title: Is there a dose-response relationship for heart disease with low-dose radiation therapy?
abstract: OBJECTIVE
  To quantify cardiac radiation therapy (RT) exposure using sensitive measures of cardiac dysfunction; and to correlate dysfunction with heart doses, in the setting of adjuvant RT for left-sided breast cancer.
  
  
  METHODS
  On a randomized trial, 32 women with node-positive left-sided breast cancer underwent pre-RT stress single photon emission computed tomography (SPECT-CT) myocardial perfusion scans. Patients received RT to the breast/chest wall and regional lymph nodes to doses of 50 to 52.2 Gy. Repeat SPECT-CT scans were performed 1 year after RT. Perfusion defects (PD), summed stress defects scores (SSS), and ejection fractions (EF) were evaluated. Doses to the heart and coronary arteries were quantified.
  
  
  RESULTS
  The mean difference in pre- and post-RT PD was -0.38% ± 3.20% (P=.68), with no clinically significant defects. To assess for subclinical effects, PD were also examined using a 1.5-SD below the normal mean threshold, with a mean difference of 2.53% ± 12.57% (P=.38). The mean differences in SSS and EF before and after RT were 0.78% ± 2.50% (P=.08) and 1.75% ± 7.29% (P=.39), respectively. The average heart Dmean and D95 were 2.82 Gy (range, 1.11-6.06 Gy) and 0.90 Gy (range, 0.13-2.17 Gy), respectively. The average Dmean and D95 to the left anterior descending artery were 7.22 Gy (range, 2.58-18.05 Gy) and 3.22 Gy (range, 1.23-6.86 Gy), respectively. No correlations were found between cardiac doses and changes in PD, SSS, and EF.
  
  
  CONCLUSIONS
  Using sensitive measures of cardiac function, no clinically significant defects were found after RT, with the average heart Dmean <5 Gy. Although a dose response may exist for measures of cardiac dysfunction at higher doses, no correlation was found in the present study for low doses delivered to cardiac structures and perfusion, SSS, or EF.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109-5010, USA.
authors.forename: Eugene
authors.initials: E
authors.lastname: Chung
authors.forename: James R
authors.initials: JR
authors.lastname: Corbett
authors.forename: Jean M
authors.initials: JM
authors.lastname: Moran
authors.forename: Kent A
authors.initials: KA
authors.lastname: Griffith
authors.forename: Robin B
authors.initials: RB
authors.lastname: Marsh
authors.forename: Mary
authors.initials: M
authors.lastname: Feng
authors.forename: Reshma
authors.initials: R
authors.lastname: Jagsi
authors.forename: Marc L
authors.initials: ML
authors.lastname: Kessler
authors.forename: Edward C
authors.initials: EC
authors.lastname: Ficaro
authors.forename: Lori J
authors.initials: LJ
authors.lastname: Pierce
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D003331:Coronary Vessels / Q000503:physiopathology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000528:radiation effects*; D006801:Humans; D008875:Middle Aged; D064847:Multimodal Imaging; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000528:radiation effects*; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects; D013318:Stroke Volume / Q000502:physiology / Q000528:radiation effects; D014057:Tomography, X-Ray Computed