Women who receive radiotherapy for breast cancer are at increased risk of cardiovascular disease, study results reveal.
“Irradiated breast cancer patients should be advised to refrain from smoking to reduce their risk for cardiovascular disease,” the researchers write in the Journal of the National Cancer Institute.
Dr Flora van Leeuwen from the Netherlands Cancer Institute in Amsterdam and colleagues studied the treatment-specific incidence of cardiovascular disease in 4,414 women who were treated for breast cancer between 1970 and 1986.
After a median follow-up of 18 years, 942 cardiovascular events were observed.
Women who underwent radiotherapy to either the left or right side of the internal mammary chain during 1970-79 were more likely to have a myocardial infarction (hazard ratio = 2.55, p<0.001), and congestive heart failure (HR = 1.72, p=0.002), than those women not treated with radiotherapy.
The risk of myocardial infarction declined over time among patients who received internal mammary chain radiotherapy after 1979, but the risk of congestive heart failure (HR = 2.66, p=0.01) and valvular dysfunction (HR = 3.17, p<0.001) remained increased.
Notably, patients who underwent radiotherapy plus adjuvant chemotherapy consisting of cyclosphosphamide, methotrexate, and fluorouracil after 1979 had a higher risk of congestive heart failure than patients who were treated with radiotherapy alone (HR = 1.85, p=0.002).
Furthermore, the additive effect of smoking and radiotherapy further increased the risk of myocardial infarction (HR = 3.04, p for departure from additivity = 0.039).
“We know from the medical records of patients in the study that irradiated patients were not routinely screened for cardiac symptoms,” the researchers note.
“Physicians should be still aware of the potentially increased risk of cardiovascular disease following specific radiotherapy regimens in long-term breast cancer survivors,” Dr van Leeuwen and coworkers said.
“More prolonged follow-up of large cohorts will be needed to further evaluate the long-term risks and benefits of modern adjuvant radiotherapy and chemotherapy for early breast cancer.”
J Natl Cancer Inst 2007;99:365-75