Dose-effect relationship of linear accelerator based stereotactic radiotherapy for brain metastases

The purpose of this study is to reveal the dose-effect relationship of linear accelerator (LINAC)-based stereotactic radiotherapy (SRT) in patients with brain metastases (BM).

The PubMed, Cochrane, and Web of Science databases were used to identify studies that reported local tumour control after LINAC-based SRT in patients with BMs. Studies of other approaches that could affect local tumour control, such as whole brain radiotherapy, targeted therapy, and immunotherapy, were excluded from the dose-effect relationship analysis. Data extracted included patient and treatment characteristics and tumour local control. Probit model in XLSTAT 2016 was used for regression analysis, and P < 0.05 was set as the statistically significant level.

After literature screening, 19 eligible studies involving 1523 patients were included in the probit model regression analysis. There was no significant dose-effect relationship between nominal BED₁₀ and peripheral BED₁₀ versus 12-month local control probability. There were significant dose effect relationships between the centre BED₁₀ and the average BED₁₀ versus the 12-month local control probability, with P values of 0.015 and 0.011, respectively. According to the model, the central BED₁₀ and the average BED₁₀ corresponding to probabilities of 90% 12-month local control were 109.2 Gy_BED10 (95% confidence interval (CI): 88.7-245.9 Gy_BED10) and 87.8 Gy_BED10 (95% CI: 74.3-161.5 Gy_BED10), respectively. A 12-month local control rate of 86.9% (95% CI: 81.7-89.7%) and 85.5% (95% CI: 81.2-89.2%) can be expected at a centre BED₁₀ of 80 Gy and an average BED₁₀ of 60 Gy, respectively.

For patients with BM treated with LINAC-based SRT, more attention should be given to the central and average doses of PTV. A clear definition of the dose prescription should be established to ensure the effectiveness and comparability of treatment.