Following my initial article in the Summer edition of Buddies For Life I would like to focus my attention in this article on the different forms of therapy that are used for the treatment of breast cancer and how they can impact on the heart.
Both chemotherapy (drug treatment) and radiotherapy can affect the heart, but early detection methods, and effective treatments, are available.
Anthracyclines (Adriamycin / Doxorubicin)
This group of drugs has been used for many years in the treatment of breast cancer. I must emphasize that abnormalities of the heart due to these drugs are quite rare as oncologists now use a carefully measured dose based on the patient’s body weight, causing the incidence of heart disease to drastically reduce.
The way these drugs cause cell death is complex but is related to damage to the internal functioning mechanisms of cells – both cancer cells and heart cells. The drug damages the heart muscle and can cause the heart to function abnormally and ultimately cause heart failure.
Although Anthracyclines may cause heart abnormalities, the presentation of heart failure will sometimes only occur many years later, even 20 to 30 years later, as the heart has compensating mechanisms that allow it to function normally even though it has been damaged.
This drug has had a dramatic impact on the survival of breast cancer patients who have an over expression of the HER-2 receptor (human epidermal growth factor -2) in their cancer cells.
Herceptin can also affect the heart, cause abnormalities in heart function and, ultimately, heart failure. Whereas Anthracycline damage is permanent, Herceptin appears to cause reversible damage to the heart muscle and does not permanently kill the muscle cells of the heart – but rather causes the cells to work abnormally. Most patients who develop problems with the heart on Herceptin have previously been on Anthracyclines.
When heart function abnormalities are detected the Herceptin can be temporarily stopped and treatment for the heart condition initiated. The heart function will almost always return to normal.
Information on the effects of radiotherapy on the heart comes from studying the effects of radiation on atom bomb survivors of the 2nd World War and the impact of radiation on childhood cancer survivors.
Many patients with breast cancer receive radiotherapy as part of their treatment. Radiotherapy can cause damage to the heart that may also only manifest many years after cancer treatment has ceased. Modern treatment involves lower doses of radiotherapy and much better protection of the heart thus resulting in less risk of developing heart problems later in life.
The most common problems are with the pericardium (the lining of the heart). It presents as a sudden onset of chest pain due to pericarditis (inflammation of the pericardium). This is reversible and responds well to analgesics and anti-inflammatory drugs. Cortisone is sometimes also prescribed.
Many years after radiation therapy a narrowing or obstruction of the blood vessels supplying the heart muscle (coronary arteries) may occur which can cause a heart attack. Damage to the valves of the heart has also been described.
In conclusion, a lot has been learnt over the years about the effects of chemotherapy and radiotherapy on the heart. Because of this knowledge much has been done to prevent, detect and reverse or treat these heart problems.
Written by Dr Len Steingo