Standard Dose Versus Reduced Dose Single Fraction Preoperative Radiosurgery for Resected Brain Metastases (PROPS-BM) International Multicenter Cohort Study.

PURPOSE

Single fraction preoperative stereotactic radiosurgery (SRS) has historically used a 10% to 20% dose reduction standard dosing. However, the effects of this dose reduction are not well characterized. The goal of this study was to compare outcomes and toxicity of standard dose (SD) with reduced dose (RD) single fraction preoperative SRS.

METHODS AND MATERIALS

Patients with brain metastases from solid cancers, of which at least 1 lesion measuring ≤ 4 cm was treated with single fraction preoperative SRS and underwent planned resection were included from the Preoperative Radiosurgery for Brain Metastases (PROPS-BM international multicenter combined prospective and retrospective registries from 8 institutions. SD was a priori defined as ≥20 Gy for lesions ≤2 cm, ≥17 Gy for >2 to 3 cm, and ≥14 Gy for >3 to 4 cm based on institutional dosing practices. Multivariable and propensity score matched analyses were performed.

RESULTS

The cohort consisted of 307 patients with 307 preoperative SRS treated index lesions. SD was used in 124 patients (40%) and RD was used in 183 patients (60%). Median dose for lesions 0 to 2 cm (n = 73), >2 to 3 cm (n = 152), and >3 to 4 cm (n = 82) was 20, 18, and 15 Gy in the SD cohort and 16, 15, and 13 Gy in the RD cohort, respectively. There was no difference in 2-year cavity local recurrence (LR, 16% vs 15%, = .69), adverse radiation effect (ARE, 8% vs 6%, = .77), meningeal disease (2% vs 8%, = .07), composite endpoint of cavity LR, ARE, or nodular meningeal disease (23% vs 22%, = .86), or overall survival (49% vs 36%, = .15). Results were similar within each specific lesion diameter subgroup and within the propensity score matched cohorts (n = 168).

CONCLUSIONS

Both SD and RD single fraction preoperative SRS demonstrate excellent rates of cavity LR and ARE. Cavity LR risk increased with larger lesion size, regardless of SRS dose category. There does not seem to be an advantage in efficacy or toxicity for RD over SD single fraction preoperative SRS. Additional studies are warranted to optimize preoperative SRS dose and fractionation.