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Purpose
To describe the use of radiosurgery (RS) alone to the resection cavity after resection of brain metastases as an alternative to adjuvant whole-brain radiotherapy (WBRT).
Methods and Materials
Sixty-two patients with 64 cavities were treated with linear accelerator-based RS alone to the resection cavity after surgical removal of brain metastases between March 2007 and August 2010. Fifty-two patients (81 % ) had a gross total resection. Median cavity volume was 8.5 cm3. Forty-four patients (71 % ) had a single metastasis. Median marginal and maximum doses were 18 Gy and 20.4 Gy, respectively. Sixty-one cavities (95 % ) had gross tumor volume to planning target volume expansion of ? mm.
Results
Six-month and 1-year actuarial local recurrence rates were 14 % and 22 % , respectively, with a median follow-up period of 9.7 months. Six-month and 1-year actuarial distant brain recurrence, total intracranial recurrence, and freedom from WBRT rates were 31 % and 51 % , 41 % and 63 % , and 91 % and 74 % , respectively. The symptomatic cavity radiation necrosis rate was 8 % , with 2 patients (3 % ) undergoing surgery. Of the 11 local failures, 8 were in-field, 1 was marginal, and 2 were both (defined as in-field if ?0 % of recurrence within the prescription isodose and marginal if ?0 % outside of the prescription isodose).
Conclusions
The high rate of in-field cavity failure suggests that geographic misses with highly conformal RS are not a major contributor to local recurrence. The current dosing regimen derived from Radiation Therapy Oncology Group protocol 90-05 should be optimized in this patient population before any direct comparison with WBRT.
