Single-fraction stereotactic radiosurgery for intracranial targets

Stereotactic radiosurgery (SRS) is a technique for treating intracranial lesions with a high dose of ionizing radiation, usually in a single session, using a stereotactic apparatus for accurate localization and patient immobilization. This article describes several modalities of SRS and some of its applications, particularly for intracranial lesions.     

Optimizing intracranial metastasis detection for stereotactic radiosurgery

BACKGROUND AND PURPOSE: The authors characterize the detection of additional intracranial metastases in cancer patients at the time of stereotactic radiosurgery (SRS) using a specialized high-resolution magnetic resonance imaging (MRI) protocol. METHODS: A retrospective review of 150 consecutive radiosurgical procedures for patients with < or =5 known metastatic intracranial tumors diagnosed using MRI was undertaken at a single center. On the day of SRS, all patients underwent rigid head fixation in a stereotactic frame followed by a specialized MRI using a 3-dimensional fast spoiled-gradient sequence on a 1.5-tesla magnet with double-dose gadolinium. Axial imaging was performed using 2-mm cuts and no gap. RESULTS: Additional metastases were detected in 29.3% of patients. The number of known tumors before SRS was predictive of additional metastases being found (p = 0.014). In multivariate analysis, we more frequently found additional metastases at radiosurgery in patients with 3-5 previously known metastases (p = 0.005), in patients with non-small cell lung cancer (p = 0.012) and in patients with a longer time interval between their diagnostic MRI and their stereotactic MRI (p = 0.030). Age, sex and prior fractionated radiation therapy were not predictive factors. CONCLUSION: Our specialized protocol of high-resolution, double-dose contrast-enhanced MRI is a reliable method to evaluate the extent of intracranial disease in patients with known brain metastasis. Treatment planning for radiosurgery, radiation therapy and open surgical therapy are all impacted by improved metastasis detection.     

Cyst formation after stereotactic radiosurgery for intracranial meningioma

The authors report 2 cases of delayed cyst formation after gamma knife radiosurgery for 3 meningioma lesions. All 3 lesions reported here had a distinctive feature before gamma knife treatment of small and spotty intratumoral cysts. One patient experienced an intriguing clinical course of spontaneous regression of the enlarged cyst, and 2 of the 3 lesions became symptomatic requiring surgical interventions. Cyst formation as a postradiosurgical complication is relatively rare in meningioma patients in the literature, and its pathogenesis is unclear. We describe herein the clinical courses of these 2 patients and review the relevant literature in this report. From our experience of these 2 cases, we suggest that we should be aware of the possible development of spotty intratumoral cysts into larger cysts after stereotactic radiosurgery and that we should carefully observe such patients after the treatment.     

Radiotherapy and stereotactic radiosurgery for pituitary tumors

Based on a review of the literature and our medical center experience, we believe that transphenoidal surgery is the procedure of choice in most patients with pituitary adenomas. Conversely, SRS is a procedure of choice for those with cavernous sinus involvement. Patients with incomplete surgical excision should be considered either for a planned stereotactic treatment or for external beam radiotherapy. The same applies to patients with recurrent tumors. We favor stereotactic treatment in patients who have tumors that are less than 35 mm in diameter and at least 3 mm from the chiasm or optic nerves. Other patients should be considered for three-dimensional conformal radiotherapy. Radiotherapy provides a good treatment alternative in those patients who either refuse surgery or have contraindications to this therapy. Contemporary radiotherapy and SRS for pituitary adenomas is safe and effective treatment. This treatment should be undertaken in medical centers with appropriate expertise and instrumentation.     

Untoward clinical effects after stereotactic radiosurgery for intracranial arteriovenous malformations.

Stereotactic radiosurgery has become one of the most acceptable means of treating deep-seated intracranial arteriovenous malformations, as well as being a useful adjunct in a number of other pathologies. One hundred and sixty patients are discussed, having follow-up of at least 2 years. Radionecrosis occurred in six patients and haemorrhage in the latent period prior to thrombo-obliteration in a further six. Successful thrombo-obliteration was ultimately achieved in 76% of patients. As a bonus, epilepsy was improved in 29 of 48 patients presenting with seizures and worsened transiently in only three of these.     

Stereotactic radiosurgery of intracranial tumors in childhood

The Authors have developed an original stereotactic technique by which the radiation dose erogated by a 4 MV linear accelerator is focused into the target volume with a steep dose gradient at its borders. The technique has been employed in a series of 30 patients affected by deep seated brain tumors and AVMs. The paper deals with the preliminary results obtained in a series of 10 patients in pediatric age.     

Repeat stereotactic radiosurgery for high-grade and large intracranial arteriovenous malformations

BACKGROUND: The treatment of large and high-grade (Spetzler-Martin III-V) AVMs remains a challenge. There is a paucity of literature addressing the efficacy of radiosurgery in this group. We retrospectively analyze our experience with repeat radiosurgery with such AVMs. METHODS: Between 1989 and 2004, 14 patients with large and high-grade AVMs deemed to be nonoperative candidates were treated with repeat radiosurgery. Patients were treated either on a LINAC or gamma knife-based system at 2- to 3-year intervals with targeting of the entire nidus with each treatment. Patients who did not receive their full treatment course or follow-up at the institution were excluded. RESULTS: Mean follow-up was 18 months. The complete obliteration rate was 35.7%, with a mean volume reduction of 53% in the remaining lesions. Twenty percent of grade III and 50% of grade IV lesions experienced cure. Complications included persistent headaches (2 patients). Statistical analysis revealed no difference between obliterated and partially obliterated groups with regard to mean pretreatment volume (24.87 cm(3)), median Spetzler-Martin grade (IV), mean follow-up (30.5 months), total delivered dose (3550 cGy), mean dose per stage (13 Gy), median number of stages (2), or mean interval between treatment stages (40 months). CONCLUSION: The present study demonstrates the potential role of repeat radiosurgery in the treatment of this cohort in the context of our short follow-up. The benefits of repeat therapy could be derived from using lower doses per session and repeat targeting of the lesion in an effort to increase response and decrease complication rates.     

Tumor control after stereotactic radiosurgery in neurofibromatosis patients with bilateral acoustic tumors.

During a 4-year interval, 17 patients with bilateral acoustic tumors (vestibular schwannomas) underwent unilateral stereotactic radiosurgery using a multisource gamma unit; 2 patients underwent radiosurgery of both tumors in separate sessions. Eleven patients with unoperated contralateral tumors served as concurrent controls to compare the effects of radiosurgery with the natural history of acoustic tumors. After radiosurgery, the tumor control and regression rates were 89.5 and 21.1%, respectively (median neuroimaging follow-up, 1.4 years; range, 0.3-3.9). The tumor regression rate increased to 40% for patients evaluated at least 12 months after radiosurgery. In comparison to the unoperated contralateral tumors, stereotactic radiosurgery achieved tumor control, as assessed by the ultimate change in tumor size at follow-up (P, 0.012), the change in tumor size over time (P, 0.006), and tumor growth rates (P, 0.003). This study provided convincing evidence that tumor stabilization after radiosurgery (as assessed by neuroimaging) truly represented tumor control. The incidence of delayed facial neuropathy after radiosurgery compared favorably with the incidence reported after microsurgical removal. Some hearing was preserved in one-third of the patients who had preoperative hearing, including three patients who were contralaterally deaf. Stereotactic radiosurgery should be considered as a primary surgical modality for many patients with neurofibromatosis Type II.     

Long-term results after radiosurgery for benign intracranial tumors

BACKGROUND: Stereotactic radiosurgery is the principal therapeutic alternative to resecting benign intracranial tumors. The goals of radiosurgery are the long-term prevention of tumor growth, the maintenance of patient function, and the prevention of new neurological deficits or adverse radiation effects. Evaluation of long-term outcomes more than 10 years after radiosurgery is needed. METHODS: We evaluated 285 consecutive patients who underwent radiosurgery for benign intracranial tumors between 1987 and 1992. Serial imaging studies were obtained, and clinical evaluations were performed. Our series included 157 patients with vestibular schwannomas, 85 patients with meningiomas, 28 patients with pituitary adenomas, 10 patients with other cranial nerve schwannomas, and 5 patients with craniopharyngiomas. Prior surgical resection had been performed in 44% of these patients, and prior radiotherapy had been administered in 5%. The median follow-up period was 10 years. RESULTS: Overall, 95% of the 285 patients in this series had imaging-defined local tumor control (63% had tumor regression, and 32% had no further tumor growth). The actuarial tumor control rate at 15 years was 93.7%. In 5% of the patients, delayed tumor growth was identified. Resection was performed after radiosurgery in 13 patients (5%). No patient developed a radiation-induced tumor. Eighty-one percent of the patients were still alive at the time of this analysis. Normal facial nerve function was maintained in 95% of patients who had normal function before undergoing treatment for acoustic neuromas. CONCLUSION: Stereotactic radiosurgery provided high rates of tumor growth control, often with tumor regression, and low morbidity rates in patients with benign intracranial tumors when evaluated over the long term. This study supports radiosurgery as a reliable alternative to surgical resection for selected patients with benign intracranial tumors.     

Early results of CyberKnife image-guided robotic stereotactic radiosurgery for treatment of lung tumors.

OBJECTIVE: To determine if image-guided robotic stereotactic radiosurgery (IGR-SRS) by CyberKnife achieves acceptable local control in resectable but medically inoperable patients with non-small cell lung cancer (NSCLC) or pulmonary metastasis, and to evaluate control rates and toxicity. METHODS: Treatment details and outcomes were reviewed for 95 patients (age range 33-96 years) with 136 histologically proven cancers treated by IGR-SRS at the CyberKnife Center of Miami between March 2004 and March 2007. Tumor volumes ranged from 1.2 cc to 338 cc. Targeting was accomplished using combined skeletal alignment and real-time tracking via fiducials placed within the tumor. Total doses ranged from 15 to 67.5 Gy delivered in 1 to 5 fractions. RESULTS: Of the 95 patients treated, 78 (82%) are still alive at 1 to 36 months post-treatment. Nineteen patients have died, four from disease other than cancer progression. All patients but one achieved at least partial response to treatment and tolerated radiosurgery well. For the majority of our patients, fatigue had been the main side effect. CONCLUSIONS: The delivery of precisely targeted high radiation doses with surgical precision to lung tumors in a hypo-fractionated fashion is feasible and safe. Image-guided robotic stereotactic radiosurgery (IGR-SRS) of lung tumors with the CyberKnife achieves excellent rates of local disease control with limited toxicity to surrounding tissues, and in many cases may be curative for patients for whom surgery is not an option.     

Analysis of factors predictive of success or complications in arteriovenous malformation radiosurgery

OBJECTIVE: This study was undertaken to determine which factors were statistically predictive of radiological and clinical outcomes in the radiosurgical treatment of arteriovenous malformations (AVMs). METHODS: The computerized dosimetric and clinical data for 269 patients were reviewed. The AVM nidus was hand-contoured on successive enhanced computed tomographic slices through the nidus, to allow detailed determinations of nidus volume, target miss, normal brain tissue treated, dose conformality, and dose gradient. In addition, a number of patient and treatment factors, including Spetzler-Martin grade, presenting symptoms, dose, number of isocenters, radiological outcome, and clinical outcome, were subjected to multivariate analysis. RESULTS: Two hundred twenty-five patients were treated with radiosurgery for the first time, and 44 patients underwent radiosurgical retreatment. One hundred forty-three patients had AVMs located in or near "eloquent" brain areas and 126 patients did not. Seventy patients demonstrated preoperative neurological findings related to the AVM and 199 did not. Twenty-six patients had previously undergone endovascular treatment and 10 patients had previously undergone surgical treatment of their AVMs. Of the 269 patients studied, 228 experienced no complication, 10 (3.7%) experienced a transient radiation-induced complication, 3 (1%) experienced a permanent radiation-induced complication, and 28 (10%) experienced posttreatment hemorrhage. CONCLUSION: None of the analyzed factors was predictive of hemorrhage after radiosurgery in this study. The 12-Gy volume was predictive of permanent radiation-induced complications. Eloquent AVM location and 12-Gy volume were correlated with the occurrence of transient radiation-induced complications. Better conformality was correlated with a reduced incidence of transient complications. Lower Spetzler-Martin grades, higher doses, and steeper dose gradients were correlated with radiological success.     

Glomus jugulare tumor: tumor control and complications after stereotactic radiosurgery

BACKGROUND: We evaluated toxicity and long-term efficacy of stereotactic radiosurgery in patients with symptomatic or progressive glomus jugulare tumors. METHODS: Twenty-five consecutive patients (age, 30-88 years; 17 women, 8 men) who underwent stereotactic radiosurgery with the Leksell Gamma Knife (dose, 12-18 Gy) were prospectively followed. MRI and clinical examinations were performed at 6 months and 1, 2, and 3 years, and then every 2 years. RESULTS: None of the tumors increased in size, 17 were stable, and 8 decreased (median imaging follow-up, 35 months; range, 10-113 months). Symptoms subsided in 15 patients (60%); vertigo occurred in 1, but balance improved with vestibular training (median clinical follow-up, 37 months; range, 11-118 months). No other new or progressive neuropathy of cranial nerves V-XII developed. CONCLUSIONS: Stereotactic radiosurgery can achieve excellent tumor control with low risk of morbidity in the treatment of glomus jugulare tumors. The lower cranial nerves can safely tolerate a radiosurgical dose of 12 to 18 Gy.     

Short-term tumor control and acute toxicity after stereotactic radiosurgery for glomus jugulare tumors.

OBJECTIVE: Glomus jugulare tumors (GJT) have traditionally been treated by surgery or fractionated external beam radiation therapy (XRT). This study evaluates acute toxicity and short-term efficacy of single-fraction stereotactic radiosurgery (SRS) for the treatment of GJT. STUDY DESIGN AND SETTING: Eight patients (age range 28-74) with GJT underwent SRS (Brainlab linear accelerator) as primary treatment. A nominal dose of 15-16 Gy was prescribed. RESULTS: After undergoing SRS, 7 of 8 patients (87.5%) reported complete resolution of presenting symptoms. Follow-up MRIs showed tumor stabilization in 100% of patients. Transient vertigo occurred in one patient. One patient suffered acute GI upset and transient lower cranial neuropathy. CONCLUSION: Stereotactic radiosurgery is an effective alternative for patients with GJT in achieving tumor control and resolution of symptoms. EBM rating: C-4.     

Place of stereotactic techniques in the modern management of lateral ventricle tumors. Stereotactic biopsies and radiosurgery

The authors make an overview about the use of stereotactic techniques in the management of lateral ventricle tumors. If stereotactic techniques are not in the foreground for the management of lateral ventricle tumors, stereotactic biopsies can be very useful in case of atypical, clinical or radiological presentation of the tumors and radiosurgery can help in case of evolution or re-evolution of tumors after resection. In these cases, stereotactic procedures are very safe. Modern technical evolutions allow the optimization of the stereotactic procedure but also to mix robotic with endoscopic techniques in order to offer new surgical perspectives.