Is there a dose-response relationship for heart disease with low-dose radiation therapy?

Int J Radiat Oncol Biol Phys. 2013 Mar 15;85(4):959-64. doi: 10.1016/j.ijrobp.2012.08.002. Epub 2012 Sep 27.

Abstract

Purpose: 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 and materials: 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.

Publication types

  • Clinical Trial, Phase II
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Breast Neoplasms / pathology
  • Breast Neoplasms / radiotherapy*
  • Coronary Vessels / physiopathology
  • Coronary Vessels / radiation effects
  • Dose-Response Relationship, Radiation
  • Female
  • Heart / diagnostic imaging
  • Heart / physiopathology
  • Heart / radiation effects*
  • Humans
  • Middle Aged
  • Multimodal Imaging
  • Myocardial Perfusion Imaging / methods*
  • Organs at Risk / diagnostic imaging
  • Organs at Risk / physiopathology
  • Organs at Risk / radiation effects*
  • Positron-Emission Tomography
  • Prospective Studies
  • Radiotherapy, Adjuvant / adverse effects
  • Radiotherapy, Adjuvant / methods
  • Radiotherapy, Conformal / adverse effects
  • Radiotherapy, Conformal / methods
  • Radiotherapy, Intensity-Modulated / adverse effects
  • Stroke Volume / physiology
  • Stroke Volume / radiation effects
  • Tomography, X-Ray Computed