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: PlanFB, PlanAC, and PlanGAT(Respiratory gating). For dosimetric parameters, compared to PlanAC, PlanGAT further significantly reduced liver Dmean, Vd<21.5 Gy, V10Gy; right kidney Dmean; duodenum Dmean, D0.5cc, 1cc, 5cc, 10cc; intestine Dmean, D0.5cc, 5cc, 10cc; stomach Dmean and spinal cord Dmean, V5Gy in group A; however, in Group B, PlanGAT only showed significantly reductions in liver Dmean and duodenum Dmean, D5cc, 10cc. In terms of radiobiology, compared with PlanFB, PlanAC significantly reduced liver NTCP (p = 0.033) in Group B, whereas no difference was observed in Group A (p = 0.231). Additionally, compared to PlanAC, PlanGAT 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, PlanGAT 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.