Clinical studies on the simultaneous integrated boost method using intensity modulated radiotherapy (IMRT)

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We have finished a pilot study on the treatment of malignant gliomas with intensity modulated radiotherapy (IMRT) using a simultaneous integrated boost (SIB) method. Our IMRT regimen delivered 70 Gy/28 fractions (fr)/daily 2.5 Gy to the gross tumor volume (GTV) with a 0.5-cm margin defined as the planning target volume annulus (PTV-G) and 56 Gy/28 fr/daily 2.0 Gy to the surrounding edema defined as the planning target volume annulus (PTV-a). Unfortunately, all the 13 patients experienced tumor recurrence. The 1-year and 2-year overall survival rate for all the patients was 77 and 31%, respectively. In conclusion, our IMRT regimen did not prevent tumor progression. However, the ability of IMRT to deliver highly conformative doses to two contiguous targets, GTV and the surrounding edema, justifies its application to malignant gliomas.Clinical results of 74 patients with pharyngeal cancer treated with IMRT. The 5-year survival rate for the 27 patients with nasopharyngeal cancer was as goo … More d as 75%. The 3-year survival rates for oropharyngeal and hypopharyngeal cancers were 87% and 48%, respectively. Only 1/4 of the patients treated by IMRT complained moderate xerostomia (grade 2) one year after treatment. For early oropharyngeal cancer with T1,2NOMO disease, treatment planning Of SIB method was established, and applied for three patients. Our IMRT regimen delivered 66 Gy/30 fr/daily 2.2 Gy to the GTV with a 0.5-cm margin and 54 Gy/30 fr /daily 1.8 Gy to the prophylactic lymph node areas.Positron emission tomography (PET) is useful for radiation therapy treatment planning. However, the size of PET delineation changes significantly dependent on its threshold value, and the PET image affects the target delineation clinically. To determine an appropriate threshold value for delineation of the target in PET images, static and moving phantom studies were performed. When a threshold value of 35% of the maximum 18FDG activity was adopted, PET-images were almost the same for static and moving phantom spheres of 22〜37mm in the axial plane. In moving phantom experiments with a periodic motion of 4 seconds, the maximum 18FDG activity of spheres dropped significantly dependent on moving distance. In addition, PET images have the potential to provide an individualized internal target volume (ITV). Less