Fractionated stereotactic radiosurgery for malignant gliomas: comparison with single session stereotactic radiosurgery

Purpose Stereotactic radiosurgery (SRS) is feasible for malignant glioma; however, delivering the optimal radiation dose with sufficient large-volume coverage is a major concern. We aimed to investigate the clinical efficacy and safety of fractionated SRS (fSRS) versus single-session SRS (sSRS) for malignant gliomas. Methods We retrospectively reviewed 58 malignant glioma patients who underwent gamma knife SRS from January 2015 to December 2018. Forty-one underwent sSRS, and 17 underwent fSRS. Median dose for fSRS was 28 Gy (range 24-35 Gy), with a median dose of 6 Gy per fraction (range 5-7 Gy). Patients received 4 or 5 fractions on consecutive days. Median dose for sSRS was 18 Gy (range 11-25 Gy), with a median isodose of 50% (range 50-65%). Mean target volumes were 5.9 and 19.3 cc for sSRS and fSRS, respectively (p < 0.001, two-sided t test). Results After SRS, median progression-free survival (PFS) was 4.5 and 4.6 months (p = 0.58), and median overall survival (OS) was 12.7 and 12.6 months for sSRS and fSRS (p = 0.41), respectively (log-rank test). The incidence of clinically significant radiation necrosis was 20.5% (8/39) and 18.8% (3/16) for sSRS and fSRS, respectively (p = 1, Fisher's exact test). Conclusion fSRS for malignant glioma conferred local control and survival comparable with conventional sSRS. The radiation necrosis incidence was comparable between groups when a parallel biological effective dose was administered to the larger target volumes in the fSRS group. fSRS can be a better alternative to sSRS if re-irradiation is considered for large malignant gliomas.