Cancer Treatment and Heart Disease
Cancer treatment with chemotherapy and or radiotherapy can have adverse effects on the heart and circulation, both during treatment and for years afterwards.
Improved results of cancer treatment mean more patients are surviving long-term when heart disease, caused or worsened by this treatment, may affect both quality of life and life expectancy. For example, cancer heart disease is still the major cause of death in women over 65 with early stage breast cancer.
Detecting and reducing the impact of cancer treatment on the heart and circulation is a major emerging collaboration between cancer specialists – Oncologists, Radiotherapists, Surgeons – and Cardiologists, called ‘Cardio-Oncology’.
Central Sydney Cardiology is collaborating with our colleagues in cancer medicine at Lifehouse (http://www.mylifehouse.org.au/), Royal Prince Alfred and Strathfield Private Hospitals, as part of our commitment to bringing the best of current clinical research into clinical practice.
How Cancer Treatment affects the Heart and Blood Vessels
Radiation treatment is designed to damage tumours but also affects healthy tissues in the field of radiation. In the case of tumours in the chest, radiation can damage not only the heart itself but also the major blood vessels including the coronary arteries.
Chemotherapy treatments are distributed by the heart and circulatory system exposing these healthy tissues to their effects too.
Cancer treatments have many different ways in which they affect heart and blood vessel function including:
Adverse effects of cancer treatment may be transient or reversible by appropriate treatment, or may be permanent but the impact can be reduced by treatment. Individual cancer treatments have different effects on the heart so surveillance programs need to be tailored to the individual needs of the patient.
Several classes of commonly used chemotherapy agents are known to lead to myocardial dysfunction and heart failure. These include:
Although this is a rapidly changing landscape, it is clear that the toxic effects of a variety of chemotherapy agents on the heart and circulation can be detected before they are clinically obvious and treated using readily available treatments for heart disease such as angiotensin converting enzyme (ACE) inhibitors, angiotensin 2 receptor blockers (ARBs) and beta-blockers.
Our previous understanding of cardiotoxity of chemotherapy agents was that some agents were probably safe and others had dose-related effects which could be managed. It is now clear that the relationship between chemotherapy treatment and heart function is much more complex. It was thought that for drugs such as anthracyclines that there is a ‘safe’ dose but more sensitive ways of detecting heart disease suggest that the safety threshold may be lower or not actually exist.
Recent improvements in early detection of heart muscle damage
The key advance in our understanding of this area is that patients treated for cancer need careful lifetime follow up to detect and treat heart and blood vessel disease before it affects their health.
Standard echocardiograms, exercise stress tests, CT scans and MRIs are very good at detecting effects on arteries and valves due to cancer treatment but are not very good at detecting heart muscle damage before it is clinically obvious and when it is potentially most responsive to treatment.
Heart failure is a very serious consequence of some chemotherapy treatments.
Currently widely used imaging methods like 2Dechocardiograms or Gated Heart Pool Scans (nuclear medicine measurements of left ventricular function – ejection fraction or LVEF) are not very good at detecting heart muscle damage when left ventricular function is normal or only mildly reduced.
The result is that there may have been irreversible heart muscle (myocardial) damage before a change in function can be detected using conventional imaging methods. This is particularly true of newer treatments for breast cancer like Herceptin for example.
However, recent developments in echo – 3D echo and strain imaging – allow early detection of heart damage and early treatment has been shown to reverse it.
3D echo and Strain Imaging in Chemotherapy Induced Heart Disease
Cardiac ultrasound is safe, relatively painless, does not involve radiation exposure and is well tolerated. A major advance in ultrasound has been 3D echo which combines a series of standard 2D pictures to create a 3D image but then looks at how selected parts of the heart change in real time as the heart beats, known as ‘4D’ ultrasound. 3D imaging is substantially better than 2D echo, adding MRI like accuracy in assessment of cardiac function without the cost and availability limits of cardiac MRI. 3D echo has the added benefit of simplified strain measurements and more accurate assessment of serial changes in left ventricular function than 2D echo.
This new technology of 3D and 4D ultrasound will greatly enhance the accuracy of surveillance programs for heart disease in cancer patients.
Other Methods of Early Detection of Chemotherapy Induced Heart Disease
Currently available blood markers of cardiac injury (Troponins, TnI or TnT) and dysfunction (brain natriuretic peptide or BNP) have been used in combination with echo measurements of left ventricular function (EF) and Strain imaging (2D and 3D).
‘The use of simple biomarkers such as troponins and BNP should be strongly considered but is not a substitute for objective evaluation by echocardiography or similar modalities.’(Position statement from the Heart Failure Association of the European Society of Cardiology 2011).
Although modern radiotherapy is designed to target cancers more accurately while minimising damage to normal tissues in the field of radiation, it remains a major risk factor for atherosclerosis (artery disease) in any blood vessels in the radiation field. There are many ways of screening for aortic or coronary artery disease which include echocardiograms, exercise stress tests and CT scans.
Radiation injury can also occur to the heart valves and the tissue around the heart (pericardium). Standard echocardiograms will detect valve disease reliably and is readily available.
Damaged blood vessels are prone to blood clotting or thrombosis. Patients with cancer are often more likely to have blood clotting or thrombosis so the combination of radiotherapy and the underlying disease is a major risk factor for blood vessel disease and its complications.
Current best practice involves intensive treatment of risk factors for heart disease and stroke in cancer patients combined with screening for asymptomatic carotid, aortic or coronary artery disease. These patients should be followed up regularly to look for the development of heart and blood vessel disease.
General Measures to Improve the Heart Health of Patients Treated for Cancer
Current research clearly shows that heart disease risk factors may worsen during the course of cancer treatment. Women with breast cancer are more likely to suffer from heart disease than women with the same risk factor profile who have not had breast cancer.
While a primary focus on cancer treatment is clearly important, there are important lifestyle changes which can be made to reduced future risk of heart disease. For example, women treated for breast cancers often gain weight, many become more sedentary, and measured fitness levels are often reduced. These are well known, modifiable, risk factors for heart disease.