Dosimetric Comparison Of Radiation Treatment Planning Techniques By Multiple International Institutions For A Benchmark Head And Neck Case

To report on dosimetric characteristics of “standard”, 3D conformal, and IMRT treatment plans from different planning systems and multiple international institutions for a benchmark head and neck cancer case. Prior to participation in a head and neck cancer multi-center phase 3 clinical trial, prospective institutions had to satisfactorily complete a representative (benchmark) case that was provided as a CT study in DICOM format by the Quality Assurance Review Center. 57 CT-based treatment plans for a T2N1 larynx patient were satisfactorily completed according to the protocol guidelines by institutions in 18 countries on 5 continents using 13 different planning systems. Planning options included “standard” (conventional beam orientations, e.g., parallel opposed, designed to the reconstructed CT anatomy), 3D conformal, or IMRT techniques. 18 “standard” plans, 16 3D conformal plans, and 24 IMRT plans were approved. Plans were characterized by analyses of the dose volume histograms for minimum dose to the macroscopic disease (GTV prescribed to 70 Gy), the dose received by 90% and 10% volume of the gross disease plus 0.5cm (prescribed to 70 Gy), the dose received by 90% volume of macroscopic plus microscopic disease plus 0.5 cm (PTV190) (prescribed to 44-50 Gy), and maximum dose to the spinal cord. IMRT, 3D conformal, and “standard” planning techniques were able to satisfy the dosimetric guidelines of the protocol. More plan revisions were required for the “standard” and 3D techniques than for the IMRT plans. 3 sites whose initial IMRT plans were unsatisfactory submitted "standard" plans that were approved. 9 sites were excluded because of inability to generate a satisfactory plan. Overall, the IMRT plans had a greater minimum dose to the target volumes. GTV minimum dose in 19/24 IMRT plans was >69.0 Gy; it was < 68.0 Gy for 9/18 “standard” and 9/16 3D conformal plans. PTV190 was at least 50.0 Gy for 21 IMRT plans but for only 4 “standard” and 4 3D conformal plans. Maximum dose to the spinal cord was <46.0 Gy for all but 3 IMRT plans; but greater than 46.0 G for 9 “standard” plans and 13 3D plans. Dose heterogeneity to target volumes was slightly less with the IMRT plans. No characteristic was identified to distinguish the 3D conformal plans from the “standard” planning plans. Institutions in diverse geographic locations were able to load and plan on a DICOM CT scan using diverse treatment planning systems. Approximately the same number chose to use “standard”, 3D conformal, and IMRT planning. All techniques were able to achieve satisfactory dose distributions. IMRT plans did have better dose coverage with less heterogeneity to target volumes and lower spinal cord doses than either the 3D conformal or the “standard” plans.