title: Adjuvant radiation therapy for early stage seminoma: proton versus photon planning comparison and modeling of second cancer risk.
abstract: OBJECTIVE
  Given concerns of excess malignancies following adjuvant radiation for seminoma, we evaluated photon and proton beam therapy (PBT) treatment plans to assess dose distributions to organs at risk and model rates of second cancers.
  
  
  METHODS
  Ten stage I seminoma patients who were treated with conventional para-aortic AP-PA photon radiation to 25.5 Gy at Massachusetts General Hospital had PBT plans generated (AP-PA, PA alone). Dose differences to critical organs were examined. Risks of second primary malignancies were calculated.
  
  
  RESULTS
  PBT plans were superior to photons in limiting dose to organs at risk. PBT decreased dose by 46% (8.2 Gy) and 64% (10.2 Gy) to the stomach and large bowel, respectively (p<0.01). Notably, PBT was found to avert 300 excess second cancers among 10,000 men treated at a median age of 39 and surviving to 75 (p<0.01).
  
  
  CONCLUSIONS
  In this study, the use of protons provided a favorable dose distribution with an ability to limit unnecessary exposure to critical normal structures in the treatment of early-stage seminoma. It is expected that this will translate into decreased acute toxicity and reduced risk of second cancers, for which prospective studies are warranted.
authors.affiliation: Massachusetts General Hospital, Department of Radiation Oncology, Boston, MA 02114, USA. jefstathiou@partners.org
authors.forename: Jason A
authors.initials: JA
authors.lastname: Efstathiou
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Paly
authors.forename: Hsiao-Ming
authors.initials: HM
authors.lastname: Lu
authors.forename: Basit S
authors.initials: BS
authors.lastname: Athar
authors.forename: Maryam
authors.initials: M
authors.lastname: Moteabbed
authors.forename: Andrzej
authors.initials: A
authors.lastname: Niemierko
authors.forename: Judith A
authors.initials: JA
authors.lastname: Adams
authors.forename: Justin E
authors.initials: JE
authors.lastname: Bekelman
authors.forename: William U
authors.initials: WU
authors.lastname: Shipley
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Zietman
authors.forename: Harald
authors.initials: H
authors.lastname: Paganetti
mesh_terms: D000328:Adult; D006801:Humans; D008297:Male; D009367:Neoplasm Staging; D009381:Neoplasms, Radiation-Induced; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use*; D061766:Proton Therapy; D011522:Protons / Q000009:adverse effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D012307:Risk Factors; D018239:Seminoma / Q000473:pathology / Q000532:radiotherapy*; D013736:Testicular Neoplasms / Q000532:radiotherapy*
chemical_list: D011522:Protons