Postoperative Stereotactic Radiation Therapy for Patients With Resected Brain Metastases: Clinical Outcomes and Comparing the Efficacy of Single-Fraction Radiosurgery and Fractionated Stereotactic Radiation Therapy

Abstract

To investigate clinical outcomes and compare the efficacy of post-operative single-fraction stereotactic radiosurgery (SRS) versus fractionated stereotactic radiation therapy (fSRT) delivered to the cavity of resected brain metastases. A prospective database of all patients with resected brain metastases treated with postoperative SRS or fractionated stereotactic radiation therapy (fSRT) from 2011 to 2016 was reviewed. Chi-squared and the Kruskal-Wallis tests were performed to compare treatment groups. Survival outcomes were estimated using the Kaplan-Meier method. Cox proportional hazards models were used to identify predictors of local failure (LF) and distant brain failure (DBF), and the log-rank test was used to compare outcomes between treatment groups. There were 79 resected lesions evaluated in 73 patients, with a median pre-operative tumor diameter of 33 mm (range 9-83 mm), median cavity volume at treatment planning of 8131.4 mm3 (range 655.04-53006.3 mm3), and no patients receiving prior whole-brain radiation therapy. Single-fraction SRS (median peripheral dose 15 Gy, range 14-20 Gy) was used to treat 49 lesions (62%) and 30 lesions (38%) received fSRT (median peripheral dose 23 Gy, range 18-30 Gy, delivered in a median of 3 fractions, range 2-5 fractions). Resected lesions receiving fSRT had larger preoperative tumor diameters (median 38mm vs 31mm, p = 0.050) and resection cavity volumes (median 12175.2 mm3 vs 5802.5mm3, p <0.0001). The median overall survival (OS) for the cohort was 8.6 (range 0.1-40.9) months. Actuarial rates of local control for the overall cohort were 94.2% at 6 months and 80.7% at 12 months with a median follow-up of 6.8 months after SRS. Tumor diameter was significantly associated with LF (HR 1.04, CI 1.008 -1.074). Melanoma histology (HR 3.027, CI 1.415-6.477) and ≥ 4 lesions at presentation (HR 3.153, CI 1.399- 7.105) were significantly associated with DBF. Local control at 12 months for resected lesions receiving SRS and fSRT was 81.2% and 80.2% respectively (p =0.651). Both treatments were tolerated well with 3 lesions (6.1%) receiving SRS developing radionecrosis (RN) and 1 lesions (3.3%) receiving fSRT developing RN. Our results suggest post-operative fSRT delivered to resection cavities is well tolerated and can achieve similar rates of local control compared to single-fraction SRS, while treating significantly larger lesions and resection cavities. Post-operative fSRT should be considered for selected patients with larger cavities from resected brain metastases.