Cone-beam CT-based inter-fraction localization errors for tumors in the pelvic region |
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| Institution: | 1. Radiation Research Unit, European Institute of Oncology, Milano, Italy;2. Division of Radiation Oncology, European Institute of Oncology, Milano, Italy;3. Department of Oncology and Hemato-Oncology, University of Milan, Milano, Italy;4. Medical Physic Unit, European Institute of Oncology, Milano, Italy;5. Scientific Director, European Institute of Oncology, Milano, Italy;1. Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, Florida;2. Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California;1. Bismarck Cancer Center, Bismarck, ND;2. Department of Pathology, St. Alexius Hospital, Bismarck, ND;3. Department of Pathology, Altru Health System, Grand Forks, ND;4. Department of Pediatrics, University of Iowa Carver School of Medicine, Iowa City, IA;5. Department of Urology, Sanford Bismarck Medical Center, Bismarck, ND;6. Department of Radiation Oncology, University of Iowa Carver School of Medicine, Iowa City, IA;1. Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok 16424, Indonesia;2. Medical Imaging Research Center, Catholic University of Leuven, Leuven 3000, Belgium;1. Urology Institute, University Hospitals Case Medical Center, Cleveland, Ohio;2. Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio;3. Glickman Urologic and Kidney Institute, Cleveland Clinic, Cleveland, Ohio;1. Division of Radiotherapy, University Hospital Maggiore della Carità, Novara, Italy;2. Division of Radiation Oncology, Sichuan Cancer Center, Chengdu, China;3. Medical Physics, University Hospital Maggiore della Carità, Novara, Italy;4. Department of Translational Medicine, University of Piemonte Orientale, Novara, Italy;1. Graduate School of Medical Sciences, Kyushu University 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;2. Research Fellow at Japan Society for the Promotion of Science 5-3-1, Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan;3. Faculty of Medical Sciences, Kyushu University 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;4. Kyushu University Hospital 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan |
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| Abstract: | PurposeTo evaluate inter-fraction tumor localization errors (TE) in the RapidArc® treatment of pelvic cancers based on CBCT. Appropriate CTV-to PTV margins in a non-IGRT scenario have been proposed.MethodsData of 928 patients with prostate, gynecological, and rectum/anal canal cancers were retrospectively analyzed to determine systematic and random localization errors. Two protocols were used: daily online IGRT (d-IGRT) and weekly IGRT. The latter consisted in acquiring a CBCT for the first 3 fractions and subsequently once a week. TE for patients who underwent d-IGRT protocol were calculated using either all CBCTs or the first 3.ResultsThe systematic (and random) TE in the AP, LL, and SI direction were: for prostate bed 2.7(3.2), 2.3(2.8) and 1.9(2.2) mm; for prostate 4.2(3.1), 2.9(2.8) and 2.3(2.2) mm; for gynecological 3.0(3.6), 2.4(2.7) and 2.3(2.5) mm; for rectum 2.8(2.8), 2.4(2.8) and 2.3(2.5) mm; for anal canal 3.1(3.3), 2.1(2.5) and 2.2(2.7) mm. CTV-to-PTV margins determined from all CBCTs were 14 mm in the AP, 10 mm in the LL and 9–9.5 mm in the SI directions for the prostate and the gynecological groups and 9.5–10.5 mm in AP, 9 mm in LL and 8–10 mm in the SI direction for the prostate bed and the rectum/anal canal groups. If assessed on the basis of the first 3 CBCTs, the calculated CTV-to-PTV margins were slightly larger.Conclusionswithout IGRT, large CTV-to-PTV margins up to 15 mm are required to account for inter-fraction tumor localization errors. Daily IGRT should be used for all hypo-fractionated treatments to reduce margins and avoid increased toxicity to critical organs. |
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| Keywords: | Image-guided radiotherapy Cone-beam computed tomography Tumor localization errors Prostate cancer Gynecological cancer Rectum cancer |
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