Feasibility study of applying a RapidPlan model trained with pre-surgical rectal cancer SIBplans to the optimization of post-surgical non-SIB plans.
Abstract: Objective To investigate the feasibility of applying a RapidPlan model trained with pre-surgical rectal cancer simultaneous integrated boost (SIB) plans to the optimization of post-surgical non-SIB plans, and to explore the methods to improve the existing models and extend their applications. Methods An existing RapidPlan model for pre-surgical rectal cancer SIB plans (PTV/PGTV: 41.8 Gy/50.6 Gy) was modified and used to re-optimize 18 clinical post-surgical non-SIB plans among which 7 and 11 cases were prescribed with 45 Gy and 50 Gy to PTV, respectively, without changing the original beam geometries, energies, accelerator configuration and dose volume calculation algorithm. The target structures were matched with PTV and PGTV in the model. The realizable DVH intervals were predicted, and the re-optimized plans were renormalized to achieve similar target coverage of the clinical plans before dosimetric comparison. Results Severe hot spots were caused by matching target areas of non-SIB plans to PTV in the model, while re-optimized plans could achieve similar or better plan quality with smaller standard errors of organs-at-risk dosimetric parameters, compared with the clinical plans. Conclusion RapidPlan model for pre-surgical rectal cancer SIB plans can be applied to the automatic optimization of post-surgical non-SIB plans with higher consistency in plan quality, but the target structure is needed to be matched to the high prescription target structure in SIB model.