By Nancy Keene and Dr. Kevin Oeffinger MD
Important: This article appears in the Winter 2000 Candlelighters Childhood Cancer Foundation Newsletter (downloadable as a pdf file on the Candlelighters web site). It is reproduced here with the permission of Ruth Hoffman, Executive Director and Newsletter Editor of CCCF.
In our last column, we discussed the long-term effect anthracyclines (adriamycin, daunorubicin, idarubicin) can have on the heart. Several readers called asking about the recommendation for life-long follow up for those who received 175 mg/m2 after the age of five. This dosage refers to the total dose a survivor received during treatment. The summary of treatment that you should get from the treating institution should include total (also called cumulative dose) of every medication you received. So, if you received 175 mg/m2 of any combination of anthracyclines over the course of your treatment after the age of five (or any dose prior to the age of five) you should get periodic testing of your heart for the rest of your life. Lower dosages generally do not cause a problem. Nevertheless, because some survivors will have heart problems even with lower dosages, it is important for them to continue regular medical follow-up with a physician or a long-term follow-up program and discuss screening tests on an individual basis.
Like anthracyclines, high-dose radiation can cause several late effects to the heart. Use of radiation has made a tremendous difference in treating cancer and leading to significantly higher survival rates, but can also lead to problems many years after treatment. Because some survivors are at higher risk for heart problems than others and because tests are available that can pick up problems at an early stage, it is important for each survivor to find out his/her individual risk.
As we discussed in Part I, the heart is a large muscle that is divided into four chambers and is designed to pump the blood around the body. The upper chambers or rooms are called atria and the lower chambers are called ventricles. The blood returning from the body enters the right atrium, is squeezed into the right ventricle, and then is pumped into the blood vessels in the lungs. It is here that the oxygen we breathe is transferred into many small blood vessels in the lungs. The blood, now rich with oxygen, returns to the left atrium and then is squeezed into the left ventricle, the largest and most powerful of the chambers. The left ventricle contracts to circulate the blood to the entire body.
The doors between the heart chambers are called valves (aortic, mitral, pulmonary, and tricuspid). One valve will open as blood flows into a chamber and then close as the chamber contracts and squeezes the blood into the next chamber. On the outside of the heart is a network of blood vessels (coronary arteries) that take oxygen and nutrients to the hard working heart muscle. This network starts as two vessels that then divide into several branches.
The Problem with Radiation
Most survivors who received radiation will not have a problem with their heart. But in some, the radiation can damage the heart in one of several ways, including damaging the heart muscle, the valves, or the coronary arteries. Each of these three problems is quite different, so let's discuss them one at a time.
Damage to the heart muscle is called cardiomyopathy. Remember from our last column that this term is used when the muscle does not work as well as it should. It generally affects the left ventricle (chamber) more than other parts of the heart, causing it to be stiff and less responsive to changes. Usually when someone is at rest the heart does not have to work hard. But when the heart needs to work harder, such as during pregnancy or strenuous physical activity, the stiff left ventricle may not be capable of increased pumping action. If this happens, the blood that is being pumped through the left side of the heart (atrium and ventricle) does not get pumped out fast enough and some of it backlogs in the small blood vessels of the lungs. The oxygen in the lungs is transferred to these small blood vessels, and so when the vessels become engorged with the backlogged blood, the oxygen can not be transferred properly. Though this problem, called congestive heart failure, can be quite serious, there are medications that can help.
Radiation can also damage the valves in the heart, especially the two valves on the left side of the heart (mitral and aortic). If a valve is damaged, it can lead to either being "leaky" so that blood flows backwards into the chamber it came from or it can be stiff and not open very well, slowing the flow of blood. This can lead to congestive heart failure and other problems with the heart.
A third problem that radiation can cause is premature coronary artery disease. The network of small blood vessels on the outside of the heart feed the heart muscle with oxygen and nutrition. The interiors of healthy blood vessels are smooth. Radiation can roughen the inside of blood vessels. These rough spots provide a site for fatty deposits (plaques) to develop in coronary arteries and other arteries and veins. Calcium deposits can harden the plaques resulting in atherosclerosis (hardening of the arteries).
Coronary artery disease (coronary = heart, artery = blood vessel, disease = what we don't want) is when one or more of the blood vessels or branches gets clogged with plaque. It is similar to a clogged pipe that does not allow much to flow by it. If this happens, the heart muscle cannot get enough oxygen and nutrition for all of its work. So when the heart needs to work harder and it cannot get enough oxygen or nutrition, it generally causes some chest pain (angina) which will last a few minutes until the oxygen gets gets through the partially clogged artery. If the blood vessel is fully blocked, the part of the muscle that was depending upon the oxygen from that vessel dies (a heart attack). If it is a small branching blood vessel going to a small amount of heart muscle, then the person has a small or minor heart attack. But if it is a larger vessel feeding a larger amount of heart muscle, the heart attack is serious and can be life-threatening.
Who is at risk?
Children or teens who received spinal radiation, chest radiation (Hodgkins, non-Hodgkins lymphoma), left flank (Wilms), or radiation directly to the heart are possibly at risk. Modern radiation techniques using lower total doses, hyperfractionation (smaller doses more often), and cardiac shielding are less likely to cause damage.
Whether the heart sustains injury after radiation treatment depends on several factors including:
What are the symptoms of a heart problem from radiation?
The signs and symptoms for radiation-induced heart damage vary widely. Possible symptoms of congestive heart failure include:
Possible symptoms of coronary artery disease are:
By the time you notice symptoms, secondary problems may have developed. Thus, it is important if you are at risk to have regular check-ups of your heart function.
Is there anything that I can do to stay healthy?
Very much so! The risk for each one of these three heart problems is increased by lifestyle choices. Smoking, lack of exercise, a poor diet, and alcohol (more than an occasional beer or glass of wine) can significantly add to damage done by the radiation. Cocaine is particularly dangerous because it can cause direct damage to the muscle or to the electrical system of the heart. Finally, uncontrolled high blood pressure or diabetes can add to the damage. Bottom line take care of yourself and continue to get regular preventive medical care.
So now that you have scared me with all this information, what should I do?
It is not our intent to scare survivors with these facts and figures, but rather to educate the reader about potential long-term risks related to previous treatment. Many survivors have no heart damage. Many of those who do show damage have no progressive weakening of the heart muscle. However, it is very important to find out about your individual risk. In a past column, we discussed the value of each survivor obtaining a summary of his/her previous cancer treatment, including a list of chemotherapy medications. If you have a list, see if you received any radiation to the chest or heart. If you didnt, this is not a problem you need to worry about. If you did (or if you are not sure), see your doctor and discuss your risk and get any necessary testing.
Nancy Keene is the author of Childhood Leukemia, Childhood Cancer (with co-author Honna Janes-Hodder), Your Child in the Hospital, Working with Your Doctor and Childhood Cancer Surivors (co-authored with Wendy Hobbie RN and Kathy Ruccione). She is Chair of the Patient Advocacy Committee of COG (Children&Mac226;s Oncology Group) and mother of 12-year-old Kathyrn who is a survivor of high risk ALL and 10-year-old daughter Alison.
Dr. Kevin Oeffinger MD directs a multidisciplinary program for young adult survivors of childhood cancer at UT Southwestern at Dallas TX and is partially supported as a Robert Wood Johnson Foundation Generalist Physician Faculty Scholar. He enjoys backpacking, running and hiking with his wife Patty, 16 year old son Daniel and 13 year old daughter Ashley.
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