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Type of breast cancer irradiation linked to risk for CVD
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Women with early-stage breast cancer who received left-sided radiotherapy in a supine position appear to be at elevated risk for CVD, according to a research letter published in JAMA Internal Medicine.
The excess risk was highest for those with high cardiac risk factors at baseline, including MI, coronary revascularization, ischemic stroke or death from ischemic heart disease.
David J. Brenner, PhD, DSc, of Columbia University Medical Center, and colleagues calculated the association between coronary events and radiation treatment factors such as mean cardiac dose, cardiac risk, treatment side and body positioning. They prospectively generated radiation treatment plans of 48 patients with stage 0 through IIA breast cancer treated at the New York University Department of Radiation Oncology after 2005.
Lifetime radiation-associated excess risk for a major cardiac event (MI, coronary revascularization or death from ischemic heart disease) was calculated based on treatment side, radiotherapy position and mean cardiac dose of radiation.
Mean cardiac doses were 2.17 Gy for left-sided radiotherapy in a supine position, 1.03 Gy for left-sided radiotherapy in a prone position, 0.62 Gy for right-sided radiotherapy in a supine position and 0.64 Gy3 for right-sided radiotherapy in a prone position.
Excess risk ratios were as follows:
- For left-sided radiotherapy in a supine position: 0.22 (95% CI, 0.08-0.36) for patients with low baseline risk, 0.42 (95% CI, 0.14-0.7) for patients with medium baseline risk and 3.52 (95% CI, 1.47-5.85) for patients with high baseline risk.
- For left-sided radiotherapy in a prone position: 0.09 (95% CI, 0.05-0.13) for patients with low baseline risk, 0.17 (95% CI, 0.09-0.25) for patients with medium baseline risk and 1.31 (95% CI, 0.86-1.86) for patients with high baseline risk.
- For right-side radiotherapy in a supine position: 0.05 (95% CI, 0.03-0.07) for patients with low baseline risk, 0.1 (95% CI, 0.06-0.14) for patients with medium baseline risk and 0.79 (95% CI, 0.57-1.06) for patients with high baseline risk.
- For right-sided radiotherapy in a prone position: 0.06 (95% CI, 0.03-0.08) for patients with low baseline risk, 0.11 (95% CI, 0.05-0.16) for patients with medium baseline risk and 0.84 (95% CI, 0.57-1.18) for patients with high baseline risk.
“Because the effects of radiation exposure on cardiac disease risk seem to be multiplicative, the highest absolute radiation exposure risks correspond to the highest baseline cardiac risk,” Brenner and colleagues wrote. “Consequently, radiotherapy-induced risks of major coronary events are likely to be reduced in these patients by targeting baseline cardiac risk factors (cholesterol, smoking, hypertension), by lifestyle modification and/or by pharmacological treatment.”
Disclosure: The researchers report no relevant financial disclosures.
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