PV QA 3 - Poster Viewing Q&A 3
TU_7_3179 - A Prospective Study Developing Decision Algorithm for Respiration Controlled Radiation Therapy
Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3
A Prospective Study Developing Decision Algorithm for Respiration Controlled Radiation Therapy
E. Kim1, E. K. Chie1, H. C. Kang2, S. Y. Park2, C. H. Choi2, J. M. Park2, J. I. Kim2, and H. G. Wu2; 1Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea, Republic of (South), 2Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of (South)
Purpose/Objective(s): The primary goal was to develop patient selection decision algorithm based on pre-treatment clinical factors for patients undergoing radiotherapy to intraabdominal target. A prospective study was carried out to compare the plan quality of volumetric modulated arc therapy (VMAT) with a linear accelerator (LINAC) to that of respiration-gated intensity modulated radiation therapy (IMRT) with magnetic-resonance (MR) image-guided tri-60Co system.
Materials/Methods: This study was designed to test the null hypothesis that dose-volume parameter of LINAC and that of tri-60Co system plans are the same. The study was designed to test given hypothesis with alpha 0.01 and beta 0.1 using paired T-test. Target accrual was adjusted to incorporate the 20% dropout rate. LINAC plans were generated from 4D CT simulation images with abdominal compression and forced shallow breathing, whereas tri-60Co system plans were generated from breath hold fused CT simulation and MR simulation images. Competing plans from each set-up were generated and dose-volumetric parameters from both plans were obtained for analysis.
Results: A total of 102 patients were enrolled, and 27 patients were excluded due to the innate imbalance in a treatment plan. There were 32 patients with liver tumor (Group A), 21 patients with pancreas or extrahepatic bile duct cancer (Group B), and 22 patients with metastatic abdominal lymph node or adrenal gland tumor (Group C). There were 20 with LINAC plans and 12 with tri-60Co plans in Group A, 13 with LINAC plans and 8 with tri-60Co plans in Group B, and 14 with LINAC plans and 8 with tri-60Co plans in Group C. The average planning target volumes were significantly higher with LINAC vs. tri-60Co plans in all groups (p < 0.001, < 0.001, and 0.001, respectively). In addition, mean doses to liver were increased with tri-60Co vs. LINAC (p = 0.004, < 0.001, and < 0.001, respectively). In Group A, D1cc of stomach and duodenum were higher in tri-60Co vs. LINAC, respectively (p = 0.004 and 0.045, respectively). In Group B and C, however, D1cc of stomach and duodenum were not significantly different between two plans. But, mean doses and D1cc of kidney were significantly higher in tri-60Co plan (mean dose, p = 0.049 and 0.003; D1cc, p = 0.003 and 0.01, respectively). Tri-60Co system was selected for patients whose GTV abutted hollow organ in overall patients. In Group B and C, patients with the tumor in contact with hollow organ and small respiratory motion (diaphragm movement < 7mm) showed a trend towards likely to be treated with tri-60Co system plan.
Conclusion: The quality of VMAT plans was superior to that of tri-60Co plans for the majority of patients undergoing radiotherapy for an abdominal target. However, respiratory gated image-guided radiotherapy with tri-60Co system offered benefits to patients with organs at risk abutted to target. Furthermore, in minority of patients, only MR guided respiration-gated radiotherapy met planning parameters and was thus clinically applicable.
Author Disclosure: E. Kim: None. E. Chie: None. H. Wu: None.