Investigation of Dosimetric Evaluation and Treatment Planning Time of Inverse Planning Optimization in Combined Intracavitary and Interstitial Brachytherapy for Cervical Cancer

Clinical evidence demonstrating the effectiveness of optimization and efficiency of treatment plan is limited because the Inverse planning optimization of source position and dwell time variations is complex. Our purpose was to investigate the comparison of the dosimetric evaluations and treatment planning time in two inverse planning algorithms with the conventional Manchester treatment planning for cervical cancer brachytherapy. We retrospectively identified 14 patients who underwent manually and inversely optimized treatment plans using inverse planning simulated annealing (IPSA) and hybrid inverse planning optimization (HIPO). The analysis was performed to analyze the effects of various factors on the dosimetric evaluation indices, such as the D90 for the high-risk clinical target volume (HR-CTV) and D2cc of the organ at risk (OAR), and the distribution of dwell time and optimization time in each algorithm. In most plans, D90 of the HR-CTV exceeded 7 Gy, and the D2cc of the OARs, on average, was below the tolerance dose for all plans. However, the HR-CTV D90 and D2cc of the IPSA-optimized treatment plan tended to be smaller than those of the other plans when the dwell time deviation constraint value of the optimization parameters was increased. The treatment plans used in the Manchester method and those obtained by IPSA and HIPO have similar dose distributions and dose volume histogram parameters. Moreover, the time required to create a treatment plan was reduced by the IPSA and HIPO. Also, it was suggested that IPSA may result in extreme source dwell positions and dwell times.