Clinical outcomes of three-fraction versus five-fraction stereotactic radiosurgery for resected brain metastases

To investigate the clinical outcomes of patients with brain metastases undergoing surgery followed by postoperative three-fraction or five-fraction radiosurgery (SRS) to the resection cavity. Factors associated with local failure and symptomatic radionecrosis were evaluated. One hundred and ninety consecutive patients with 202 brain metastases who received surgery followed by three- or five-fraction SRS to the surgical bed were analyzed. All cavities included in the study received either 27 Gy in 3 fractions or 30 Gy in 5 fractions given daily on consecutive days. Cumulative incidence analysis was used to compare local control and symptomatic radionecrosis between groups from the time of SRS. Ten cavities after 3-fraction and 14 lesions after 5-fraction SRS group recurred (p = 0.38) with a median time to progression of 12 months. Cumulative LC rates were 93% (87–97) and 90.2% (87.5–94.5) at 1 year, and 90% (84–96) and 85.5% (76.2–91.3) at 2 years (p = 0.4) for 3-fraction and 5-fraction SRS groups, respectively. Symptomatic radionecrosis developed in 28 patients (3-fraction SRS,16; 5-fraction SRS,12), requiring surgery or medical treatment; the 1-year and 2-year cumulative rates were 12.8% (8.3–22.4%) and 17.9% (12.3–28.9%), respectively, after 3-fraction SRS, and 9.8% (6.5–19.1%) and 13.0% (7.3–22.2%), respectively, after 5-fraction SRS (p = 0.3). Sixteen patients after 3-fraction and fourteen patients after 5-fraction SRS developed leptomeningeal disease (LMD); 1-year LMD cumulative rates were 13.5% and 13.8%. Both 3 × 9 Gy and 5 × 6 Gy are effective SRS treatment modalities for resected brain metastases associated with high local control and low risk of symptomatic radionecrosis.