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TECHNICAL NOTE
Year : 2018  |  Volume : 43  |  Issue : 2  |  Page : 129-135

Dosimetric, radiobiological and secondary cancer risk evaluation in head-and-neck three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, and volumetric modulated arc therapy: A phantom study


1 Department of Physics, Balochistan University of Information Technology, Engineering and Management Sciences, Quetta; Department of Physics, The Islamia University of Bahawalpur, Bahawalpur, Pakistan; The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
2 Department of Radiation Oncology, University of Toronto and Radiation Medicine Program, Princess Margaret Cancer Centre, Ontario, Toronto, Canada; Department of Physics, Hafiz Hayat Campus, University of Gujrat, Gujrat, Pakistan
3 Department of Physics, Balochistan University of Information Technology, Engineering and Management Sciences, Quetta, Pakistan
4 Department of Chemistry, Balochistan University of Information Technology, Engineering and Management Sciences, Quetta, Pakistan
5 Department of Radiation Oncology, University of Toronto and Radiation Medicine Program, Princess Margaret Cancer Centre, Ontario, Toronto, Canada
6 Department of Physics, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
7 The University of Texas MD Anderson Cancer Center, Houston, Texas, USA

Correspondence Address:
Dr. James C. L. Chow
Princess Margaret Cancer Centre, 700 University Avenue, Toronto, Ontario M5G 1Z5
Canada
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jmp.JMP_106_17

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This analysis estimated secondary cancer risks after volumetric modulated arc therapy (VMAT) and compared those risks to the risks associated with other modalities of head-and-neck (H&N) radiotherapy. Images of H&N anthropomorphic phantom were acquired with a computed tomography scanner and exported via digital imaging and communications in medicine (DICOM) standards to a treatment planning system. Treatment plans were performed using a VMAT dual-arc technique, a nine-field intensity-modulated radiation therapy (IMRT) technique, and a four-field three-dimensional conformal therapy (3DCRT) technique. The prescription dose was 66.0 Gy for all three techniques, but to accommodate the range of dosimeter responses, we delivered a single dose of 6.60 Gy to the isocenter. The lifetime risk for secondary cancers was estimated according to National Council on Radiation Protection and Measurements (NCRP) Report 116. VMAT delivered the lowest maximum doses to esophagus (23 Gy), and normal brain (40 Gy). In comparison, maximum doses for 3DCRT were 74% and 40%, higher than those for VMAT for the esophagus, and normal brain, respectively. The normal tissue complication probability and equivalent uniform dose for the brain (2.1%, 0.9%, 0.8% and 3.8 Gy, 2.6 Gy, 2.3 Gy) and esophagus (4.2%, 0.7%, 0.4% and 3.7 Gy, 2.2 Gy, 1.8 Gy) were calculated for the 3DCRT, IMRT and VMAT respectively. Fractional esophagus OAR volumes receiving more than 20 Gy were 3.6% for VMAT, 23.6% for IMRT, and 100% for 3DCRT. The calculations for mean doses, NTCP, EUD and OAR volumes suggest that the risk of secondary cancer induction after VMAT is lower than after IMRT and 3DCRT.


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