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J Neurosurg. 2019 Nov 29:1-9. doi: 10.3171/2019.9.JNS191335. [Epub ahead of print]

Outcomes of stereotactic radiosurgery for pilocytic astrocytoma: an international multiinstitutional study.

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1Department of Radiation Oncology, Cleveland Clinic, Cleveland, Ohio.
13Rose-Ella Burkhardt Brain Tumor and Neuro-Oncology Center, Cleveland, Ohio.
2Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
3Department of Neurosurgery, University of Virginia, Charlottesville, Virginia.
4Department of Functional Neurosurgery and Radiosurgery, Ruber International Hospital, Madrid, Spain.
5Department of Neurosurgery, New York University Langone Medical Center, New York, New York.
6Department of Stereotactic and Radiation Neurosurgery, Na Homolce Hospital, Prague, Czech Republic.
7Division of Neurosurgery, Université de Sherbrooke, Centre de Recherche du CHUS, Sherbrooke, Québec, Canada.
8Department of Neurosurgery, Neurologic Institute, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China.
9Department of Neurosurgery, University of Pennsylvania, Philadelphia, Pennsylvania.
10Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, People's Republic of China.
11Department of Radiation Oncology, Mayo Clinic, Jacksonville, Florida.
12Department of Neurosurgery, University of Louisville, Kentucky; and.



The current standard initial therapy for pilocytic astrocytoma is maximal safe resection. Radiation therapy is considered for residual, recurrent, or unresectable pilocytic astrocytomas. However, the optimal radiation strategy has not yet been established. Here, the authors describe the outcomes of stereotactic radiosurgery (SRS) for pilocytic astrocytoma in a large multiinstitutional cohort.


An institutional review board-approved multiinstitutional database of patients treated with Gamma Knife radiosurgery (GKRS) between 1990 and 2016 was queried. Data were gathered from 9 participating International Radiosurgery Research Foundation (IRRF) centers. Patients with a histological diagnosis of pilocytic astrocytoma treated using a single session of GKRS and with at least 6 months of follow-up were included in the analysis.


A total of 141 patients were analyzed in the study. The median patient age was 14 years (range 2-84 years) at the time of GKRS. The median follow-up was 67.3 months. Thirty-nine percent of patients underwent SRS as the initial therapy, whereas 61% underwent SRS as salvage treatment. The median tumor volume was 3.45 cm3. The tumor location was the brainstem in 30% of cases, with a nonbrainstem location in the remainder. Five- and 10-year overall survival rates at the last follow-up were 95.7% and 92.5%, respectively. Five- and 10-year progression-free survival (PFS) rates were 74.0% and 69.7%, respectively. On univariate analysis, an age < 18 years, tumor volumes < 4.5 cm3, and no prior radiotherapy or chemotherapy were identified as positive prognostic factors for improved PFS. On multivariate analysis, only prior radiotherapy was significant for worse PFS.


This represents the largest study of single-session GKRS for pilocytic astrocytoma to date. Favorable long-term PFS and overall survival were observed with GKRS. Further prospective studies should be performed to evaluate appropriate radiosurgery dosing, timing, and sequencing of treatment along with their impact on toxicity and the quality of life of patients with pilocytic astrocytoma.


GKRS = Gamma Knife radiosurgery; Gamma Knife; PA = pilocytic astrocytoma; PFS = progression-free survival; SRS = stereotactic radiosurgery; oncology; pilocytic astrocytoma; stereotactic radiosurgery


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