Advantages and robustness of partial VMAT with prone position for neoadjuvant rectal cancer evaluated by CBCT-based offline adaptive radiotherapy

• Published in: Radiation oncology (London, England) England), 2023-06, Vol.18 (1), p.102-102, Article 102
• Main Authors: Zhang, Zhe, Yu, Shou, Peng, Feng, Tan, Zhibo, Zhang, Lei, Li, Daming, Yang, Pengfei, Peng, Zhaoming, Li, Xin, Fang, Chunfeng, Wang, Yuenan, Liu, Yajie
• Format: Article
• Language: English
• Subjects: Algorithms; Analysis; Bladder; Cancer; Cancer therapies; Care and treatment; Colorectal cancer; Complications; Computed tomography; CT imaging; Development and progression; Dosimeters; Dosimetry; Formability; Health aspects; Humans; Image registration; Intestine; Lymphatic system; Medical imaging; Mesentery; Neoadjuvant rectal cancer; Neoadjuvant Therapy; Offline ART; Optimization; Partial VMAT; Patient outcomes; Patients; Planning; Prone Position; Radiation dosimetry; Radiation therapy; Radiotherapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Intensity-Modulated - methods; Rectal Neoplasms - diagnostic imaging; Rectal Neoplasms - radiotherapy; Rectum; Registration; Retrospective Studies; Robustness; Side effects; Software; Spiral Cone-Beam Computed Tomography; Tomography; Toxicity; Ultrasonic imaging
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/s13014-023-02285-6

This study aims to explore the advantages and robustness of the partial arc combined with prone position planning technique for radiotherapy in rectal cancer patients. Adaptive radiotherapy is recalculated and accumulated on the synthesis CT (sCT) obtained by deformable image registration between planning CT and cone beam CT (CBCT). Full and partial volume modulation arc therapy (VMAT) with the prone position on gastrointestinal and urogenital toxicity, based on the probability of normal tissue complications (NTCP) model in rectal cancer patients were evaluated. Thirty-one patients were studied retrospectively. The contours of different structures were outlined in 155 CBCT images. First, full VMAT (F-VMAT) and partial VMAT (P-VMAT) planning techniques were designed and calculated using the same optimization constraints for each individual patient. The Acuros XB (AXB) algorithm was used in order to generate more realistic dose distributions and DVH, considering the air cavities. Second, the Velocity 4.0 software was used to fuse the planning CT and CBCT to obtain the sCT. Then, the AXB algorithm was used in the Eclipse 15.6 software to conduct re-calculation based on the sCT to obtain the corresponding dose. Furthermore, the NTCP model was used to analyze its radiobiological side effects on the bladder and the bowel bag. With a CTV coverage of 98%, when compared with F-VMAT, P-VMAT with the prone position technique can effectively reduce the mean dose of the bladder and the bowel bag. The NTCP model showed that the P-VMAT combined with the prone planning technique resulted in a significantly lower complication probability of the bladder (1.88 ± 2.08 vs 1.62 ± 1.41, P = 0.041) and the bowel bag (1.28 ± 1.70 vs 0.95 ± 1.52, P