Multisession radiosurgery for perioptic meningiomas: medium-to-long term results from a CyberKnife cooperative study

Stereotactic radiosurgery has become an important primary or adjuvant minimally invasive management strategy for patients with intracranial meningiomas with the goals of long-term tumor growth prevention and maintenance of patient neurological function. We evaluated clinical and imaging outcomes of meningiomas stratified by histological tumor grade. The patient cohort consisted of 972 patients with 1045 intracranial meningiomas managed during an 18-year period. The series included 70% women, 49% of whom had undergone a previous resection and 5% of whom had received previous fractionated radiation therapy. Tumor locations included middle fossa (n = 351), posterior fossa (n = 307), convexity (n = 126), anterior fossa (n = 88), parasagittal region (n = 113), or other (n = 115). The overall control rate for patients with benign meningiomas (World Health Organization Grade I) was 93%. In those without previous histological confirmation (n = 482), tumor control was 97%. However, for patients with World Health Organization Grade II and III tumors, tumor control was 50 and 17%, respectively. Delayed resection after radiosurgery was necessary in 51 patients (5%) at a mean of 35 months. After 10 years, Grade 1 tumors were controlled in 91% (n = 53); in those without histology, 95% (n = 22) were controlled. None of the patients developed a radiation-induced tumor. The overall morbidity rate was 7.7%. Symptomatic peritumoral imaging changes developed in 4% of the patients at a mean of 8 months. Stereotactic radiosurgery provided high rates of tumor growth control or regression in patients with benign meningiomas with low risk. This study confirms the role of radiosurgery as an effective management choice for patients with small to medium-sized symptomatic, newly diagnosed or recurrent meningiomas of the brain.

To determine the long-term outcomes and prognostic factors in benign intracranial meningiomas treated with gamma knife stereotactic radiosurgery (GK-SRS). Between 1992 and 2000, 162 patients with benign meningiomas were treated with GK-SRS at the University of Maryland Medical Center. Complete follow-up was available in 137 patients. All patients underwent magnetic resonance imaging (MRI)-based treatment planning. Serial MRIs and clinical exams were performed to assess tumor response. GK-SRS was the primary treatment in 85 patients (62%), whereas 52 patients (48%) had prior surgical resections. The median prescribed dose was 14 Gy (range, 4-25 Gy) to the 50% isodose line. The median tumor volume, treatment volume, and conformity index were 4.5 cc (range, 0.32-80.0 cc), 6.3 cc (range, 1.0-75.2 cc), and 1.34 (range, 0.65-3.16), respectively. The median follow-up for the entire cohort was 4.5 years (range, 0.33-10.5 years). The following factors were included in the statistical analysis for disease-free survival (DFS) and overall survival (OS): sex, age, dose, gross tumor volume (GTV), conformity index (CI), and dural tail coverage. Serial MRI analysis was available in 121 patients (88.3%). Decrease in tumor size was observed in 34 patients (28.1%), whereas there was no change in 77 patients (63.6%), for a crude radiographic control rate of 91.7%. Increase in tumor size was seen in 10 patients (8.3%). New neurologic deficits attributed to the treatment developed in 10 patients (8.3%). The mean DFS and OS for the entire cohort are 4.6 years and 5.0 years, respectively. The 5-year actuarial DFS and OS were 86.2% and 91.0%, respectively. Univariate analysis revealed GTV, sex, CI, and dural tail treatment to be significant prognostic factors. Patients with GTV or =1.4 achieved a longer DFS, with a 5-year DFS of 95.2% vs. 77.3% (p = 0.01). Patients who had the dural tail treated also had higher 5-year DFS (96.0% vs. 77.9%, p = 0.038). Patients with lower conformity (i.e., CI > or =1.4) tended to have the dural tail covered in the prescription isodose line (p = 0.04). The only factor significant in the multivariate analysis was for patients with GTV >10 cc, who had a worse DFS (hazard ratio 4.58, p = 0.05). This report adds to the literature that supports the efficacy and safety of GK-SRS in the management of patients with benign intracranial meningiomas. Our report identified male patients, patients with a CI <1.4, and tumor size greater than 10 cc to have a worse prognosis. Patients who were treated with less conformal plans to cover the dural tail had better outcomes. Our data clearly demonstrate the need to adequately cover the dural tail in patients treated with GK-SRS for benign intracranial meningiomas.

PURPOSE: To describe the design and performance of a novel frameless system for radiosurgery. This technology, called image-guided radiosurgery (IGR), eliminates the need for stereotactic frame fixation by relating the identified lesion to radiographic landmarks. CONCEPT: IGR uses a lightweight x-band linear accelerator, computer-controlled robotic arm (Fanuc manipulator [Fanuc Robotics North America, Inc., Rochester Hills, MI]), paired orthogonal x-ray imagers, and a computer workstation that performs rapid image-to-image registration. During radiosurgery, the x-ray imaging system determines the location of the lesion and communicates these coordinates to the robot, which adjusts the pointing of the linear accelerator beam to maintain alignment with the target. RATIONALE: Existing stereotactic techniques require rigid cranial fixation to establish and maintain a system of reference for targeting. Such frames cause pain for the patient, limit the use of fractionation, and necessitate a prolonged period of general anesthesia if children are to be treated. Furthermore, skeletal or any other type of rigid fixation is difficult to achieve beyond the cranium. IGR was designed to overcome these limitations, which are inherent to nearly all current radiosurgical methods. DISCUSSION: Preliminary testing and early clinical experience have demonstrated the practicality and potential of the IGR concept and have identified the most important directions for improvement. For example, an IGR prototype accurately tracked target displacements in three dimensions but showed reduced accuracy when confronted by rotational movements. This observation led to development of a new generation of tracking algorithm that promises to improve tracking in all six dimensions. Further experience indicated that improvements in the quality of the x-ray images were needed to allow the system to locate and treat target sites outside the cranium. Consequently, a new x-ray imaging technology with superior resolution and increased sensitivity has been added to the system. These improvements should make it possible to apply IGR techniques to a variety of targets located throughout the body. This article describes and critiques the components of the IGR and summarizes our preliminary clinical experience.