Clinical Investigation: Lymphoma Effective Dose Reduction to Cardiac Structures Using Protons Compared With 3DCRT and IMRT in Mediastinal Hodgkin Lymphoma Bradford S. Hoppe, M.D., M.P.H.,* Stella Flampouri, Ph.D.,* Zhong Su, Ph.D.,* Naeem Latif, M.D., y Nam H. Dang, M.D., Ph.D., x James Lynch, M.D., x Michael Joyce, M.D., z Eric Sandler, M.D., z Zuofeng Li, Ph.D.,* and Nancy P. Mendenhall, M.D.* From the Departments of *Radiation Oncology and y Medical Oncology, University of Florida Proton Therapy Institute; the z Division of Hematology/Oncology, Nemours Children’s Clinic and Wolfson Children’s Hospital, Jacksonville; and the x Department of Medical Oncology, University of Florida Shands Cancer Center, Gainesville, FL Received Oct 23, 2011, and in revised form Oct 25, 2011. Accepted for publication Dec 8, 2011 Summary We investigated the dosi- metric impact of proton therapy on various cardiac subunits in patients with Hodgkin lymphoma. Compared with three- dimensional conformal radiotherapy and intensity- modulated radiation therapy, proton therapy reduced the radiation doses to all major cardiac subunits. Limiting the doses to these structures should translate into lower rates of cardiac toxicities. Purpose: We investigated the dosimetric impact of proton therapy (PT) on various cardiac subunits in patients with Hodgkin lymphoma (HL). Methods and Materials: From June 2009 through December 2010, 13 patients were enrolled on an institutional review board-approved protocol for consolidative involved-node radiotherapy (INRT) for HL. Three separate treatment plans were developed prospectively by using three- dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and PT. Cardiac subunits were retrospectively contoured on the 11 patients with intravenous- contrast simulation scans, and the doses were calculated for all treatment plans. A Wilcoxon paired test was performed to evaluate the statistical significance (p < 0.05) of 3DCRT and IMRT compared with PT. Results: The mean heart doses were 21 Gy, 12 Gy, and 8 Gy (relative biologic effectiveness [RBE]) with 3DCRT, IMRT, and PT, respectively. Compared with 3DCRT and IMRT, PT reduced the mean doses to the left and right atria; the left and right ventricles; the aortic, mitral, and tricuspid valves; and the left anterior descending, left circumflex, and right circumflex coro- nary arteries. Conclusions: Compared with 3DCRT and IMRT, PT reduced the radiation doses to all major cardiac subunits. Limiting the doses to these structures should translate into lower rates of cardiac toxicities. Ó 2012 Elsevier Inc. Keywords: Hodgkin lymphoma, Proton therapy, Radiation therapy, Cardiac dose, Dosimetry Reprint requests to: Bradford S. Hoppe, M.D., University of Florida Proton Therapy Institute, 2015 North Jefferson St., Jacksonville, FL 32206. Tel: (904) 588-1800; Fax: (904) 588-1300; E-mail: bhoppe@floridaproton. org Conflict of interest: none. Int J Radiation Oncol Biol Phys, Vol. 84, No. 2, pp. 449e455, 2012 0360-3016/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.ijrobp.2011.12.034 Radiation Oncology International Journal of biology physics www.redjournal.org