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 contrast-enhanced 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<TRR<0.3 and increased: TRR≤-0.2. Tumor shrinkage effects were compared among 3 groups; near group with a distance of <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.

Keywords: Single-isocenter; brain metastasis; contrast-enhanced magnetic resonance imaging; dynamic conformal arc; lung cancer; stereotactic radiosurgery; tumor quantification.