Effective control of brain metastases irrespective of distance from isocenter in single-isocenter multitarget stereotactic radiosurgery

Abstract

Background/Aim: Few previous studies have evaluated the effectiveness of single-isocenter multitarget (SIMT) stereotactic radiosurgery (SRS) in clinical practice. Patients and Methods: Gross tumor volumes of 113 metastases in 13 patients were measured by contrastenhanced magnetic resonance imaging. Prescribed doses were set at 20-24 Gy. Based on tumor reduction rates (TRRs) measured before and after SIMT SRS, tumor shrinkage effect was categorized into four grades; almost disappeared: TRR=1, decreased: 0.3≤TRR<1, stable:-0.2 <3.2 cm, middle group with a distance of ≥3.2 cm and <6.4 cm, and far group with a distance of ≥6.4 cm, categorized by distance from the isocenter. Results: Median survival time was 17 months, with 63.7%, 11.5% and 12.4% of metastases corresponded to almost disappeared, decreased and stable, respectively. No significant difference was found in the distribution for TRRs among 3 groups. Conclusion: Good local control of multiple brain metastases was demonstrated by SIMT SRS, irrespective of distance from the isocenter.