A meta-analysis of dose-volume parameters and treatment efficiency comparing O-ring and C-arm accelerator systems for craniospinal irradiations

Background and Purpose Craniospinal irradiation (CSI) is a critical treatment modality for central nervous system (CNS) tumors. This study aimed to compare the dose-volume parameters and treatment efficiency between O-ring and C-arm linear accelerators (linacs) for CSI. Materials and Methods A systematic search of English and Chinese databases was conducted from January 2005 to January 2026. Studies were evaluated using the PICOS framework. Data extraction and meta -analysis were performed using Stata 18.0 software encompassing subgroup analysis. Results Twelve studies involving 87 patients were included. No significant differences were found in dose to the planning target volume (PTV) between O-ring and C-arm linacs (D max : standardized mean difference (SMD) = -0.14, 95% confidence interval (CI): −0.61 to 0.32; D mean : SMD=−0.53, 95% CI: −1.57 to 0.50). However, O-ring linacs, including dual-layer multi-leaf collimator linacs (DLM-linac) and helical radiotherapy (HR), delivered significantly lower maximum doses (D max ) to the heart and liver (heart D max : SMD = -1.53, 95% CI: −2.53 to −0.52, p = 0.003; liver D max : SMD = -1.33, 95% CI: −2.29 to −0.37, p = 0.007). Subgroup analysis revealed that DLM-linac significantly reduced D max to the eyes and esophagus compared to C-arm linacs (eyes D max : SMD = -0.62, 95% CI: −1.22 to −0.01, p = 0.045; esophagus, D max : SMD = -0.45, 95% CI: −0.89 to −0.01, p = 0.044). Additionally, HR had the highest monitor units and the longest treatment time among all linac types. Conclusions Both O-ring and C-arm linacs are effective for CSI. No significant difference in PTV dose was revealed when the doses to the lungs and thyroid are comparable. However, O-ring linacs, particularly DLM-linac, provide superior protection for critical organs such as eyes and esophagus without extending treatment time. Considering both dose advantage and treatment efficiency, DLM-linac is a suitable radiotherapy treatment modality for CSI.