULN [multiple of upper limit of normal range]). There was a significant decline of serum IGF-I at patients' final follow-up. We found a normal age-adjusted IGF-I in 21/44 patients (xULN of IGF-I<1). Furthermore, as the number of treated patients increased, we found an improvement in remission rate, which let us assume that there was a learning effect for the gamma-knife performing team over time. In addition, the median adenoma size decreased from 1.5 ml (0.1-6.9 ml) prior to gamma-knife therapy to 0.3 ml (no rest vol. detectable-2.4 ml) at patients' last visit.

CONCLUSION

We have shown that pituitary gamma-knife surgery is effective in lowering serum IGF-I levels. At the end of the follow-up period, 48 % of our cohort had normal age-adjusted IGF-I levels.

Clinical quality standards for gamma knife radiosurgery--the Munich protocol

The clinical quality standards for outpatient gamma knife radiosurgery as developed in the German Gamma Knife Center Munich during the last ten years are described. The following aspects have been taken into account: appropriate patient selection, standardised treatment cycle, acquisition of high-quality stereotactic MR images, the integrated therapeutic concept, dose conformity and dose level, patient follow-up, quality control and scientific data analysis. Particular emphasis has been put on the importance of the interdisciplinary treatment concept by subspecialised experts. The results of the Munich concept in consideration of the described quality standards verifies that gamma knife radiosurgery is a safe and effective treatment option for well selected indications.

Quality Assurance in Stereotactic Radiosurgery/Radiotherapy according to DIN 6875-1

The new DIN ('Deutsche Industrie-Norm') 6875-1, which is currently being finalised, deals with quality assurance (QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4-mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in-house, the use of commercially available tools facilitated the QA according to the DIN 6875-1 with which our results complied.

Stereotactic Radiosurgery without Radiation Therapy Providing High Local Tumor Control of Multiple Brain Metastases from Renal Cell Carcinoma

The aim of this study was to analyse treatment effects after stereotactic radiosurgery (SRS) without whole brain radiation therapy (WBRT) as primary treatment for patients harboring brain metastases of renal cell carcinoma (RCC). During an 8-year period, 85 patients with 376 brain metastases from RCC underwent 134 outpatient SRS procedures. 65 % of all patients had multiple brain metastases. The median tumor volume was 1.2 cm (3) (range: 0.1 - 14.2 cm (3)). Mean prescribed tumor dose was 21.2 (+/- 3.2) Gy. Local/distant tumor recurrences were treated by additional SRS in cases of stable systemic disease. Overall median survival was 11.1 months after SRS. The local tumor control rate after SRS was 94 %. Most patients (78 %) died because of systemically progressing cancer. A KPS > 70 and RTOG class I were related to prolonged survival time. Patients of the RTOG groups I, II and III survived for 24.2 months, 9.2 months and 7.5 months, respectively. There was no permanent morbidity after SRS. 11 patients (12.9 %) showed transient radiogenic complications and 3 patients (3.5 %) died because of intratumoral bleedings after SRS. Stereotactic radiosurgery alone achieves excellent local tumor control rates for patients with small brain metastases from renal cell carcinoma.

Results of outpatient gamma knife radiosurgery for primary therapy of acoustic neuromas

Stereotactic radiosurgery (SRS) has been recognized as a non-invasive alternative to surgery for the treatment of acoustic neuromas. Purpose of the current study was to define the impact of outpatient gamma knife radiosurgery (GKS) for patients with unilateral sporadic acoustic neuromas treated within ten years. Follow-up images were analyzed using tumor volume measurements. 219 patients with sporadic acoustic neuromas were treated by GKS as primary therapy. Patients with NF-2 tumors were excluded. Patients were eligible for GKS up to a size limit of 12.5 cm3. The median follow up time was 6 years after radiosurgery. The local tumor control rate was high (97%). Cranial nerve morbidities were comparably low. 10% of the patients developed hearing loss after radiosurgery and one patient experienced a transient facial neuropathy (0.5%). Transient trigeminal neuropathy developed in 12 patients (5%) and was found to be dependent on the tumor size before treatment. Outpatient gamma knife radiosurgery is a safe and effective treatment method for selected patients with sporadic vestibular schwannomas.

Special indications in gamma knife surgery

Pilocytic astrocytoma (PA) represent a rare indication for Gamma Knife Surgery. Mostly small remnants after surgical debulking are treated. The prognosis depends on specific variants of biological and clinical criteria. In this regard we differentiated two groups of tumors; the so-called 'typical' tumors with a histological grading of WHO Grade I, no prior fractionated radiotherapy and no cystic component and the so called 'atypical' tumors with either a malignant transformation, previous fractionated radiotherapy and/or cystic components. The outcome after GKS was much more favourable for typical PA than for atypical. In typical cases a high tumor control with a very low risk of side effects can be achieved.

Gamma knife radiosurgery for nonfunctioning pituitary adenomas

The efficacy of gamma knife radiosurgery (GKS) for non-functioning pituitary adenomas (NPAs) has been assessed. Sixty patients with NPA were treated by GKS. Complete neurological and endocrinological follow-up information was available for 51 patients. Follow-up examinations included stereotactic magnetic resonance imaging for sequential measurements of the NPA volume. The median dose to the tumor margin was 16.5 Gy (range 11-20 Gy). The mean prescription isodose was 50% (range 45-75%). All patients underwent surgery for NPA before GKS. Fractionated radiotherapy was not applied. Median follow up after GKS was 21,7 months. Actuarial recurrence-free survival was 95% after three years with respect to a single GKS and 100% for patients who underwent repeated GKS. No neurological side effects were detected. Two patients developed new partial pituitary insufficiency after radiosurgery. Postoperative GKS for residual or recurrent small fragments of NPAs is an effective and safe treatment option. The follow-up examination for NPAs should include tumor volumetric analysis.

[Stereotactic radiosurgery using the Gamma Knife for large uveal melanomas]

BACKGROUND

We report the results over 3 years with stereotactic radiosurgery using the Gamma Knife for large and unsuitably located uveal melanomas.

PATIENTS AND METHODS

A total of 100 patients (51 male, 49 female) have been treated since 1997 following a standardised treatment protocol (outpatient single-shot treatment, maximum dose 50 Gy, tumour margin dose min.25 Gy, retrobulbar anaesthesia alone for globe fixation). The localisation and/or dimension of the tumours did not allow radiation brachytherapy with Ru106 plaques. Of the tumours 18 were located in the ciliary body, 61 were located at the posterior pole, and 21 were located in the mid-periphery. All patients were followed and tested ophthalmologically and neuroradiologically at regular intervals. The 1-year follow-up data were available for 73 patients, 2-year follow-up data for 33 patients and 3-year follow-up-data for 17 patients.

RESULTS

Before therapy the maximum apical tumour height (MAH) was median 7.8 mm (95% CI 2.9-12.5 mm): 1 year after treatment (73 patients) the MAH was median 5.7 mm (95% KI 2.4-10.2 mm),2 years after treatment (33 patients) the MAH was median 4.3 mm (95% KI 2.2-8.8 mm),and 3 years after treatment (17 patients) the MAH was median 4.6 mm (95% KI 2.4-8.5 mm). All differences to the MAH of the corresponding patients before treatment were statistically significant (paired t-test). Within the first year after treatment seven patients were enucleated due to a painful secondary glaucoma,within the second year after radiation two patients (one tumour recurrence, and one secondary glaucoma) and within the third year one more patient (tumour recurrence) was enucleated.

CONCLUSIONS

Our 3-year results demonstrate that radiosurgery using the Gamma Knife is beneficial in achieving a local tumour control in 98% of eyes with large and unsuitably located uveal melanomas. The risk for a secondary enucleation is highest in the first year after treatment with a favourable overall rate of 10%. Due to the excellent local tumour control rate we decreased the maximum dose to 40 Gy (min.tumour margin dose 20 Gy) in the subsequently treated patients.

[Ambulatory radiosurgery in cerebral metastatic renal cell carcinoma. 5-year outcome in 58 patients]

Brain metastases (BM) indicate an advanced stage of renal cell cancer (RCC). They pose an increasing challenge to urologists as a result of improved survival due to modern therapy. Median survival of untreated patients with BM who often suffer from neurological deficits is 3 months. Radiosurgery with the Gamma Knife (GK) has increased in use as an alternative to whole brain radiation therapy (WBRT) and/or surgery. This study reports the results of a consecutive series of RCC patients treated for BM by GK radiosurgery during a 5-year period. Between 1994 and 1999, 58 patients with a total of 277 BM and 3.0 (1-19) BM/patient were treated. Because of recurrent BM, 23 (40%) patients received repeated (multiple) GK sessions. The median tumor volume was 3.4 cm3 (0.1-19.1). The median interval between diagnosis of RCC and GK treatment was 2.2 years (0.1-17.2). Symptomatic side effects were detected in 9 (16%) of 58 patients. The median actuarial survival time was 9.9 months. Local tumor control could be achieved in 95% of patients. The GK therapy induced a significant tumor remission accompanied by rapid neurological improvement in 70% of patients. Compared to standard radiotherapy, GK radiosurgery is more effective, less time consuming, and can be repeated. Compared to surgery, radiosurgery is less invasive and better suited to treat multiple metastases in one single session. Surgery and radiosurgery, however, are supplementary methods that are highly effective to control intracerebral metastasizing RCC.

[Stereotaxic precision irradiation of large uveal melanomas with the gamma knife]

BACKGROUND

We report our experience with stereotactic radiosurgery using the Gamma-knife in large uveal melanoma unsuitable for brachytherapy (Ru106).

PATIENTS AND METHODS

We treated 35 patients (16 male, 19 female; age: median 59 years (95% Confidence interval (CI): 31-84 years; 18 right eyes, 17 left eyes). 7 tumors were located juxtapapillary, 16 tumors were located in the mid-periphery and 12 tumors were located in the ciliary body, The localization and/or the dimension of the tumors did not allow for radiation brachytherapy (Ru106). All patients underwent regular clinical, echographical and neuroradiological follow-up examinations.

RESULTS

The follow-up time was median 12 months (95% CI: 4-20 months). A local tumor control defined as either continuous tumor regression or stopping of tumor progression was achieved in 34 (97%) of the 35 treated patients within the observation period. The eye of one patient was enucleated due to tumor regrowth. Maximum apical tumor height according to standardized A-scan before treatment was median 9.1 mm (95% CI: 3.2-13.9 mm) and after treatment median 6.4 mm (95% CI: 2.1 bis 11.9 mm). The difference was statistically highly significant (p < 0.001, one-tailed paired t-test).

CONCLUSIONS

Our results in 35 patients indicate that radiosurgery using the Gamma-knife is beneficial in retaining the eyes of patients with large uveal melanomas that are not suitable for brachytherapy (Ru106).

Stereotactic radiosurgery of large uveal melanomas with the gamma-knife

OBJECTIVE

To present our experience with the Gamma-knife in treating large uveal melanomas with stereotactic radiosurgery.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Fifty-eight patients with unilateral uveal melanomas were treated from 1996 through 1999 with stereotactic radiosurgery using the Gamma-knife. From these we report the results of 35 patients who had a follow-up of more than 1 year after irradiation.

INTERVENTION

Stereotactic radiosurgery with the Gamma-knife.

MAIN OUTCOME MEASURES

Tumor control, maximum apical tumor height, eye retention rate, and visual acuity.

RESULTS

In 34 eyes (97%), local tumor control was achieved. The maximum apical tumor height decreased from a median of 9.1 mm (95% confidence interval [CI], 3.2-13.9 mm) before treatment to 6.2 mm (95% CI, 2.1-11.9 mm) at 1 year after treatment (P<0.001, paired t test). The tumor volume decreased from a median of 0.8 cm(3) before treatment to 0.5 cm(3) 1 year after treatment (P<0.001, paired t test). Two eyes required enucleation (one radiation failure, one secondary glaucoma). The median visual acuity decreased from 20/60 (95% CI, hand movement [HM] to 20/20) before treatment to 20/200 (95% CI, HM to 20/30) at 1 year after treatment (P = 0.001, paired t test).

CONCLUSIONS

Stereotactic radiosurgery using the Gamma-knife is an alternative to enucleation in treating large uveal melanomas. The visual function may be preserved in selected cases.

Gamma Knife radiosurgery of the glomus jugulare tumour - early multicentre experience

Leksell Gamma Knife was used to treat 66 patients with glomus jugulare tumour at 6 European sites between 1992-1998. The age of the patients ranged between 18-80 years (median 54 years). Gamma Knife radiosurgery was a primary treatment in 30 patients (45. 5%). Open surgery preceded radiosurgery in 24 patients (36.4%), embolisation in 14 patients (21.2%) and fractionated radiotherapy in 5 patients (7.6%). The volume of the tumour ranged 0.5-27 cm(3) (median 5,7 cm(3)). The minimal dose to the tumour margin ranged between 10-30 Gy (median 16.5 Gy). After radiosurgery 52 patients were followed, the follow up period was 3-70 months (median 24 months). Neurological deficit improved in 15 patients (29%) and deteriorated in 3 patients (5,8%), one transient and two persistant. Neuroradiological follow up using MRI or CT was performed in 47 patients 4-70 months (median 24 months) after radiosurgery. Tumour size decreased in 19 patients (40%) while in the remaining 28 patients (60%) no change in the tumour volume was observed. None of the tumours increased in volume during the observation period. Control angiography was performed in 6 patients. Pathological vascularisation completely disappeared in one patient, reduced in two and there was no change in the remaining three. Radiosurgery proves to be a safe treatment for glomus jugulare tumour with no mortality and no acute morbidity. Because of its naturally slow growth rate, up to 10 years of follow up will be necessary to establish a cure rate after radiosurgery for these lesions.

Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter

OBJECT

The aim of this retrospective study was to compare treatment results of surgery plus whole-brain radiation therapy (WBRT) with gamma knife radiosurgery alone as the primary treatment for solitary cerebral metastases suitable for radiosurgical treatment.

METHODS

Patients who had a single circumscribed tumor that was 3.5 cm or smaller in diameter were included. Treatment results were compared between microsurgery plus WBRT (52 patients, median tumor dose 50 Gy) and radiosurgery alone (56 patients, median prescribed tumor dose 22 Gy). In case of local/distant tumor recurrence in the radiosurgery group, additional radiosurgical treatment was administered in patients with stable systemic disease. Survival time was analyzed using the Kaplan-Meier method, and prognostic factors were obtained from the Cox model. The patient groups did not differ in terms of age, gender, pretreatment Karnofsky Performance Scale (KPS) score, duration of symptoms, tumor location, histological findings, status of the primary tumor, time to metastasis, and cause of death. Patients who suffered from larger lesions underwent surgery (p < 0.01). The 1-year survival rate (median survival) was 53% (68 weeks) in the surgical group and 43% (35 weeks) in the radiosurgical group (p = 0.19). The 1-year local tumor control rates after surgery and radiosurgery were 75% and 83%, respectively (p = 0.49), and the 1-year neurological death rates in these groups were 37% and 39% (p = 0.8). Shorter overall survival time in the radiosurgery group was related to higher systemic death rates. A pretreatment KPS score of less than 70 was a predictor of unfavorable survival. Perioperative morbidity and mortality rates were 7.7% and 1.6% in the resection group, and 8.9% and 1.2% in the radiosurgery group, respectively. Four patients presented with transient radiogenic complications after radiosurgery.

CONCLUSIONS

Radiosurgery alone can result in local tumor control rates as good as those for surgery plus WBRT in selected patients. Radiosurgery should not be routinely combined with radiotherapy.

[Profile of ambulatory radiosurgery with the gamma knife system. 1: Method and multicenter irradiation concept]

Radiosurgery represents a minimally invasive radiologic method for the treatment of intracranial tumours and arteriovenous malformations. In 1994 the radiosurgical device 'Leksell Gamma Knife' (LGK) was installed in a dedicated logistic environment for outpatient treatments. High quality requirements have to be met for radiosurgery. The target point accuracy taking into account the whole system was shown to be reliably below 0.5 mm whereas the spatial therapeutic resolution was 0.035 cm3. Quality parameters of the dose plan were evaluated for the first 500 consecutive treatments. These values and examples of dose plans were used to emphasize the advantages of the treatment principle with multiple isocenters. An analysis of data in the literature revealed that there is no uniform standard of treatment available in radiosurgery. A highly significant correlation between a risk prediction model for the stereotactic linear accelerator on the one hand and a different model for the LGK on the other could be shown. This result could be helpful in order to proceed towards a more uniform treatment standard in radiosurgery and to improve overall treatment results.

[Profile of ambulatory radiosurgery with the gamma knife system. 2: Report of clinical experiences]

Gamma Knife radiosurgery (GKRS) was applied in 500 consecutive treatments for 445 patients within 2 years. Indications were arterio-venous malformations (93 patients), schwannomas of cranial nerves (75 patients), meningiomas (79 patients; 73 of the tumors involving the skull base), pituitary adenomas (40 patients), craniopharyngiomas (13 cases), gliomas (13 cases), rare indications (12 cases), and brain metastases (126 patients). In arterio-venous malformations two complications were observed whereas two other patients underwent surgery due to intracranial hemorrhage in the latent period after GKRS. In all cases follow-up with MRI showed evidence of an active obliteration process. Out of 24 patients with a follow-up over 1 year, angiography revealed complete obliteration in 9 patients so far. A partial obliteration was evidenced by MRI in 15 cases. In benign tumors (meningiomas and vestibular schwannomas) tumor control rates of 88% and 89% were achieved, respectively. Treatment related side effects were mild and rare; no facial palsy occured after primary Gamma Knife treatment. GKRS was particularly effective in inoperable skull base meningiomas. Cerebral metastases were controlled in 89.5% by a single Gamma Knife treatment. The mean survival period was 11.8 months. In patients receiving a single Gamma Knife treatment the mean survival time was 9.1 months. For patients undergoing multiple (up to 5) sessions of GKRS (because of new tumors) the mean survival period was 17.2 months. MRI showed evidence of adverse radiation reactions in 10/124 patients (8.1%) which were symptomatic in 3 patients (0.8%). The results obtained in patients with cerebral metastases emphasize that GKRS alone is as effective as the combined treatment of these lesions by surgery and fractionated radiotherapy. Our results demonstrated an attractively high therapeutic gain factor of Gamma Knife treatment in key indications of radiosurgery.

The role of high-dose, single-fraction irradiation in small and large intracranial arteriovenous malformations

PURPOSE

Radiosurgery with external beam irradiation is an accepted treatment for small intracranial vascular malformations. It has been proven effective and safe for lesions with volumes of less than 4 cc. However, there is only some limited clinical data for malformations of grade 4 and grade 5, according to Spetzler and Martin.

METHODS AND MATERIALS

At the Heidelberg radiosurgery facility equipped with a linear accelerator, 212 patients with cerebral arteriovenous malformations have been treated since 1984. Thirty-eight percent of the arteriovenous malformations treated were classified inoperable, 14% grade 5, 19% grade 4, and 29% grades 1-3. Radiation doses between 10 and 29 Gy were applied to the 80% isodose contour.

RESULTS

Above a threshold dose of 18 Gy, the overall obliteration rate was 72%. After 3 years, the obliteration rates were 83% with volumes of less than 4.2 cc, 75% with volumes of up to 33.5 cc, and 50% with volumes of up to 113 cc. Of the patients presenting with seizures and paresis, 83% and 56%, respectively, showed improvement, which correlated with the degree of obliteration. After a follow-up period of up to 9 years, the rate of radiation-induced severe late complications was 4.3%. In grade 5 lesions, the risk of side effects was 10%. No serious complications occurred if a maximum dose of less than 25 Gy was applied to treatment volumes of less than 33.5 cc.

CONCLUSION

The success of stereotactic high-dose irradiation of arteriovenous malformations depends on the dose applied. The incidence of radiation-induced side effects increased with the applied dose and treatment volumes. From our experience, doses of less than 25 Gy and treatment volumes of up to 33.5 cc are safe and effective. In the future, new techniques of radiosurgery with linear accelerators and dynamically reshaped beams will allow us to apply homogenous dose distributions. Additional use of magnetic resonance angiography for 3D treatment planning will help to identify the nidus more easily.