(P124) Dosimetric Comparison of Three-Dimensional Conformal Proton Radiotherapy and Intensity-Modulated Proton Therapy for Treatment of Pediatric Hodgkin Lymphoma

Jamie M. Pinckard, BS, William W. Chance, MD, Cody N. Crawford, CMD, Shengpeng Jiang, Xiaodong Zhang, PhD, Anita Mahajan, MD; UT Health Science Center, San Antonio; UT MD Anderson Cancer Center

OBJECTIVES: Thoracic irradiation in pediatric patients is associated with serious long-term adverse effects. We compared the target coverage and dose distribution in normal tissues in pediatric patients with Hodgkin lymphoma using three-dimensional conformal proton radiotherapy (3DPRT) and intensity-modulated proton therapy (IMPT).

METHODS: From 2009–2014, seven pediatric patients with Hodgkin lymphoma with intrathoracic involvement received proton therapy to 21–25.2 Cobalt Gray Equivalents (CGE) in 15 fractions. Five patients received 3DPRT, and two patients received IMPT. To compare dosimetric endpoints between the modalities, an additional 3DPRT or IMPT plan was generated for each patient (n = 14 plans). Mean doses to target and nontarget tissues were then compared between 3DPRT and IMPT using the Wilcoxon matched-pair signed-rank test.

RESULTS: The planning target volume was adequately treated using both techniques. When compared to 3DPRT, IMPT resulted in a lower mean total lung dose (632 cGy vs 737 cGy; P < .05) and mean heart dose (797 cGy vs 972 cGy; P < .05). The mean dose to the breasts, thyroid gland, esophagus, pancreas, stomach, and liver were similar between the modalities.

CONCLUSIONS: In pediatric patients with intrathoracic involvement, IMPT produced significantly lower doses to the lung and heart compared with 3DPRT. Additional studies will be needed to determine the clinical benefit of these findings.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org