Breast cancer: Does the risk of cardiac arrhythmias increase depending on the area irradiated?

France – Women treated for left breast cancer had a higher risk of arrhythmias after radiation. The risk of cardiac arrhythmias would be increased if the right atrium received a dose of radiation. However, no significant relationship has been demonstrated between the dose of radiation received by the heart as a whole or the ventricles (right or left) or left atrium and the risk of arrhythmias. In particular, the authors recommend monitoring the risk of arrhythmias, or cardiac arrhythmias, in women undergoing radiation therapy to the left breast.

Why is that important?

Adjuvant radiation therapy is often used after surgery for breast cancer. Exposure to radiation therapy (RT) is not without risk of complications, particularly cardiac, even several years after radiation. Coronary heart disease is the most common heart disease after radiation therapy for breast cancer. Studies show that they are more common after treatment for cancer on the left breast. Overall, the lifetime risk of coronary artery disease would increase by 7.4% for each additional Gy [1]. The risk of cardiac arrhythmias and, less commonly, conduction disorders (4-5% according to the literature) benefit from less research than coronary artery disease. Hence the interest of this study.

Principle results

Of the 116 women included, 21 cases of incident arrhythmia were reported. The mean age at RT was 64 years and the mean follow-up time since RT was 7.0 years.

The mean time between RT and the arrhythmia phenomenon was 4.3 years.

Whether women who developed an arrhythmia were more likely to have had a mastectomy, were receiving hormone therapy, were smokers, had high cholesterol, or had dyslipidemia compared to controls who did not develop the arrhythmia, these differences were not statistically significant.

The mean total dose to the heart was estimated at 0.97 Gy (higher for left breast than right breast cancer: 3.38 Gy versus 0.59Gy). The risk of developing abnormal heart rhythms was higher in women who had undergone RT for left breast cancer. On the other hand, neither the total dose absorbed by the heart nor the dose specifically absorbed by the right or left ventricle or the left atrium were associated with a significant increase in the risk of arrhythmias. Although not statistically significant, the radiation dose received by the right atrium was associated with an increased risk of arrhythmia (probability 1.19, p= 0.60), especially in cancers of the left breast (probability 1.76, p= 0.75). The authors therefore suggest that women treated for left breast cancer who have received radiation therapy to the right atrium should be more vigilant for the risk of cardiac arrhythmias and conduction disorders.

methodology

This case-control study is embedded in the multi-center MEDIRAD BRACE study with 347 cases of breast cancer (left or right). The population studied includes patients aged 40 to 75 who were followed up at the Pasteur Clinic in Toulouse between 2009 and 2013 and who underwent three-dimensional conformal radiotherapy (3D-CRT) after being diagnosed with breast cancer. on site or invasive, histologically proven. After surgery, all patients were treated with RT, including or without regional lymph node irradiation. The planned dose was most frequently 50 Gy in 25 daily portions of 2 Gy over 5 weeks, more rarely 32.5 Gy in 5 daily portions of 6 Gy.

This article was originally published on Univadis.fr, member of the Medscape network

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