To evaluate the clinical outcomes with linear accelerator-based multidose stereotactic radiosurgery (SRS) to large postoperative resection cavities in patients with large brain metastases.

Between March 2005 to May 2012, 101 patients with a single brain metastasis were treated with surgery and multidose SRS (9 Gy × 3) for large resection cavities (>3 cm). The target volume was the resection cavity with the inclusion of a 2-mm margin. The median cavity volume was 17.5 cm(3) (range, 12.6-35.7 cm(3)). The primary endpoint was local control. Secondary endpoints were survival and distant failure rates, cause of death, performance measurements, and toxicity of treatment.

With a median follow-up of 16 months (range, 6-44 months), the 1-year and 2-year actuarial survival rates were 69% and 34%, respectively. The 1-year and 2-year local control rates were 93% and 84%, with respective incidences of new distant brain metastases of 50% and 66%. Local control was similar for radiosensitive (non-small cell lung cancer and breast cancer) and radioresistant (melanoma and renal cell cancer) brain metastases. On multivariate Cox analysis stable extracranial disease, breast cancer histology, and Karnofsky performance status >70 were associated with significant survival benefit. Brain radionecrosis occurred in 9 patients (9%), being symptomatic in 5 patients (5%).

Adjuvant multidose SRS to resection cavity represents an effective treatment option that achieves excellent local control and defers the use of whole-brain radiation therapy in selected patients with large brain metastases.