J. Zhang1, W. Wang2, J. You3, S. Qian4, J. Wang1, and S. Jiang1; 1Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin; Tianjin, Chi, Tiajin, Tianjin, China, 2Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin, China, 3Department of Radiation oncology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention Therapy, Tianjin, China, 4Department of Medical Imaging, The 960th Hospital of Joint Logistics Support Force of PLA, jinan, Shandong, China
Purpose/Objective(s): VMAT plans for breast cancer have been proved to be able to reduce the dose to organs at risk (OAR) while ensuring the dose to the target volume. However, the complexity and variability of target volumes in postoperative breast cancer patients and more OAR optimization objective parameters will further increase the difficulty of radiation oncologists and physicists. The aim of this study was to explore the clinical implementation of an integrated Automatic contouring and Automatic VMAT planning workflow for postoperative breast cancer radiotherapy. Materials/
Methods: Data from thirty-eight breast cancer patients were retrospectively analyzed, including ten left-side postmastectomy patients (Group ¢ñ) and ten right-side postmastectomy patients (Group ¢ò) with prescribed dose of 50 Gy in 25 fractions, ten patients with left-side breast-conserving surgery (Group ¢ó), eight patients with right-side breast-conserving surgery (Group ¢ô) with hypofractionated prescribed dose of 42.56 Gy in 16 fractions. The clinical target volume (CTV) and OAR were delineated using automatic contouring. The OAR of each group included esophagus, trachea, larynx, thyroid, contralateral breast, ipsilateral humerus, head, coronary arteries, stomach and liver. Both Auto-VMAT and Manual-VMAT treatment plans were optimized. Each VMAT plan was set with two partial arcs in clockwise rotation. The angles of the gantry ranged from 294 ¡ã to 156 ¡ã for left side, while 204¡ã to 66¡ã for the right side. Results: The segmentation result of automatic delineation about CTV and OAR exhibited excellent agreement by radiation oncologists, including patients with expander or implant reconstructions, and reduced time for contouring from 40 min to 10 min. The optimizing and running time (Auto-VMAT vs. Manual-VMAT) was decreased by 41 min in Group ¢ñ, 42 min in Group ¢ò, 48 min in Group ¢ó, 48 min in Group ¢ô. The performance of Auto-VMAT was equivalent or better than the plans designed by Manual-VMAT. Dose coverage for PTV was similar within both VMAT plans. The homogeneity and conformal index (HI and CI) of PTV were improved in Auto-VMAT vs. Manual-VMAT comparisons. Specifically, HI of four patient groups were 1.09 vs. 1.11, 1.11 vs. 1.13, 1.09 vs. 1.12, 1.09 vs. 1.11, CI of four groups were 0.91vs.1.05, 0.86 vs. 0.83, 0.91 vs. 0.87, 0.89 vs. 0.88. Among the seventy OAR parameters, fifty-eight (83%, 58/70) parameters of Auto-VMAT showed lower doses compared with those of Manual-VMAT. Moreover, the Auto-VMAT provided significant reduced doses for ipsilateral lung, contralateral lung, heart and coronary artery. Conclusion: The combination of Automatic Contouring system and Automatic VMAT planning could potentially realize automatic operation in the process of radiotherapy, and the planning workflow could be applied in multi-site, multi-prescription of breast cancer with considerable clinical implementation value.
