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Hideyuki Kano, Douglas Kondziolka, John C. Flickinger, Huai-che Yang, Thomas J. Flannery, Nasir R. Awan, Ajay Niranjan, Josef Novotny Jr., and L. Dade Lunsford

Object

The authors conducted a study to define the long-term outcomes and risks of stereotactic radiosurgery (SRS) for pediatric arteriovenous malformations (AVMs).

Methods

Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs; 135 patients were younger than 18 years of age. The median maximum diameter and target volumes were 2.0 cm (range 0.6–5.2 cm) and 2.5 cm3 (range 0.1–17.5 cm3), respectively. The median margin dose was 20 Gy (range 15–25 Gy).

Results

The actuarial rates of total obliteration documented by angiography or MR imaging at 71.3 months (range 6–264 months) were 45%, 64%, 67%, and 72% at 3, 4, 5, and 10 years, respectively. The median time to complete angiographically documented obliteration was 48.9 months. Of 81 patients with 4 or more years of follow-up, 57 patients (70%) had total obliteration documented by angiography. Factors associated with a higher rate of documented AVM obliteration were smaller AVM target volume, smaller maximum diameter, and larger margin dose. In 8 patients (6%) a hemorrhage occurred during the latency interval, and 1 patient died. The rates of AVM hemorrhage after SRS were 0%, 1.6%, 2.4%, 5.5%, and 10.0% at 1, 2, 3, 5, and 10 years, respectively. The overall annual hemorrhage rate was 1.8%. Larger volume AVMs were associated with a significantly higher risk of hemorrhage after SRS. Permanent neurological deficits due to adverse radiation effects developed in 2 patients (1.5%) after SRS, and in 1 patient (0.7%) delayed cyst formation occurred.

Conclusions

Stereotactic radiosurgery is a gradually effective and relatively safe management option for pediatric patients in whom surgery is considered to pose excessive risks. Although hemorrhage after AVM obliteration did not occur in the present series, patients remain at risk during the latency interval until obliteration is complete. The best candidates for SRS are pediatric patients with smaller volume AVMs located in critical brain regions.

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Hideyuki Kano, Huai-che Yang, Douglas Kondziolka, Ajay Niranjan, Yoshio Arai, John C. Flickinger, and L. Dade Lunsford

Object

To evaluate the role of stereotactic radiosurgery (SRS) in patients with recurrent or residual intracranial ependymomas after resection and fractionated radiation therapy (RT), the authors assessed overall survival, distant tumor relapse, progression-free survival (PFS), and complications.

Methods

The authors retrospectively reviewed the records of 21 children with ependymomas who underwent SRS for 32 tumors. There were 17 boys and 4 girls with a median age of 6.9 years (range 2.9–17.2 years) in the patient population. All patients underwent resection of an ependymoma followed by cranial or neuraxis (if spinal metastases was confirmed) RT. Eleven patients had adjuvant chemotherapy. Twelve patients had low-grade ependymomas (17 tumors), and 9 patients had anaplastic ependymomas (15 tumors). The median radiosurgical target volume was 2.2 cm3 (range 0.1–21.4 cm3), and the median dose to the tumor margin was 15 Gy (range 9–22 Gy).

Results

Follow-up imaging demonstrated therapeutic control in 23 (72%) of 32 tumors at a mean follow-up period of 27.6 months (range 6.1–72.8 months). Progression-free survival after the initial SRS was 78.4%, 55.5%, and 41.6% at 1, 2, and 3 years, respectively. Factors associated with a longer PFS included patients without spinal metastases (p = 0.033) and tumor volumes < 2.2 cm3 (median tumor volume 2.2 cm3, p = 0.029). An interval ≥18 months between RT and SRS was also associated with longer survival (p = 0.035). The distant tumor relapse rate despite RT and SRS was 33.6%, 41.0%, and 80.3% at 1, 2, and 3 years, respectively. Factors associated with a higher rate of distant tumor relapse included patients who had spinal metastases before RT (p = 0.037), a fourth ventricle tumor location (p = 0.002), and an RT to SRS interval < 18 months (p = 0.015). The median survival after SRS was 27.6 months (95% CI 19.33–35.87 months). Overall survival after SRS was 85.2%, 53.2%, and 23.0% at 1, 2, and 3 years, respectively. Adverse radiation effects developed in 2 patients (9.5%).

Conclusions

Stereotactic radiosurgery offers an additional option beyond repeat surgery or RT in pediatric patients with residual or recurrent ependymomas after initial management. Patients with smaller-volume tumors and a later recurrence responded best to radiosurgery.

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Thomas Flannery, Hideyuki Kano, Juan J. Martin, Ajay Niranjan, John C. Flickinger, L. Dade Lunsford, and Douglas Kondziolka

Object

The aim in this study was to determine the outcomes of boost stereotactic radiosurgery, specifically Gamma Knife surgery (GKS), for recurrent primitive neuroectodermal tumors (PNETs) in children in whom initial multimodality management had failed.

Methods

The authors performed a retrospective analysis of 7 patients who underwent a total of 15 GKS procedures for locally recurrent or metastatic PNETs. Nine procedures were directed at the primary site, whereas 6 were directed at distant brain sites. All patients received multimodality therapy, including resection, fractionated radiotherapy, and chemotherapy. The mean interval from diagnosis to first stereotactic radiosurgery was 25.8 months (range 11–35 months). The mean tumor volume was 3.9 cm3 (range 1.1–13.1 cm3), and an average marginal dose of 14.5 Gy (range 9–20 Gy) was administered.

Results

Following salvage GKS, 2 patients had early disease progression (median survival of 5 months after GKS). Five patients had late disease progression (complete response in 3, partial response in 1, and stable disease in 1) and a median survival of 30 months after GKS. Four of the 5 patients who had late progression underwent repeat GKS for marginal recurrence. No adverse radiation effects were observed in these 7 patients.

Conclusions

The GKS modality was a well-tolerated and useful boost strategy in pediatric patients with PNET and a poor prognosis in whom initial multimodality management had failed. However, local or distant disease progression or diffuse leptomeningeal spread ultimately proved fatal to these patients.