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Single- and multi-session radiosurgery for large brain metastases
Zachary A. Seymour, Norbert Kased, David A. Larson, Michael W. McDermott and Penny K. Sneed

Our purpose was to evaluate local control and risk of adverse radiation (ARE) effect after stereotactic radiosurgery (SRS) for large brain metastases (LBM).

Methods: Patients treated 2000-2009 with radiosurgery for LBM, ≥ 8 ml, using stereotactic radiosurgery were retrospectively reviewed for demographics, treatment data, and clinical outcomes.

Results: A total of 212 LBM in 197 patients were treated with SRS. Single-session stereotactic radiosurgery (S-SRS) was used to treat 158 LBM in 146 patients. The median target volume was 10.9 ml with median prescribed dose 16.0 Gy (12.0-18.0 Gy). The remaining 54 LBM in 51 patients were treated with multi-session stereotactic radiosurgery (MS-SRS), most commonly to 25-30 Gy in 5 fractions and median target volume was 16.7 ml. Actuarial local control was 81% at 6 months and 57% at 1 year for S-SRS vs. 59% at 6 months and 27% at 1 year for MS-SRS (p = 0.032 overall; p = 0.51 excluding multi-fraction cases with more than a 2 week interval between MRI and SRS). Risk of ARE at 1 year was 31% for S-SRS vs. 23% for MS-SRS (p = 0.27).

Conclusion: For LBM ≥ 8 ml, LFFP appeared to be comparable for S-SRS and MS-SRS with MRI within 2 weeks of SRS. The MS-SRS dataset was too small to substantiate reduced ARE risk with fractionation.

Keywords: Stereotactic radiosurgery, Stereotactic Body Radiotherapy, Brain metastases, Brain metastasis, Gamma Knife, Cyberknife, Frameless Stereotaxis.

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