title: Different IMRT solutions vs. 3D-conformal radiotherapy in early stage Hodgkin's Lymphoma: dosimetric comparison and clinical considerations.
abstract: BACKGROUND
  Radiotherapy in Hodgkin's Lymphoma (HL) is currently evolving with new attempts to further reduce radiation volumes to the involved-node concept (Involved Nodes Radiation Therapy, INRT) and with the use of intensity modulated radiotherapy (IMRT). Currently, IMRT can be planned and delivered with several techniques, and its role is not completely clear. We designed a planning study on a typical dataset drawn from clinical routine with the aim of comparing different IMRT solutions in terms of plan quality and treatment delivery efficiency.
  
  
  METHODS
  A total of 10 young female patients affected with early stage mediastinal HL and treated with 30 Gy INRT after ABVD-based chemotherapy were selected from our database. Five different treatment techniques were compared: 3D-CRT, VMAT (single arc), B-VMAT ("butterfly", multiple arcs), Helical Tomotherapy (HT) and Tomodirect (TD). Beam energy was 6 MV, and all IMRT planning solutions were optimized by inverse planning with specific dose-volume constraints on OAR (breasts, lungs, thyroid gland, coronary ostia, heart). Dose-Volume Histograms (DVHs) and Conformity Number (CN) were calculated and then compared, both for target and OAR by a statistical analysis (Wilcoxon's Test).
  
  
  RESULTS
  PTV coverage was reached for all plans (V95% ≥ 95%); highest mean CN were obtained with HT (0.77) and VMAT (0.76). B-VMAT showed intermediate CN mean values (0.67), while the lowest CN were obtained with TD (0.30) and 3D-CRT techniques (0.30). A trend of inverse correlation between higher CN and larger healthy tissues volumes receiving low radiation doses was shown for lungs and breasts. For thyroid gland and heart/coronary ostia, HT, VMAT and B-VMAT techniques allowed a better sparing in terms of both Dmean and volumes receiving intermediate-high doses compared to 3D-CRT and TD.
  
  
  CONCLUSIONS
  IMRT techniques showed superior target coverage and OAR sparing, with, as an expected consequence, larger volumes of healthy tissues (lungs, breasts) receiving low doses. Among the different IMRT techniques, HT and VMAT showed higher levels of conformation; B-VMAT and HT emerged as the planning solutions able to achieve the most balanced compromise between higher conformation around the target and smaller volumes of OAR exposed to lower doses (typical of 3D-CRT).
authors.affiliation: University of Turin, Department of Oncology, Radiation Oncology Unit, Turin, Italy. christian.fiandra@unito.it
authors.forename: Christian
authors.initials: C
authors.lastname: Fiandra
authors.forename: Andrea Riccardo
authors.initials: AR
authors.lastname: Filippi
authors.forename: Paola
authors.initials: P
authors.lastname: Catuzzo
authors.forename: Angela
authors.initials: A
authors.lastname: Botticella
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ciammella
authors.forename: Pierfrancesco
authors.initials: P
authors.lastname: Franco
authors.forename: Valeria Casanova
authors.initials: VC
authors.lastname: Borca
authors.forename: Riccardo
authors.initials: R
authors.lastname: Ragona
authors.forename: Santi
authors.initials: S
authors.lastname: Tofani
authors.forename: Umberto
authors.initials: U
authors.lastname: Ricardi
mesh_terms: D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001940:Breast / Q000528:radiation effects; D017024:Chemotherapy, Adjuvant; D015331:Cohort Studies; D003287:Contrast Media; D005260:Female; D006321:Heart / Q000528:radiation effects; D006689:Hodgkin Disease / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000528:radiation effects; D015182:Lymphatic Irradiation / Q000379:methods; D008479:Mediastinal Neoplasms / Q000532:radiotherapy; D064847:Multimodal Imaging / Q000379:methods; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013961:Thyroid Gland / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media