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 (Dmax: standardized mean difference (SMD) = -0.14, 95% confidence interval (CI): −0.61 to 0.32; Dmean: 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 (Dmax) to the heart and liver (heart Dmax: SMD = -1.53, 95% CI: −2.53 to −0.52, p = 0.003; liver Dmax: SMD = -1.33, 95% CI: −2.29 to −0.37, p = 0.007). Subgroup analysis revealed that DLM-linac significantly reduced Dmax to the eyes and esophagus compared to C-arm linacs (eyes Dmax: SMD = -0.62, 95% CI: −1.22 to −0.01, p = 0.045; esophagus, Dmax: 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.