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

PURPOSE: 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. PATIENTS AND METHODS: 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. RESULTS: 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%. CONCLUSIONS: 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.