Gamma knife stereotactic radiosurgery for brainstem Metastasis: The University of Pennsylvania Experience

Michelle Alonso-Basanta1, Lara P. Bonner Millar2, Denise Miller3, James Kolker2, Jay F. Dorsey2, John Y.K. Lee3

1Philadelphia, United States 2Department of Radiation Oncology, University of Pennsylvania 3Department of Neurosurgery, University of Pennsylvania

Keywords: brain metastasis, brain stem, gamma knife, radiosurgery, outcome

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     Brainstem metastases are often unresectable but produce significant neurological symptoms and have an unfavorable prognosis. Previous studies have shown stereotactic radiosurgery (SRS) provides intracranial local control, but the potential for morbidity to the brainstem has excluded brainstem metastases from multiple clinical trials.
     We evaluated our clinical outcomes for brainstem metastases after radiosurgery.
     The median age at of our 40 patients at the time of GK-SRS was 59.7 years old. 25 (63%) cases were male and 15 (37%) were female.
     We retrospectively reviewed our experience of treating brainstem metastases with Gamma Knife stereotactic radiosurgery (GK-SRS) at Pennsylvania Hospital from 2006-2010. A total of 40 patients were identified from the 518 cases of brain metastases treated with GK-SRS.
       The most frequent primary tumor types were lung (43%, n=17) and melanoma (23%, n=9). Twenty of the cases had metastasis to pons, 4 to the medulla, 2 to the cerebellopontine angle, and 16 to the midbrain/thalamus region. At the time of the treatment, there were 7 cases of single brainstem metastasis. Twenty-one (55%) had 1-3 concurrent brain parenchymal metastases, 15 (39%) had 4-10 brain metastasis, and 2 (5%) had >10 brain metastasis that were treated with GK-SRS. Nineteen cases (48%) received whole brain radiotherapy (WBRT) prior to GK-SRS, and 7 cases (18%) received WBRT after GK-SRS. Fifteen cases (38%) received GK-SRS only. The median the prescribed dose was 16 Gy (range: 12-24 Gy). At the time of analysis, the average length of follow-up was 8.6 months (range 1-45 months). There were 33 cases (82.5%) with radiological imaging follow up. Sixty-one percent (20/33) of the lesions had no radiological progression at the treated site after GK-SRS. Three patients (9%) had radiographic evidence of radiation necrosis within the treated brainstem lesion, two of which were symptomatic.
     This was a retrospective study.
     GK-SRS offers an alternative treatment options for unresectable brainstem metastasis.
     Our experience shows that GK-SRS is effective for local control, and is a reasonable treatment option for patients with brainstem metastasis.


Project Roles:

M. Alonso-Basanta (), L. Millar (), D. Miller (), J. Kolker (), J. Dorsey (), J. Lee ()