Coronary Artery Disease Caused by Radiation Exposure in Patients Battling Lung and Breast Cancer
In a significant breakthrough for cancer survivors who undergo thoracic radiation therapy, a multi-modality approach combining advanced hybrid imaging and specialized cardiac CT protocols is proving to be a game-changer in the early detection and comprehensive risk stratification of radiation-induced coronary artery disease (RI-CAD).
The cumulative incidence of RI-CAD is higher in women who undergo left-sided radiation compared to right-sided radiation, making early detection and management crucial.
One of the key imaging techniques in this fight against RI-CAD is PET/CT hybrid imaging. By combining metabolic information from PET with anatomical detail from CT, PET/CT offers improved accuracy in diagnosing RI-CAD. It can detect early functional changes in myocardial perfusion and metabolism, making it highly sensitive to microvascular disease from radiation.
Cardiac CT, including Coronary CT Angiography (cCTA), plays a pivotal role in assessing coronary anatomy, detecting coronary artery calcifications, and evaluating stent or graft patency. cCTA employs ECG-gating to synchronize image acquisition with the cardiac cycle, reducing motion artifacts and allowing high-resolution imaging at relatively low radiation doses.
Nonenhanced calcium scoring, a preliminary step in cardiac CT, quantifies coronary artery calcifications, a marker of atherosclerosis, which can be relevant in stratifying RI-CAD risk. Stress dynamic CT and combined CCTA protocols are being explored to add functional assessment to anatomical imaging, enhancing risk stratification.
In summary, PET/CT offers a combination of functional and anatomical data, detecting metabolic and perfusion abnormalities early. Coronary CT Angiography provides high-resolution anatomical visualization, calcium scoring, and includes dose-reduction protocols and ECG gating. Stress dynamic CT + CCTA adds functional workload assessment to anatomical imaging, potentially enhancing risk stratification by integrating ischemia assessment with anatomical data.
This multi-modality approach allows for earlier identification of RI-CAD, both subclinical and clinically significant, facilitating timely intervention and management to reduce adverse cardiac outcomes. It maximises sensitivity and specificity while optimising radiation doses and patient safety.
It's important to note that no single modality is definitive alone. A combination of PET/CT functional imaging with high-resolution coronary CT angiography offers the best clinical pathway for early detection and comprehensive risk stratification of RI-CAD.
18F-Fluorodeoxyglucose (FDG) is a widely used PET tracer for identifying inflammation within the large or major arteries such as the aorta and the myocardium. PET, particularly when combined with CT, offers additional functional insight and can assess myocardial perfusion and viability.
Radiation therapy is a key component in the treatment of lung and breast cancers. Coronary artery disease is the most common adverse cardiac effect caused by radiation therapy, with a prevalence of up to 85%. Damage from radiation-induced CAD progresses slowly, often manifesting years to decades after initial therapy.
The pathophysiology of radiation-induced CAD involves oxidative damage to proteins, DNA, and lipids. The radiation dose to the heart from left-sided breast cancer is more than double that of right-sided radiation. In a study of stage I-II patients with breast cancer treated with radiation therapy, abnormalities were found in 59% of left-side irradiated patients compared to just 8% of right-side patients.
The risk of major coronary events increases linearly with the mean heart dose of thoracic radiation in women with breast cancer, with risk continuing for at least 20 years after exposure. Left ventricular segments are particularly sensitive to radiation exposure.
This innovative approach in the field of medical imaging is set to revolutionise the management of cancer survivors, ensuring timely intervention and improved patient outcomes.
In this context of medical imaging advancements, the combination of PET/CT functional imaging and high-resolution coronary CT angiography is essential for the early detection and comprehensive risk stratification of radiation-induced coronary artery disease (RI-CAD), a common adverse cardiac effect in cancer survivors who undergo radiation therapy, especially for those with left-sided radiation. This approach not only helps in the early identification of RI-CAD but also contributes to health-and-wellness, cardiovascular-health, and the management of medical-conditions in cancer survivors.
