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