Big Blow To Radiation Therapy For Breast Cancer - Part I
Radiation is widely used as a follow-up (adjuvant) treatment after surgery for breast cancer. It is primarily administered to prevent recurrences and is quite effective at doing so. But a study published in the March 7th Journal of the National Cancer Institute has shown that radiation also increases the risk of heart disease in women who receive it following surgery for breast cancer. Using modern radiation delivery techniques shifts the pattern of harm, but does not remove it.
It has long been acknowledged that the type of radiation used in the 1960s and 1970s elevated women’s risk of subsequent cardiovascular disease. But techniques have changed since then, and radiation oncologists have often stated that newer radiation delivery procedures have been deliberately designed to minimize this sort of heart damage. The dangers of radiation to the heart have therefore frequently been dismissed as a thing of the past, and countless women have been told that the procedures performed on them were safe.
For example, in “Clinical Oncology,” a textbook published in 2001 by the American Cancer Society, the problem is downplayed. In the course of two paragraphs, its seriousness is minimized half a dozen times!
“Cardiac toxicity due to irradiation is rare…Effects on the endocardium are rare…Below a total dose of 4500 cGy, radiation-induced damage is uncommon…Tamponade [a life-threatening compression of the heart resulting from a collection of fluid in the pericardium (the sac surrounding the heart), ed.] occurs infrequently. In general, pericarditis is self-limited… Chronic pericarditis is uncommon. Acute myocardial infarction [is] rare…” (Lenhard 2001: 243-244).
Many Web sites similarly claim that modern radiation therapy is entirely safe. Here is an example of such a statement from breastcancer.org:
“Radiation therapy techniques have changed dramatically since then [the 1970s, ed.]. New technology allows doctors to use the lowest dose of radiation possible. They can also more precisely target the radiation to the breast and away from the heart - so the heart receives a minimal amount or none at all.”
This is what the medical profession believed, and wanted us to believe. However, the facts now speak otherwise. The JNCI study is unquestionably a major blow to the profession’s insistent claims that radiation has evolved into a safe modality for the post-operative treatment of breast cancer.
In the JNCI study, researchers at the Netherlands Cancer Institute in Amsterdam evaluated 4,414 breast cancer patients who survived for at least 10 years after receiving radiotherapy between the years 1970 and 1986. The patients were followed for a median of 18 years. These patients’ rates of cardiovascular disease were then compared with those seen in the general population (Hooning 2007). In other words, this was a very large and prolonged study.
There were a total of 942 “cardiovascular events” during the follow-up period. The good news was that radiation therapy limited to the breast itself did not increase the risk of cardiovascular disease. However, when either the left or right internal mammary chain of lymph nodes was included in the radiation field, as is common in post-operative radiotherapy, it did significantly increase that risk.
Internal mammary chain irradiation performed during the 1970s increased the risk of a heart attack (myocardial infarction) by 2.55 times compared to no radiation. It also raised the risk of congestive heart failure 1.72-fold. Radiotherapy given in the 1980s was also associated with an increased risk of heart disease: a 2.66-fold greater risk of heart failure and a 3.17-fold greater risk of dysfunctional heart valves. (This was one of the first studies to investigate radiation-related heart valve failure.)
In the 1980s, it became common to add adjuvant chemotherapy to radiotherapy. The standard chemotherapy regimen used during the 1980s was CMF (which stands for the three drug combination of cyclophosphamide, methotrexate and 5-fluorouracil). However, this study found that the addition of CMF chemotherapy to radiation conferred a 1.85-fold increased risk of congestive heart failure. This finding has caused a great deal of surprise since this combination was never thought to be particularly cardiotoxic.
It is chilling to realize that nowadays CMF chemotherapy has been replaced by regimens based around so-called anthracycline drugs, the most prominent of which is Adriamycin (doxorubicin). This class of drugs is already well known to carry serious risks of cardiotoxicity, including life-threatening congestive heart failure. This risk increases exponentially the greater the lifetime dose.
A recent review in Seminars of Oncology concluded that “10 percent to 26 percent of patients administered cumulative anthracycline doses above those recommended…develop congestive heart failure, and that more than 50 percent of patients administered these doses will experience measurable functional impairment months to years after the end of therapy.” Also, the susceptibility of patients to anthracycline-induced cardiotoxicity varies widely, with a dramatic increase with advancing age (Jensen 2006).
The risk is further augmented by the addition of Herceptin (trastuzumab), another cardiotoxic drug that is increasingly used in the treatment of breast cancer. Herceptin can cause heart damage ranging from mild and transient to life-threatening congestive heart failure. To quote the package insert warning, mandated by the Food and Drug Administration, Herceptin “has been associated with disabling cardiac failure, death, and mural thrombosis leading to stroke” (FDA 2003). (Mural thrombosis is the formation of a fibrinous clot on the endocardial lining of the heart, or on the wall of a large blood vessel).
In view of these ominous warnings, studies focusing on the cumulative cardiac risk of radiation therapy in patients who have also been given Adriamycin and/or Herceptin-containing chemotherapy regimens are urgently needed.
The JNCI study also found a disturbing three-fold increase in the risk of heart attacks among radiotherapy-treated patients who also smoked tobacco. The authors properly caution that “irradiated breast cancer patients should be advised to refrain from smoking to reduce their risk for cardiovascular disease.” Easier said than done! The more logical solution would surely be to refrain from giving adjuvant radiation to patients who insist on smoking.
