ASTRO: Study Casts Doubt on Long-Term Heart Toxicity Risks of Breast Cancer Radiotherapy
“Over the past two decades, radiation therapy has become more precise and safer with modern techniques,” reported lead author Charles B. Simone II, MD, of the Hospital of the University of Pennsylvania in Philadelphia, and coauthors. “We are pleased to find that early stage breast cancer patients treated with modern radiation therapy treatment planning techniques do not have an increased risk of long-term cardiac toxicity and that breast conservation therapy (BCT) with radiation should remain a standard treatment option.”
The authors analyzed post-breast cancer-treatment medical records for 50 women with stage I and II breast cancer who had been randomized for treatment in the National Cancer Institute (NCI)'s Breast Conservation Trial during 1979 to 1987; of the women, 26 had undergone breast conservation therapy and 24 had undergone MRM.
Patients who underwent BCT had significantly lower ventricular mass than MRM patients (91 vs 110 gm; P=0.02), but the association fell to statistical nonsignificance after adjusting for systolic blood pressure, the authors reported. Patients who underwent MRM tended to have higher systolic blood pressures (139 mmHg vs 127 mmHg) and diabetes rates (12.5% vs 3.8%;P=0.27), but these trends were not statistically significant, the authors noted.
Myocardial infarctions occurred in two MRM patients and one MRM patient suffered heart failure, but Framingham 10-year myocardial infarction risk was similar overall (BCT 5.1% vs MRM 5.7%), the authors reported.
Diastolic function, including peak filling rate and diastolic volume recovery, were similar for MRM and BCT patients.
“Among BCT patients, cardiac structure and function were similar for right or left (breast) tumors,” the authors noted. Chemotherapy patients “tended toward more visible atherosclerosis,” (HR 2.4; P=0.07), Dr. Simone said.
“This is the first study to report comprehensive late cardiac outcomes after randomization for breast cancer therapy,” Dr. Simone said. “Based on this study, in the era of 3D planning, patients treated with breast radiotherapy do not have a higher risk of long-term cardiac morbidity compared with MRM patients.”