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| Various Techniques of Bone Marrow-Sparing Intensity Modulated Radiation Therapy in Cervical Cancer Treated with Definitive Radiotherapy |
| Cancer Hospital of Shantou University Medical College， Shantou 515031， China |
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Abstract Objective： To compare static intensity-modulated radiation therapy（ IMRT） technique with various arcs of volumetric-modulated arc radiation therapy（ VMAT） techniques in patients with cervical cancer treated with definitive bone morrow-sparing whole pelvic radiotherapy， and to explore a better treatment management. Method：9 CT image sets of staged ⅡA-ⅢB cervical cancer patients， treated in Cancer Hospital of Shantou University Medical College， were included. Nine fixed-field IMRT（ FF-IMRT） plans and two arcs， three arcs， four arcs VMAT plans（ 2AVMAT，3A-VMAT， 4A-VMAT） were created and compared for each patient. Plans were evaluated on parameters of tumor target volume， pelvic bone marrow（ PBM）， other pelvic organs， plan MUs and delivery time. Result： Four groups of 2A-VMAT， 3A-VMAT， 4A-VMAT and IMRT plans provide equivalent tumor target volume coverage， conformity，
homogeneity and sparing of PBM respected to V10，V20，V40. Three VMAT plans demonstrate the similar organs sparing. VMAT was slightly superior to FF-IMRT with the sparing of bowel. However， FF-IMRT showed better rectum sparing than that of 3A-VMAT. The monitor units of IMRT， 2A-VMAT， 3A-VMAT and 4A-VMAT were（ 1850.3±227.8）MU， （848.4±58.8）MU，（ 835.0±76.2）MU and（ 910.8±43.3）MU， respectively， while delivery time were（ 353.2±25.1）
s，（ 136.2±3.6）s，（ 211.2±3.5）s and（ 286.2±3.4）s， respectively. There were significant differences of monitor units （MUs） and treatment time among four plans. IMRT plan had more MUs and treatment time than that of VMAT plans， and two arcs VMAT plan had the least MUs and treatment time. Conclusion： Considering the physical factors and biological effects during the cervical cancer definitive radiotherapy with pelvic bone marrow-sparing， 2 arcs VMAT plan would be the best choice for the treatment planning.
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