Breast Cancer

SS 12 - Breast 1 - Toxicity

91 - Comparing Whole Heart Versus Coronary Artery Dosimetry in Predicting the Risk of Cardiac Toxicity Following Breast Radiation Therapy

Monday, October 22
12:05 PM - 12:15 PM
Location: Room 214 C/D

Comparing Whole Heart Versus Coronary Artery Dosimetry in Predicting the Risk of Cardiac Toxicity Following Breast Radiation Therapy
S. A. Patel1, S. Mahmood2, T. Nguyen3, B. Y. Yeap4, R. B. Jimenez5, N. M. Meyersohn6, T. G. Neilan3, and S. MacDonald7; 1Harvard Radiation Oncology Program, Boston, MA, 2Divison of Cardiology, Massachusetts General Hospital, Boston, MA, 3Massachusetts General Hospital, Boston, MA, 4Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 5Department of Radiation Oncology, Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA, 6Department of Radiology, Massachusetts General Hospital, Boston, MA, 7Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA

Purpose/Objective(s): Prior localization studies have implicated accelerated left anterior descending artery (LAD) atherosclerosis in the development of radiation-induced heart disease following breast radiation therapy (RT). However, whole heart dose constraints, namely mean heart dose (MHD), are most commonly utilized in RT treatment planning to predict and avoid cardiac toxicity. This study compares the relationship between MHD and LAD maximum dose (Dmax) to the onset of coronary artery disease identified on CT angiogram (CTA).

Materials/Methods: We identified 52 women with stage I-III breast cancer (36 left, 16 right) treated with adjuvant breast or chest wall 3-dimension conformal RT who subsequently underwent CTA. No cardiac substructural dose constraints were used at treatment, and coronary vessels were contoured retrospectively and reviewed by a cardiac radiologist. Dosimetry to the LAD was calculated based on the individual RT plan used for treatment. A nested case-control study of incident LAD stenosis ≥ 25% luminal involvement and coronary artery calcification (CAC) using Agatston score was conducted. Controls were matched to cases on elapsed years between RT and CTA. Odds ratios (OR) were calculated using conditional logistic regression to assess the attribution of LAD Dmax and MHD dose parameters, adjusting for Atherosclerotic Cardiovascular Disease (ASCVD) score, history of ischemic heart disease, and statin use.

Results: The median follow-up time from RT to CTA was 5.1 years (range, 2.5-18.1). LAD Dmax was more strongly associated with the onset of any CAC (Agatston score ≥1), moderate/severe CAC (Agatston score ≥101), and LAD stenosis (≥25% lumen). For any CAC, OR was 1.15 (95% CI 0.99-1.33, p=0.06) and 2.21 (95% CI 1.13-5.03, p=0.02) for MHD and LAD Dmax, respectively. For moderate/severe CAC, OR was 1.04 (95% CI 0.95-1.23, p=0.24) and 2.57 (95% CI 1.01-7.04, p=0.04) for MHD and LAD Dmax, respectively. For LAD stenosis, OR was 1.21 (95% CI 1.01-1.46, p=0.04) and 4.85 (95% CI 1.42-16.63, p=0.01) for MHD and LAD Dmax, respectively. LAD Dmax > 10 Gy was a significant threshold for increased odds of developing any CAC (OR 10.21, 95% CI 1.42-21.83, p=0.03), moderate/severe CAC (OR 5.21, 95% CI 1.16-18.36, p=0.04), and LAD stenosis (OR 6.52, 95% CI 1.39-19.67, p=0.03).

Conclusion: Compared to MHD, LAD Dmax had a stronger association with the onset of CAC and LAD stenosis identified on CTA. The LAD should be more routinely included as an avoidance structure for breast RT planning, and if confirmed on prospective analysis, a Dmax threshold of 10 Gy may serve as a useful clinical parameter to minimize late cardiac toxicity.

Author Disclosure: S.A. Patel: None. T. Nguyen: None. R.B. Jimenez: None. N.M. Meyersohn: None. T.G. Neilan: None.

Sagar Patel, MD

Harvard Radiation Oncology Program

Disclosure:
No relationships to disclose.

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91 - Comparing Whole Heart Versus Coronary Artery Dosimetry in Predicting the Risk of Cardiac Toxicity Following Breast Radiation Therapy



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