title: Cardiac dosimetry for adjuvant left-sided breast radiotherapy: patterns with 2D- versus 3D-era planning and correlates of coronary dose with maximum depth of myocardial exposure.
abstract: BACKGROUND
  The purpose of this study was to evaluate the cardiac dosimetry delivered before and after routine 3D CT whole-breast radiotherapy planning, including cardiac contouring and the relevance of a 15-mm maximum myocardial depth (MMD) planning tolerance threshold.
  
  
  METHODS
  The PULp FICTion study permitted cardiac dosimetry comparisons for 140 patients (70 in the 'before-contouring era' (BC) and 70 in the 'post-contouring era' (PC) ). Comparisons were made of MMD and dosimetry for whole heart, anterior myocardium and left anterior descending (LAD)/coronary artery (overall, superior and inferior) by contouring era.
  
  
  RESULTS
  The MMD mean was 15.6 mm (range 1-40). If the internal mammary chain (IMC) was treated, the MMD increased from 15 to 27.7 mm (P < 0.0001). Excluding IMC patients revealed no difference in MMD between conservation and mastectomy (14.9 vs 17.4, P = 0.3), boost and no boost (14.5 vs 15.5, P = 0.41) or BC and PC (15.7 vs 14.5. P = 0.33) and no differences related to treating clinician, anthracycline use or age. Only in potentially low-risk patients defined as not requiring IMC or boost treatment was there a difference in MMD by era, with 17.7 mm (1-40) in the BC era and 13.9 mm (1-31) mm in the PC era (P = 0.013). Inferior LAD mean doses increased from 49% to 84% of the prescribed breast dose when MMD was >15 mm, and the proportion of patients with a mean dose <40% of the prescribed breast dose fell from 48% to 8%.
  
  
  CONCLUSIONS
  Changes in cardiac dosimetry associated with routine cardiac contouring have initially been minor and restricted to low-risk patients. A 15-mm MMD reasonably represents a transition from low mean distal LAD doses to substantial doses.
authors.affiliation: Cancer Care Centre, St George Hospital, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Ph
authors.initials: P
authors.lastname: Graham
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001822:Body Burden; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006335:Heart Injuries / Q000209:etiology / Q000517:prevention & control*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects / Q000379:methods; D013223:Statistics as Topic; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
keywords: adjuvant; breast; coronary; dosimetry; radiotherapy