Clinical delivery of intensity modulated conformal radiotherapy for relapsed or second-primary head and neck cancer using a multileaf collimator with dynamic control |
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Authors: | Wilfried De Neve, Wezner De Gersem, Sylvie Derycke, Gert De Meerleer, Mieke Moerman, Marie-Th l se Bate, Bart Van Duyse, Luc Vakaet, Yves De Deene, Bart Mersseman,Carlos De Waeter |
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Affiliation: | a Division of Radiotherapy, University Hospital Gent (U.Z.G.), Gent, Belgium b Department of Head and Neck Surgery, University Hospital Gent (U.Z.G.), Gent, Belgium |
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Abstract: | Background and purpose: Concave dose distributions generated by intensity modulated radiotherapy (IMRT) were applied to re-irradiate three patients with pharyngeal cancer. Patients, materials and methods: Conventional radiotherapy for oropharyngeal (patients 1 and 3) or nasopharyngeal (patient 2) cancers was followed by relapsing or new tumors in the nasopharynx (patients 1 and 2) and hypopharynx (patient 3). Six non-opposed coplanar intensity modulated beams were generated by combining non-modulated beamparts with intensities (weights) obtained by minimizing a biophysical objective function. Beamparts were delivered by a dynamic MLC (Elekta Oncology Systems, Crawley, UK) forced in step and shoot mode. Results and conclusions: Median PTV-doses (and ranges) for the three patients were 73 (65–78), 67 (59–72) and 63 (48–68) Gy. Maximum point doses to brain stem and spinal cord were, respectively, 67 Gy (60% of volume below 30 Gy) and 32 Gy (97% below 10 Gy) for patient 1; 60 Gy (69% below 30 Gy) and 34 Gy (92% below 10 Gy) for patient 2 and 21 Gy (96% below 10 Gy) at spinal cord for patient 3. Maximum point doses to the mandible were 69 Gy for patient 1 and 64 Gy for patient 2 with, respectively, 66 and 92% of the volume below 20 Gy. A treatment session, using the dynamic MLC, was finished within a 15-min time slot. |
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Keywords: | cancer radiotherapy nasopharynx cancer oropharynx cancer |
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