title: Impact of patient-specific factors, irradiated left ventricular volume, and treatment set-up errors on the development of myocardial perfusion defects after radiation therapy for left-sided breast cancer.
abstract: OBJECTIVE
  The aim of this study was to assess the impact of patient-specific factors, left ventricle (LV) volume, and treatment set-up errors on the rate of perfusion defects 6 to 60 months post-radiation therapy (RT) in patients receiving tangential RT for left-sided breast cancer.
  
  
  METHODS
  Between 1998 and 2005, a total of 153 patients were enrolled onto an institutional review board-approved prospective study and had pre- and serial post-RT (6-60 months) cardiac perfusion scans to assess for perfusion defects. Of the patients, 108 had normal pre-RT perfusion scans and available follow-up data. The impact of patient-specific factors on the rate of perfusion defects was assessed at various time points using univariate and multivariate analysis. The impact of set-up errors on the rate of perfusion defects was also analyzed using a one-tailed Fisher's Exact test.
  
  
  RESULTS
  Consistent with our prior results, the volume of LV in the RT field was the most significant predictor of perfusion defects on both univariate (p = 0.0005 to 0.0058) and multivariate analysis (p = 0.0026 to 0.0029). Body mass index (BMI) was the only significant patient-specific factor on both univariate (p = 0.0005 to 0.022) and multivariate analysis (p = 0.0091 to 0.05). In patients with very small volumes of LV in the planned RT fields, the rate of perfusion defects was significantly higher when the fields set-up "too deep" (83% vs. 30%, p = 0.059). The frequency of deep set-up errors was significantly higher among patients with BMI > or =25 kg/m2 compared with patients of normal weight (47% vs. 28%, p = 0.068).
  
  
  CONCLUSIONS
  BMI > or =25 kg/m2 may be a significant risk factor for cardiac toxicity after RT for left-sided breast cancer, possibly because of more frequent deep set-up errors resulting in the inclusion of additional heart in the RT fields. Further study is necessary to better understand the impact of patient-specific factors and set-up errors on the development of RT-induced perfusion defects.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Evans
authors.forename: Robert G
authors.initials: RG
authors.lastname: Prosnitz
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Yu
authors.forename: Su-Min
authors.initials: SM
authors.lastname: Zhou
authors.forename: Donna R
authors.initials: DR
authors.lastname: Hollis
authors.forename: Terence Z
authors.initials: TZ
authors.lastname: Wong
authors.forename: Kim L
authors.initials: KL
authors.lastname: Light
authors.forename: Patricia H
authors.initials: PH
authors.lastname: Hardenbergh
authors.forename: Michael A
authors.initials: MA
authors.lastname: Blazing
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Marks
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000532:radiotherapy*; D015897:Comorbidity; D005260:Female; D006801:Humans; D019300:Medical Errors / Q000706:statistics & numerical data*; D008875:Middle Aged; D009657:North Carolina / Q000453:epidemiology; D015995:Prevalence; D011832:Radiation Injuries / Q000453:epidemiology*; D020266:Radiotherapy, Conformal / Q000706:statistics & numerical data*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D017678:Sex Distribution; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000453:epidemiology*