title: Radiation during deep inspiration allows loco-regional treatment of left breast and axillary-, supraclavicular- and internal mammary lymph nodes without compromising target coverage or dose restrictions to organs at risk.
abstract: OBJECTIVE
  Loco-regional radiotherapy of left-sided breast cancer represents a treatment planning challenge when the internal mammary chain (IMC) lymph nodes are included in the target volume. This treatment planning study evaluates the reduction in cardiopulmonary doses when radiation is given during deep inspiration breath-hold (DIBH). This was achieved without compromising dose coverage to the planning target volume (PTV).
  
  
  METHODS
  Seventeen patients with early breast cancer, referred for adjuvant radiotherapy, were included. For each patient two computed tomography (CT)-scans were acquired; the first during free breathing (FB) and the second during DIBH. The scans were monitored by the Varian RPM respiratory gating system. Audio-visual guidance was used. The treatment planning of the two CT studies was performed focusing on good coverage (V95% > 98%) of the PTV. Doses to the heart, left anterior descending (LAD) coronary artery, lungs and contralateral breast were assessed.
  
  
  RESULTS
  With equal PTV coverage, average mean heart dose was reduced from 6.2 Gy to 3.1 Gy in DIBH plans as compared to FB. Average volume receiving 25 Gy or more (V25Gy) was reduced from 6.7% to 1.2%, and the number of patients with V25Gy > 5% was reduced from 8 to 1 utilizing DIBH. The average mean dose to the LAD coronary artery was reduced from 25.0 Gy to 10.9 Gy. The average ipsilateral lung volume receiving 20 Gy or more (V20Gy) was reduced from 44.5% to 32.7% with DIBH. In 11 of the DIBH plans V20Gy was lower than 35%, in accordance with national guidelines, while none of the FB plans fulfilled this recommendation.
  
  
  CONCLUSIONS
  Respiratory gated radiotherapy during DIBH is a suitable technique for loco-regional breast irradiation even when IMC lymph nodes are included in the PTV. Cardiopulmonary doses are considerably decreased for all dose levels without compromising the dose coverage to PTV.
authors.affiliation: Department of Hematology and Oncology, Stavanger University Hospital, Stavanger, Norway. hjem@sus.no
authors.forename: Mari H B
authors.initials: MH
authors.lastname: Hjelstuen
authors.forename: Ingvil
authors.initials: I
authors.lastname: Mjaaland
authors.forename: Johan
authors.initials: J
authors.lastname: Vikström
authors.forename: Kjell Ivar
authors.initials: KI
authors.lastname: Dybvik
mesh_terms: D000328:Adult; D000368:Aged; D001365:Axilla; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects*; D008875:Middle Aged; D058958:Organs at Risk; D011379:Prognosis; D011832:Radiation Injuries / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D014057:Tomography, X-Ray Computed