Reassurance on risk of radiation-induced cardiac disease


Women with breast cancer who receive radiation therapy delivered with contemporary techniques do not appear to be at risk of cardiac dysfunction or injury in the first year following treatment.

The study, from the Austin Hospital, enrolled 20 chemotherapy-naive women with left-sided breast cancer who received a mean heart dose of 1.3 ± 0.7 Gy from their radiation therapy.

The study found no difference on echocardiographic parameters, including left ventricular ejection fraction and global longitudinal strain, from baseline to the end of treatment and at a 12-month follow-up.

Similarly, there was no change in biomarkers such as high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-hormone brain natriuretic peptide (NT-proBNP) from baseline to the conclusion of the study.

The study, published as a Research Letter in JACC: CardioOncology said they found no evidence of subclinical myocardial dysfunction or injury during and up to 12 months post-RT.

“This suggests that RT delivered with contemporary techniques is not associated with early cardiac sequelae. Larger studies are needed to further verify this hypothesis and establish the long-term risks of radiation-induced heart disease (RIHD).”

Lead author Dr Alexandra Murphy told the limbic most of the understanding of radiation-induced heart disease came from older trials where treatment meant mean heart doses of 3Gy and greater.

“From a breast cancer perspective, we are now using very targeted contemporary techniques such as deep inspiration breath holding and stereotactic techniques where they really are focussing right down on the tumours. That has hugely affected the amount of radiation that is impacting the heart,” she said.

She said a strength of the study was isolating a chemotherapy-naive population.

“The important thing about this study in particular was we focussed on a group of patients that were not receiving any other potentially cardiotoxic systemic therapies. So this is by definition an incredibly low risk population from a cancer perspective.”

“To come out of this and show that with contemporary measures we are not seeing any early signal of myocardial damage, that is really important for the medical oncologists and the radiation oncologists to say this is an appropriate therapy, it is okay to treat these people especially younger women.”

She said it was very reassuring particularly as more women were diagnosed earlier and younger, and radiation therapy had an important role in managing localised disease.

“If we can over time, exclude this [RHID] and say that contemporary radiation techniques limit this cardiotoxicity then we can probably also save on unnecessary investigations from a cardiology perspective in the future.”

Dr Murphy, from the department of cardiology at Austin Health, said the potential risks of cardiotoxicity from anthracyclines, herceptin and chest radiotherapy were well known in women with breast cancer.

“We know though that of those three, the more you have the more likely you are to develop cardiotoxicity. But it doesn’t end there. What I personally find really interesting is the literature showing the multiplicative effect of traditional cardiovascular risk factors on the development of RIHD.”

“So if you have high blood pressure, if you have high cholesterol, if you are a smoker or if you have a family history of heart disease, all of that has a logarithmic effect on your risk of developing RIHD down the track.”

“If we now understand that the women who develop the heart problems down the track are the ones who had poorly controlled cardiovascular risk factors at the start, we must now think of ways to tackle that. We cannot ignore traditional cardiovascular risk factors in women undergoing breast cancer treatment.”

Dr Murphy is currently trialling a smart phone app which can help women with breast cancer manage their cardiovascular risk factors.

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