Comparison of 3 vs 5 Fraction Single Isocenter Radiosurgery for Brain Metastases

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• Single isocenter stereotactic radiosurgery (SRS) is an efficient technique for treating multiple brain metastases.
• Fractionated SRS (fSRS) offers various regimens with acceptable outcomes, but direct comparisons are limited.
• Evaluating different fSRS regimens is crucial for optimizing treatment strategies.

Purpose of the Study:

• To compare the efficacy and toxicity of two common fSRS regimens: 9 Gy × 3 fractions and 6 Gy × 5 fractions.
• To assess local tumor control and central nervous system (CNS) toxicity for each fSRS regimen.
• To determine the optimal fSRS regimen for patients with multiple brain metastases.

Main Methods:

• Retrospective review of 1215 brain tumors from 251 patients treated with single isocenter volumetric modulated arc therapy fSRS.
• Exclusion of recurrent tumors and postoperative cavities.
• Analysis of local tumor failure and CTCAE V5.0 CNS grade 3+ toxicity using Kaplan-Meier and Cox regression models.

Main Results:

• Overall 1-year local control was 93%, and 2-year control was 88%.
• The 9 Gy × 3 fractions regimen showed superior 1-year local control (97% vs. 91%, P = .001), especially for tumors <2 cm (99% vs. 95%, P = .004).
• Freedom from grade 3+ toxicity at 1 year was comparable between regimens (99% for 3-fx vs. 96% for 5-fx, P = .097).

Conclusions:

• The 9 Gy × 3 fractions fSRS regimen offers improved tumor control compared to 6 Gy × 5 fractions for brain metastases.
• Toxicity profiles were similar between the two fSRS regimens.
• The 9 Gy × 3 fractions regimen is a potentially preferred option for single isocenter radiosurgery due to enhanced efficiency and local control.