Dosimetric Comparison of Three Different Involved Nodal Irradiation Techniques for Stage II Hodgkin's Lymphoma Patients: Conventional Radiotherapy, Intensity-Modulated Radiotherapy, and Three-Dimensional Proton Radiotherapy

Purpose To compare the dose distribution to targeted and nontargeted tissues in Hodgkin's lymphoma patients using conventional radiotherapy (CRT), intensity-modulated RT (IMRT), and three-dimensional proton RT (3D-PRT). Methods and Materials CRT, IMRT, and 3D-PRT treatment plans delivering 30 cobalt Gray equivalent (CGE)/Gy to an involved nodal field were created for 9 Stage II Hodgkin's lymphoma patients ( n = 27 plans). The dosimetric endpoints were compared. Results The planning target volume was adequately treated using all three techniques. The IMRT plan produced the most conformal high-dose distribution; however, the 3D-PRT plan delivered the lowest mean dose to nontarget tissues, including the breast, lung, and total body. The relative reduction in the absolute lung volume receiving doses of 4–16 CGE/Gy for 3D-PRT compared with CRT ranged from 26% to 37% ( p < .05), and the relative reduction in the absolute lung volume receiving doses of 4–10 CGE/Gy for 3D-PRT compared with IMRT was 48–65% ( p < .05). The relative reduction in absolute total body volume receiving 4–30 CGE/Gy for 3D-PRT compared with CRT was 47% ( p < .05). The relative reduction in absolute total body volume receiving a dose of 4 CGE/Gy for 3D-PRT compared with IMRT was 63% ( p = .03). The mean dose to the breast was significantly less for 3D-PRT than for either IMRT or CRT ( p = .03) The mean dose and absolute volume receiving 4–30 CGE/Gy for the heart, thyroid, and salivary glands were similar for the three modalities. Conclusion In this favorable subset of Hodgkin's lymphoma patients without disease in or below the hila, 3D-PRT significantly reduced the dose to the breast, lung, and total body. These observed dosimetric advantages might improve the clinical outcomes of Hodgkin's lymphoma patients by reducing the risk of late radiation effects related to low-to-moderate doses in nontargeted tissues.