Some older breast cancer treatments associated with increased risk of cardiovascular disease

Some breast cancer survivors who received certain types of radiotherapy and chemotherapy in the past, are at an increased risk of developing heart disease as a result of their cancer treatment, a new study has found.

According to the research by clinicians from the Netherlands Cancer Institute in Amsterdam, both radiotherapy and anthracycline-based chemotherapy are commonly used and highly effective breast cancer treatments. Unfortunately, however they have also been associated with increased risk of cardiovascular disease.

For the study researchers assessed the incidence of cardiovascular disease including ischaemic heart disease (IHD), heart failure (HF) and valvular heart disease in more than 14,000 Dutch breast cancer patients aged under 62, who were treated for breast cancer between 1970 and 2009.

The researchers explained that between 1970 and 2009, irradiation of the lymph nodes behind the sternum or chest known as IMC-irradiation, exposed the heart to high doses of radiation. The study revealed that this dose of radiation was associated with an increased rate of cardiovascular disease compared to women who received the lowest cardiac doses.

In patients with an established cardiovascular risk factors such as smoking or high blood pressure, the 20-year incidence of ischemic heart disease was 11 per cent in patients with IMC-irradiation compared to 6 per cent in those who did not have these risk factors. The study also found that anthracycline-based chemotherapy was associated with a four-fold increased rate of heart failure and combined with IMC-irradiation there as a substantial, nine-fold increased rate.

However, the researchers noted that the radiation techniques used today expose the heart to lower doses, and therefore the risk of radiation-associated cardiovascular disease are expected to be lower in patients treated today. For most women the benefits of treating their cancer will also outweigh the risks they added.

“However, the risks may be greater for some subgroups, e.g. women with left-sided breast cancer who receive both IMC irradiation and anthracycline-based chemotherapy or who have cardiovascular risk factors. For breast cancer survivors, our results are also relevant as subgroups may benefit from cardiac surveillance,” the researchers concluded

Commenting on the study Dr Angie Brown, Medical Director of the Irish Heart Foundation said it confirmed other studies that showed previous treatment for breast cancer that included radiotherapy and anthracycline chemotherapy increases the risk of developing coronary heart disease, valvular heart disease and heart failure. It also confirmed that the presence of cardiovascular risk factors prior to radiotherapy increases the absolute risk of developing coronary artery disease.

Dr Brown explained, “For women who receive breast cancer treatment today, the predicted absolute risks of treatment are expected to be substantially lower than for the women in this study. This is partly because the risk of ischaemic heart disease in the general population has decreased since the 1970s. Furthermore, modern radiotherapy techniques use much lower doses of radiotherapy and chemotherapy regimens have been modified and patients are closely monitored for evidence of cardiac damage with treatment modification as appropriate.”

“This study indicates that these patients should have routine risk factor assessment and be given advice and treatment as appropriate for any cardiac risk factors that are identified, some BC survivors may benefit from cardiac surveillance as disease can develop many years after treatment.”

This study was published recently in the British Journal of Cancer (2018)