Hypofractionated Stereotactic Radiosurgery and Radiotherapy to Large Resection Cavity of Metastatic Brain Tumors

Objective To evaluate the efficacy of postoperative fractionated stereotactic radiosurgery (FSRS) and hypofractionated stereotactic radiotherapy (SRT) to large surgical cavities after gross total resection of brain metastases. Methods A retrospective analysis of 41 patients who had received tumor-bed FSRS (5 fractions) or SRT (10 fractions) after resection of brain metastasis between 2005 and 2015 was performed. All resection cavities were treated with a frameless linear accelerator-based system. Patients who underwent subtotal resection, single-dose SRS to the resection cavity, or were treated with a fractionation schedule other than 5 or 10 fractions, were excluded. Results Twenty-six patients were treated with 5 fractions and 15 patients with 10 fractions. The median planning target volume was 19.78 cm³ (12.3–28 cm³) to the 5-fraction group and 29.79 cm³ (26.3–47.6 cm³) to the 10-fraction group (P = 0.020). The 1-year and 2-year local control rates for all patients were 89.4% and 77.1%, respectively, and 89.6% and 78.6% were free from distant intracranial progression, respectively. No difference was observed in local control or freedom from distant intracranial progression between the 5-fraction or 10-fraction groups. The median overall survival was 28.27 months (95% confidence interval, 19.42–37.12) for all patients. No patient developed necrosis at the resection cavity. Conclusions Fractionation offers the potential to exploit the different biological responses between neoplastic and normal tissues to ionizing radiation. The use of 5 daily doses of 5–6 Gy or 10 daily doses of 3 Gy is a good strategy to have a reasonable local control and avoid neurotoxicity.