Dosimetric and radiobiological benefits of patient-specific respiratory motion management for liver tumor stereotactic body radiotherapy

Respiratory motion management was crucial importance in radiotherapy. Our study aimed to explore the dosimetric and radiobiological benefits of various respiratory motion management strategies in liver tumor patients undergoing stereotactic body radiotherapy (SBRT). Respiratory motion images of 23 liver tumor patients were obtained by 4DCT scan under abdominal compression (AC) and free-breathing (FB). Group A included all 23 patients, while group B focused on 11 patients with tumors < 5 cm in diameter. Dosimetric and radiobiological parameters were recorded and compared across three treatment plans for each patient: Plan_FB, Plan_AC, and Plan_{GAT(Respiratory gating)}. For dosimetric parameters, compared to Plan_AC, Plan_GAT further significantly reduced liver D_mean, V_{d<21.5 Gy}, V_10Gy; right kidney D_mean; duodenum D_mean, D_0.5cc, _1cc, _5cc, _10cc; intestine D_mean, D_0.5cc, _5cc, _10cc; stomach D_mean and spinal cord D_mean, V_5Gy in group A; however, in Group B, Plan_GAT only showed significantly reductions in liver D_mean and duodenum D_mean, D_5cc, _10cc. In terms of radiobiology, compared with Plan_FB, Plan_AC significantly reduced liver NTCP (p = 0.033) in Group B, whereas no difference was observed in Group A (p = 0.231). Additionally, compared to Plan_AC, Plan_GAT further reduced liver NTCP (p = 0.001), liver EUD (p < 0.001) and right kidney EUD (p < 0.001) in Group A; however, in Group B, Plan_GAT did not significantly decrease liver NTCP (p = 0.136), indicating that AC offers comparable benefits to GAT. The Pearson's correlations between the reductions in dosimetric and radiobiological parameters and tumor motion or target volume were stronger in Group B than in Group A under AC. So, GAT provides the greatest dosimetric and radiobiological benefits for liver tumors treated with SBRT, while AC offers comparable benefits for liver tumors with < 5 cm in diameter. Thus, given its technical simplicity, AC is recommended for liver tumors < 5 cm in diameter undergoing SBRT.