title: A comparison of mantle versus involved-field radiotherapy for Hodgkin's lymphoma: reduction in normal tissue dose and second cancer risk.
abstract: BACKGROUND
  Hodgkin's lymphoma (HL) survivors who undergo radiotherapy experience increased risks of second cancers (SC) and cardiac sequelae. To reduce such risks, extended-field radiotherapy (RT) for HL has largely been replaced by involved field radiotherapy (IFRT). While it has generally been assumed that IFRT will reduce SC risks, there are few data that quantify the reduction in dose to normal tissues associated with modern RT practice for patients with mediastinal HL, and no estimates of the expected reduction in SC risk.
  
  
  METHODS
  Organ-specific dose-volume histograms (DVH) were generated for 41 patients receiving 35 Gy mantle RT, 35 Gy IFRT, or 20 Gy IFRT, and integrated organ mean doses were compared for the three protocols. Organ-specific SC risk estimates were estimated using a dosimetric risk-modeling approach, analyzing DVH data with quantitative, mechanistic models of radiation-induced cancer.
  
  
  RESULTS
  Dose reductions resulted in corresponding reductions in predicted excess relative risks (ERR) for SC induction. Moving from 35 Gy mantle RT to 35 Gy IFRT reduces predicted ERR for female breast and lung cancer by approximately 65%, and for male lung cancer by approximately 35%; moving from 35 Gy IFRT to 20 Gy IFRT reduces predicted ERRs approximately 40% more. The median reduction in integral dose to the whole heart with the transition to 35 Gy IFRT was 35%, with a smaller (2%) reduction in dose to proximal coronary arteries. There was no significant reduction in thyroid dose.
  
  
  CONCLUSIONS
  The significant decreases estimated for radiation-induced SC risks associated with modern IFRT provide strong support for the use of IFRT to reduce the late effects of treatment. The approach employed here can provide new insight into the risks associated with contemporary IFRT for HL, and may facilitate the counseling of patients regarding the risks associated with this treatment.
authors.affiliation: University of Toronto, Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada. engsiew.koh@rmp.uhn.on.ca
authors.forename: Eng-Siew
authors.initials: ES
authors.lastname: Koh
authors.forename: Tu Huan
authors.initials: TH
authors.lastname: Tran
authors.forename: Mostafa
authors.initials: M
authors.lastname: Heydarian
authors.forename: Rainer K
authors.initials: RK
authors.lastname: Sachs
authors.forename: Richard W
authors.initials: RW
authors.lastname: Tsang
authors.forename: David J
authors.initials: DJ
authors.lastname: Brenner
authors.forename: Melania
authors.initials: M
authors.lastname: Pintilie
authors.forename: Tony
authors.initials: T
authors.lastname: Xu
authors.forename: June
authors.initials: J
authors.lastname: Chung
authors.forename: Narinder
authors.initials: N
authors.lastname: Paul
authors.forename: David C
authors.initials: DC
authors.lastname: Hodgson
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006689:Hodgkin Disease / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy; D008297:Male; D008482:Mediastinum / Q000473:pathology; D008495:Medical Oncology / Q000379:methods; D008875:Middle Aged; D009362:Neoplasm Metastasis; D016609:Neoplasms, Second Primary / Q000517:prevention & control / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods; D011878:Radiotherapy / Q000379:methods*; D012306:Risk; D016896:Treatment Outcome