Volumetric-modulated arc radiotherapy for pancreatic malignancies: Dosimetric comparison with sliding-window intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy |
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| Affiliation: | 2. Department of Radiation Oncology, Acibadem University, Istanbul, Turkey;3. Institute of Biomedical Engineering, Bogazici University Istanbul, Turkey;4. Istanbul University, Institute of Oncology, Istanbul, Turkey;2. Department of Radiation Oncology, Northwestern University Feinberg School of Medicine, Northwestern University, Northwestern Memorial Hospital, Chicago, IL;2. Optimization and Systems Theory, KTH Royal Institute of Technology, Stockholm, Sweden;3. RaySearch Laboratories, Stockholm, Sweden;4. Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast, Northern Ireland, UK;2. Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan;3. Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan;1. Medical Physics Unit, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy;2. Department of Oncology, Radiation Oncology, University of Turin, Via Genova 3, 10126 Turin, Italy;3. Radiotherapy Unit, A.O.U. Città della Salute e della Scienza, Corso Bramante 88/90, 10126 Turin, Italy |
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| Abstract: | Volumetric-modulated arc radiotherapy (VMAT) is an iteration of intensity-modulated radiotherapy (IMRT), both of which deliver highly conformal dose distributions. Studies have shown the superiority of VMAT and IMRT in comparison with 3-dimensional conformal radiotherapy (3D-CRT) in planning target volume (PTV) coverage and organs-at-risk (OARs) sparing. This is the first study examining the benefits of VMAT in pancreatic cancer for doses more than 55.8 Gy. A planning study comparing 3D-CRT, IMRT, and VMAT was performed in 20 patients with pancreatic cancer. Treatments were planned for a 25-fraction delivery of 45 Gy to a large field followed by a reduced-volume 8-fraction external beam boost to 59.4 Gy in total. OARs and PTV doses, conformality index (CI) deviations from 1.0, monitor units (MUs) delivered, and isodose volumes were compared. IMRT and VMAT CI deviations from 1.0 for the large-field and the boost plans were equivalent (large field: 0.032 and 0.046, respectively; boost: 0.042 and 0.037, respectively; p > 0.05 for all comparisons). Both IMRT and VMAT CI deviations from 1.0 were statistically superior to 3D-CRT (large field: 0.217, boost: 0.177; p < 0.05 for all comparisons). VMAT showed reduction of the mean dose to the boost PTV (VMAT: 61.4 Gy, IMRT: 62.4 Gy, and 3D-CRT: 62.3 Gy; p < 0.05). The mean number of MUs per fraction was significantly lower for VMAT for both the large-field and the boost plans. VMAT delivery time was less than 3 minutes compared with 8 minutes for IMRT. Although no statistically significant dose reduction to the OARs was identified when comparing VMAT with IMRT, VMAT showed a reduction in the volumes of the 100% isodose line for the large-field plans. Dose escalation to 59.4 Gy in pancreatic cancer is dosimetrically feasible with shorter treatment times, fewer MUs delivered, and comparable CIs for VMAT when compared with IMRT. |
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| Keywords: | Pancreas VMAT IMRT 3D-CRT |
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