The volume of the left ventricle receiving 5 Gy (LV-V5) during radiotherapy (RT) predicted an increased risk of acute coronary events (ACE) among patients with breast cancer, according to a study published in the Journal of Clinical Oncology.1

A prior study demonstrated mean heart dose (MHD) of RT to the entire heart had a dose-response relationship with the rate of major ACE with a relative increase of 16% per Gy within the first 9 years.2 This study sought to validate these findings and identify other dose-distribution parameters that may better predict ACE.

The single-center study included 910 consecutive female patients with stage I to III invasive adenocarcinoma or carcinoma in situ who received RT after breast-conserving surgery.

During a median follow-up time of 7.6 years (range, 0.1 to 10.1 years), the MHD was 2.37 Gy (range, 0.51 to 15.25 Gy) and the cumulative incidence of ACE rose by 16.5% per Gy (95% CI, 0.6-35.0; P = .042).1

LV-V5 demonstrated the largest difference in ACE incidence between cases and non-cases for different cardiac substructures and was significantly associated with the cumulative incidence of ACE using univariable Cox regression analysis (hazard ratio [HR], 1.016; 95% CI, 1.002-1.030; P = .016).

The c-statistic of the MHD-based normal tissue complication probability (NTCP) model was 0.79 (95% CI, 0.71-0.87), and improved to 0.80 (95% CI, 0.72-0.88) when MHD was replaced with LV-V5 (HR, 1.017; 95% CI, 0.999-1.035; P = .041).

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The investigators indicated these data independently validate the MHD-based NTCP model for ACE among patients with BC treated with RT. The model could be improved by replacing MHD with LV-V5, but further validation studies are required.

References

  1. van den Bogaard VAB, Ta BDP, van der Schaaf A, et al. Validation and modification of a prediction model for acute cardiac events in patients with breast cancer treated with radiotherapy based on three-dimensional dose distributions to cardiac substructures. J Clin Oncol. 2017 Jan 17. doi: 10.1200/JCO.2016.69.8480 [Epub ahead of print]
  2. Darby SC, Ewertz M, McGale P, et al. Risk of ischemic heart disease in women after radiotherapy for breast cancer. N Engl J Med. 2013;368:987-98. doi: 10.1056/NEJMoa1209825