Primary Radiosurgery Research Articles

Management of large vestibular schwannoma. Part II. Primary Gamma Knife surgery: radiological and clinical aspects

In large vestibular schwannomas (VSs), microsurgery is the main treatment option. A wait-and-scan policy or radiosurgery are generally not recommended given concerns of further lesion growth or increased mass effect due to transient swelling. Note, however, that some patients do not present with symptomatic mass effect or may still have serviceable hearing. Moreover, others may be old, suffer from severe comorbidity, or refuse any surgery. In this study the authors report the results in patients with large, growing VSs primarily treated with Gamma Knife surgery (GKS), with special attention to volumetric growth, control rate, and symptoms. The authors retrospectively analyzed 33 consecutive patients who underwent GKS for large, growing VSs, which were defined as > 6 cm(3) and at least indenting the brainstem. Patients with neurofibromatosis Type 2 were excluded from analysis, as were patients who had undergone previous treatment. Volume measurements were performed on contrast-enhanced T1-weighted MR images at the time of GKS and during follow-up. Medical charts were analyzed for clinical symptoms. Radiological growth control was achieved in 88% of cases, clinical control (that is, no need for further treatment) in 79% of cases. The median follow-up was 30 months, and the mean VS volume was 8.8 cm(3) (range 6.1-17.7 cm(3)). No major complications occurred, although ventriculoperitoneal shunts were placed in 2 patients. The preservation of serviceable hearing and facial and trigeminal nerve function was achieved in 58%, 91%, and 86% of patients, respectively, with any facial and trigeminal neuropathy being transient. In 92% of the patients presenting with trigeminal hypesthesia before GKS, the condition resolved during follow-up. No patient- or VS-related feature was correlated with growth. Primary GKS for large VSs leads to acceptable radiological growth rates and clinical control rates, with the chance of hearing preservation. Although a higher incidence of clinical control failure and postradiosurgical morbidity is noted, as compared with that for smaller VSs, primary radiosurgery is suitable for a selected group of patients. The absence of symptomatology due to mass effect on the brainstem or cerebellum is essential, as are close clinical and radiological follow-ups, because there is little reserve for growth or swelling.

Stereotactic radiosurgery for convexity meningiomas

Meningiomas of the cerebral convexity are often surgically curable because both the mass and involved dura mater can be removed. Stereotactic radiosurgery has become an important primary or adjuvant treatment for patients with intracranial meningiomas. The authors evaluated clinical and imaging outcomes in patients with convexity meningiomas after radiosurgery. The patient cohort consisted of 125 patients with convexity meningiomas managed using radiosurgery at some point during an 18-year period. The patient series included 76 women, 55 patients who had undergone prior resection, and 6 patients with neurofibromatosis Type 2. Tumors were located in frontal (80 patients), parietal (24 patients), temporal (12 patients), and occipital (9 patients) areas. The WHO tumor grades in patients with prior resections were Grade I in 34 patients, Grade II in 15 patients, and Grade III in 6 patients. Seventy patients underwent primary radiosurgery and therefore had no prior histological tumor diagnosis. The mean tumor volume was 7.6 ml. Radiosurgery was performed using the Leksell Gamma Knife with a mean tumor margin dose of 14.2 Gy. Serial imaging was evaluated in 115 patients (92%). After primary radiosurgery, the tumor control rate was 92%. After adjuvant radiosurgery, the control rate was 97% for Grade I tumors. The actuarial tumor control rates at 3 and 5 years for the entire series were 86.1+/-3.8% and 71.6+/-8.6%, respectively. For patients with benign tumors (Grade I) and those without prior surgery, the actuarial tumor control rate was 95.3+/-2.3% and 85.8+/-9.3%, respectively. Delayed resection after radiosurgery was performed in 9 patients (7%) at an average of 35 months. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 9.6%. Symptomatic peritumoral imaging changes compatible with edema or adverse radiation effects developed in 5%, at a mean of 8 months. Stereotactic radiosurgery provides satisfactory control rates either after resection or as an alternate to resection, particularly for histologically benign meningiomas. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection. Both temporary and permanent morbidity are related to brain location and tumor volume.

STEREOTACTIC RADIOSURGERY FOR RADIATION-INDUCED MENINGIOMAS

Radiation-induced meningiomas of the brain are typically managed with surgical resection. Stereotactic radiosurgery (SRS) has become an important primary or adjuvant management for patients with intracranial meningiomas, but the value of this approach for radiation-induced tumors is unclear. This series consisted of 19 patients (mean age, 40 years) with 24 tumors. The patients met criteria for a radiation-induced meningioma and underwent gamma knife radiosurgery. Seven patients had undergone a previous resection. The World Health Organization tumor grades for those with prior histology were Grade I (n = 5) and Grade II (n = 2). The median tumor volume was 4.4 cm3. Radiosurgery was performed using a median margin dose of 13 Gy. Serial imaging was evaluated in all patients at a median follow-up of 44 months. The control rate was 75% after primary radiosurgery. Delayed resection after radiosurgery was performed in 5 patients (26%) at an average of 39 months. The median latency between radiation therapy for original disease and SRS for radiation-induced meningiomas was 29.7 years (range, 7.3-59.0 years). The overall survival after SRS was 94.1% and 80.7% at 3 and 5 years, respectively. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 5.3% (1 optic neuropathy). Asymptomatic peritumoral imaging changes compatible with an adverse radiation effect developed in 1 patient. SRS provides satisfactory control rates either after resection or as an alternative to resection. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection.

Embolization of Residual Fistula Following Stereotactic Radiosurgery in Cerebral Arteriovenous Malformations

Treatment of brain arteriovenous malformations (BAVMs) often requires a multitechnique approach. We present 2 cases of BAVM, in which initial stereotactic radiosurgery (SRS) was successful in obliterating a significant volume of the nidus. At follow-up angiography, residual fistulas were identified and selectively embolized; this procedure cured the lesions. Many series describe initial embolization to reduce the nidal volume followed by SRS to the remnant. The described cases highlight the value of primary radiosurgery followed by selective fistula embolization.

Repeat radiosurgery for idiopathic trigeminal neuralgia

Although frequently performed, the efficacy and safety of repeat trigeminal neuralgia radiosurgery is not well described. Between August 1997 and December 2002, 19 patients (9 men, 10 women) underwent repeat trigeminal neuralgia radiosurgery. The median interval between procedures was 16 months. The median dose (based on an output factor of 0.87 for the 4-mm collimator) for repeat radiosurgery was 76.1 Gy; the median additive dose was 163.1 Gy. Outcomes were defined as excellent (no pain, no medications), good (no pain, reduced medications), fair (>50% pain reduction), and poor. Median follow-up was 24 months. Outcomes after repeat radiosurgery were excellent (n = 14, 74%), good (n = 1, 5%), fair (n = 3, 16%), and poor (n = 1, 5%). Two patients had recurrent pain at 7 and 22 months; 71% and 61% of patients had an excellent outcome at 1- and 2-years after radiosurgery, respectively. Eleven patients (58%) described facial parathesias (n = 3), numbness (n = 5) or dyesthesias (n = 3). Two patients (11%) developed corneal numbness. Nine of 11 patients (82%) with new trigeminal deficits had excellent outcomes at last follow-up compared with 3 of 8 patients (38%) with unchanged facial sensation (p = 0.07). Repeat trigeminal neuralgia radiosurgery at the dosage described has better facial pain outcomes than primary radiosurgery. However, because the procedure is nonselective and the rate of bothersome numbness was relatively high (16%), dose reduction is recommended to reduce the morbidity of repeat trigeminal neuralgia radiosurgery.

Long term results of radiosurgery for vestibular schwannomas.

Radiosurgery is either a primary or an adjunct management approach used to treat patients with vestibular schwannomas. The goals are long-term tumour growth control, maintenance of cranial nerve function and prevention of new neurologic deficiencies. We sought to determine long-term outcomes measuring the potential benefits against the neurological risks of radiosurgery. 278 patients with vestibular schwannomas underwent Gamma Knife radiosurgery as a treatment modality for from April 1992 to November 2001. The long-term results of 60 patients were evaluated who received radiosurgery as primary treatment. 12 cases presented with previously performed subtotal microsurgical resection or recurrence of disease (12-96 months, median 39). The median treatment volume was 3.8 ccm and the median dose to the tumour margin was 12 Gy. The median patient follow-up time was 88 months (range 72-114 months). Four tumours progressed after primary radiosurgery. Tumour control rate was 93%. Useful hearing (Gardner-Robertson I/II) was preserved in 16 patients (55%). Clinical neurological improvement occurred in 36 patients (60%). Adverse effects comprised neurological symptoms (incomplete facial palsy) (House-Brackman II/III) in five cases (three recovered completely), mild trigeminal neuropathy in three cases, and morphological changes displaying rapid enlargement of preexisting macrocysts in two patients and tumour growth in two other ones. Microsurgical resection was performed in three cases (5%) and one patient underwent a shunting procedure because of hydrocephalus formation. In patients who had undergone previous microsurgery, neither new cranial nerve deficit nor any tumour growth was observed. Radiosurgery performed with current techniques proved to be an effective method for growth control of vestibular schwannomas with both a low mortality rate and a good quality of life. An increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data regarding long-term follow-up are available. It is a post-operative complementary treatment for partially removed tumours. Accordingly, radiosurgery is a useful method for the management of properly selected patients.

Results of γ-Knife Radiosurgery of Brain Arteriovenous Malformations

Between 1992 and 1996 γ-knife radiosurgery was performed on 192 patients with the diagnosis of brain intracerebral arteriovenous malformations (AVM) at Na Homolce Hospital, Prague. The largest diameter of the nidus ranged between 0.6–5.4 cm, median 2.2 cm. The nidus volume ranged 0.15–28.6 cm2, median 3.9 cm2. Thus far, the angiographic evaluation after radiosurgery was performed in 162 patients. The treatment result reference was defined as follows: the interval with a lower limit represented by the percentage of the complete obliteration in the whole group of patients and the upper limit represented by the percentage of the obliteration only in the group of patients with control angiography. The total obliteration of the AVM 1 year after radiosurgery was reached in 18–32% patients, after 2 years in 59–72%, after 3 years in 69–81%, and 4 years after radiosurgery in 71–93% patients. The morbidity of radiosurgery was 6% and, in a majority of the cases, was caused by the postirradiation edema and resolved after corticotherapy. The improvement of secondary epilepsy was observed in 35% of the patients and the improvement of the neurological status in 50%. The mortality of radiosurgical procedure itself was zero. The risk of mortality of the patients with AVM treated with the γ-knife was related to the latent period from treatment until complete obliteration. This period took between 1–3 years when the natural risk of the repeated hemorrhage was the same as that in the nontreated patient. The rebleeding occurred in eight patients; three of them died and five patients were without neurological sequela. If the obliteration did not occur up to 3 years after the γ-knife radiosurgery, reirradiation was indicated. AVM of Spetzler grade I–III proved to have a high rate of obliteration after γ-knife radiosurgery, while only one-third of patients with Spetzler grade IV obliterated after the first radiosurgery. Radiosurgery was not indicated for AVMs Spetzler grade V. AVMs with an average diameter up to 3 cm were good indications for primary radiosurgery as a noninvasive treatment. In AVMs with the average diameter larger than 3 cm, radiosurgery, microsurgery, and embolization are the methods of choice and the radical treatment may require an adequate combination of these methods.

Radiosurgery for brain metastases: Relationship of dose and pattern of enhancement to local control

Purpose : This study aimed to analyze dose, initial pattern of enhancement, and other factors associated with freedom from progression (FFP) of brain metastases after radiosurgery (RS). Methods and Materials : All brain metastases treated with gamma-knife RS at the University of California, San Francisco, from 1991 to 1994 were reviewed. Evaluable lesions were those with follow-up magnetic resonance or computed tomographic imaging. Actuarial FFP was calculated using the Kaplan-Meier method, measuring FFP from the date of RS to the first imaging study showing tumor progression. Controlled lesions were censored at the time of the last imaging study. Multivariate analyses were performed using a stepwise Cox proportional hazards model. Results : Of 261 lesions treated in 119 patients, 219 lesions in 100 patients were evaluable. Major histologies included adenocarcinoma (86 lesions), melanoma (77), renal cell carcinoma (21), and carcinoma not otherwise specified (17). The median prescribed RS dose was 18.5 Gy (range, 10–22) and the media tumor volume was 1.3 ml (range, 0.02–30.9). The initial pattern of contrast enhancement was homogeneous in 68% of lesions, heterogeneous in 12%, and ring-enhancing in 19%. The actuarial FFP was 82% at 6 months and 77% at 1 year for all lesions, and 93 and 90%, respectively, for 145 lesions receiving ≥ 18 Gy. Multivariate analysis showed that longer FFP was significantly associated with higher prescribed RS dose, a homogeneous pattern of contrast enhancement, and a longer interval between primary diagnosis and RS. Adjusted for these factors, adenocarcinomas had longer FFP than melanomas. No significant differences in FFP were noted among lesions undergoing RS for recurrence after prior radiotherapy (119 lesions), RS alone as initial treatment (45), or RS boost (55). Conclusion : A minimum prescribed radiosurgical dose ≥ 18 Gy yields excellent local control of brain metastases. The influence of pattern of enhancement on local control, a new finding in this retrospective analysis, needs to be confirmed.