Conformal proton radiation treatment for retroperitoneal neuroblastoma: Introduction of a novel technique

Background Postoperative irradiation for locoregionally advanced neuroblast oma requires coverage of the paraspinal recroperitoneum. The proximity of b oth kidneys and the liver, and if more complex target configuration, can po se a dosimetric challenge for conventional X-ray treatment and intraoperati ve irradiation. We utilized proton radiation therapy (PRT) to reduce dose t o uninvolved kidneys, liver, intestine; and spinal cord. Procedure. A 4-yea r-old male underwent PRT for neuroblastoma of the right adrenal gland, foll owing chemotherapy and delayed surgical resection. Clinical target volume ( CTV), boost volume, and normal structures were outlined on the 3D treatment planning CT scan. The patient received 25.2 CGE (cobalt Gray equivalent) t o the CTV and 34.2 CGE to the boost region, using 1.8 CGE per fraction, fiv e treatments per week. Dose-volume histograms (DVHs) were obtained for targ et and nontarget structures. Results, The 95% isodose volume enclosed CN an d boost volumes. The dose to 50% of the ipsilateral kidney, with tumor invo lvement of the medial renal surface, was less than or equal to 16 CGE (47% of prescribed total dose). Doses to 50% and 20% of the contralateral kidney in close proximity to deep left-side, paraspinal soft tissue involvement w ere restricted to 1 CGE and 10 CGE, respectively. Eighty percent of the liv er received < 27 CGE (80% of prescribed dose). Using a patch technique, uni que to charged particle therapy, the spinal cord was almost completely spar ed during boost volume irradiation. Conclusions. PRT can achieve excellent dose conformity for advanced retroperitoneal, paraspinal lesions, while res pecting normal tissue tolerance levels. (C) 2001 Wiley-Liss, inc.