title: Pencil beam scanning proton therapy for treatment of the retroperitoneum after nephrectomy for Wilms tumor: A dosimetric comparison study.
abstract: Multimodality treatment for patients with Wilms tumor has improved patient survival, but is associated with acute and long-term toxicity, partially due to irradiation. Proton therapy using pencil beam scanning (PBS) is a promising technique to reduce dose to organs at risk (OAR). In this study, we evaluate PBS plans for postoperative irradiation in patients with Wilms tumor.
  
  
  
  Patients were treated with anterior-posterior-posterior-anterior (AP-PA) photon fields encompassing the preoperative tumor volume. Patients requiring whole lung irradiation were treated with AP-PA photon fields covering the bilateral lungs. Prescription doses were generally 1,080 and 1,200 cGy, respectively. Flank PBS plans encompassing the ipsilateral retroperitoneum and para-arotic nodes were generated for dosimetric evaluation.
  
  
  
  Treatment records and comparison plans of 11 patients were reviewed. Mean dose and median dose to 50% or more of the contralateral kidney (D50) were 135 cGy and 139 cGy with photons and 52 cGy relative biological effectiveness (RBE) (P = 0.009) and 5 cGy RBE (P = 0.000001) with PBS. Mean dose and median D50 to bowel was 639 cGy and 979 cGy with photons and 379 cGy RBE (P = 0.001) and 47 cGy RBE (P = 0.004) with PBS. Mean dose and median D50 to the liver were 755 cGy and 1,013 cGy with photons and 411 cGy RBE (P = 0.02) and 132 cGy RBE (P = 0.02) with PBS. For patients with right-sided tumors, mean liver dose following sequential whole lung irradiation was 1,252 cGy with photons and 845 cGy RBE (P = 0.04) with PBS.
  
  
  
  PBS proton therapy is a feasible method for irradiating the retroperitoneum and provides significant sparing of dose to critical OAR. This may translate to improved long-term health outcomes for patients and warrants further clinical investigation.
authors: Department of Radiation Oncology, Perelman Center for Advanced Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors: Jennifer
authors: J
authors: Vogel
authors: Department of Radiation Oncology, Perelman Center for Advanced Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors: Haibo
authors: H
authors: Lin
authors: Medical Physics Department, Memorial Sloan-Kettering Cancer Center, 1275 First Avenue, New York, NY 10065.
authors: Stefan
authors: S
authors: Both
authors: Department of Radiation Oncology, Perelman Center for Advanced Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors: Zelig
authors: Z
authors: Tochner
authors: Department of Oncology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors: Frank
authors: F
authors: Balis
authors: Department of Radiation Oncology, Perelman Center for Advanced Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors: Christine
authors: C
authors: Hill-Kayser
mesh_terms: D002648:Child; D002675:Child, Preschool; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007680:Kidney Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*; D008297:Male; D009367:Neoplasm Staging; D009392:Nephrectomy / Q000009:adverse effects*; D058958:Organs at Risk / Q000528:radiation effects; D011379:Prognosis; D061766:Proton Therapy; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012186:Retroperitoneal Neoplasms / Q000209:etiology / Q000532:radiotherapy* / Q000556:secondary; D009396:Wilms Tumor / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery*
keywords: Wilms tumor; proton; radiation therapy