Kyenzeh TL1, Lenards N2, Gutierrez AN3 and Zheng Shi1*
1Department of Radiation Oncology, Mays Cancer Center, UT Health San Antonio MD Anderson Cancer Center, USA 2Department of Health Professions, College of Science and Health, University of Wisconsin–La Crosse, USA 3Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, USAFulltext PDF
Purpose: The aim of this study was to evaluate the dosimetric differences between Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) in regard to target dose conformity, normal tissue and critical structure sparing for Simultaneous Integrated Boost (SIB) treatment plans. Methods: Ten (n=10) previously treated patients were randomly selected from a pool of patients with high-risk adenocarcinoma of the prostate after laparoscopic radical prostatectomy. The target volumes were defined per RTOG 0534 protocol. The VMAT plans consisted of dual arcs using 6 MV. Nine evenly spaced co-planar beams were used for the IMRT plans. A total of 20 plans were generated; 10 in each technique. The pelvic nodes were treated to 45 Gy in 1.8 Gy daily fractions. The prostatic fossa was simultaneously treated to 62.5 Gy delivered in 2.5 Gy daily fractions. The goal was to deliver the prescription dose to cover 95% of the high dose Planning Target Volume (PTV 62.5). Parameters evaluated included the Conformity Index (CI) at the 100% isodose line, total Monitor Units (MU), critical organ dose, and Normal Tissue Integral Dose (NTID). Results: Target volume conformity was shown to increase by 4.0% (p<0.01) for VMAT over IMRT when delivering SIB adjuvant radiation therapy for postoperative cancer patients. Additionally, normal tissue integral dose data suggest that the dose delivered to non-tumor tissue was lower for VMAT for the 30% (p<0.01), 40% (p<0.01), and 50% (p<0.04) isodose volumes. Conclusion: For equivalent coverage, VMAT technique provided reduced normal tissue dose and better target conformity. Furthermore, VMAT reduced the MU usage resulting in shorter treatment delivery time.
Prostatic fossa; Normal Tissue Integral Dose (NTID); Simultaneous Integrated Boost (SIB); Prostate cancer
Kyenzeh TL, Lenards N, Gutierrez AN, Zheng Shi. Simultaneous Integrated Boost Plan Comparison between Static Intensity-Modulated Radiotherapy and Volumetric-Modulated Arc Therapy for Prostate Fossa and Lymph Node Irradiation. Clin Oncol. 2019;4:1667.