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Radiation Fallout - Today's radiation therapy is safe for the heart, but breast cancer patients treated prior to 2000 may still be at risk.

By Delthia Ricks

Does radiation therapy cause cardiovascular disease? This worry has dogged breast cancer patients for years, and with good reason: until approximately the year 2000, old and imprecise radiation technology often damaged hearts. Since then, there's been a technology revolution, with new equipment and techniques so vastly improved that healthy tissue is generally left unscathed. The risk of heart damage is now small, say radiation oncologists, but we need to get the word out. Despite greater safety, anxiety remains high, causing the lifesaving treatment to be underused. (Four out of 10 women treated for breast cancer in the United States currently receive radiation therapy; for those who undergo treatment following a lumpectomy, radiotherapy reduces by nearly 70 percent the chance that cancer will recur in the same breast.)

A Legacy of Risk

The concern about long-term cardiac disease following radiation therapy comes from studies of women who were treated decades ago, during the 1960s, 1970s and 1980s, says radiation oncologist Paul Gliedman, M.D., of Continuum Cancer Centers of New York. "Back then, the technology was different, and our understanding of what we needed to treat was also different."
Years ago, doctors treated a larger portion of the chest because radiation beams could not be controlled as well as they are today (thanks to computer-aided technology). Some radiation oncologists were probably more concerned about defeating cancer and less worried about preventing side effects—even those caused by grazing the heart.
Patients treated from the 1960s through the early 1980s may be at especially high risk of heart disease. Studies eventually found that patients who received old-style radiotherapy were significantly more likely to develop coronary artery disease that led to heart attacks and fatal cardiac arrest.

Left Breast Danger

When it comes to radiotherapy, it turns out, what's done is not done. Women who underwent the treatment during and before the 1990s got a wake-up call last summer, when researchers at the University of Pennsylvania discovered that some of them—those treated on the left side of the chest—were particularly vulnerable to radiation-induced heart disease. Doctors attribute the finding to a simple matter of physiology: the heart is situated in the center of the chest cavity, but approximately two-thirds of the fist-size organ lies toward the left.

The finding, based on analysis of women treated for breast cancer between 1977 and 1994 and published in the Journal of Clinical Oncology last August, is highly relevant to public health. Hundreds of thousands of women successfully treated for breast cancer with old-style radiotherapy may have developed heart conditions, yet not realized there was a link to the radiation therapy received in the past. For those treated in the 1990s, cardiovascular disease may have yet to manifest.
When the risk factor of old-style radiotherapy is added to other risks, from smoking to obesity to family history of breast cancer, some patients may be more vulnerable to heart trouble than they think."The truth is, many patients still alive today were treated after we saw the need for cardiac protection but before we enhanced the technology," says study leader Eleanor Harris, M.D.

State of the Art

What a difference a decade has made. Today patients go to simulation sessions—dry runs—of the actual treatment at least three weeks before radiotherapy begins. Radiation oncologists at major centers are aided by medical physicists and other scientists to customize each patient's treatment. State-of-the-art equipment provides a three-dimensional view of the area to be treated. The amount of radiation to be delivered is precisely calculated. "There is no guesswork," Gliedman says.
Technology has been so vastly improved that the heart is left virtually unscathed "Some major things have happened in breast cancer treatment," adds Gliedman. "There is a much better understanding of the disease itself, and the technology has improved to keep up." For instance, radiation dosages are "fractionated"—meted out—in small, far safer amounts delivered daily, five days a week, during a six- to seven-week treatment regimen. Gliedman marvels as well at the use of intensity-modulated therapy—a technique that allows the radiation oncology team to deliver a keenly targeted dose. He also cites emerging techniques. One such method is called MammoSite, a radiation therapy system that delivers a full course of radiation through an internally placed catheter in a five-day treatment regimen. Marisa Weiss, M.D., director of breast radiation oncology at Lankenau Hospital in Philadelphia, says that current technology takes into account the complexity of the cardiovascular system. "Modern technology allows for the beating of the heart and the movement of the heart with respiration," Weiss says. The position of the heart varies with each breath and with each lub-dub, lub-dub—the syncopated beat of life. Having all of this information in hand helps the radiation oncology team develop an optimum treatment plan, one that shields the heart. "With that dynamic information, you can modify the beam where you need to," Weiss says. "I use special features of a modern linear accelerator together with complex treatment planning to modulate radiation dose based on each woman's unique dynamic anatomy." For example, technology now allows doctors to "bend" a beam of radiation as it flows from a linear accelerator to bypass vital structures within the body, the heart included. A beam can even be "refined" to minimize skin irritation. "Newer techniques can usually allow the radiation oncologist to block the heart out completely," Weiss states. Over the past several years, radiation oncologists specializing in breast cancer have garnered an impressive track record when it comes to protecting patients' hearts. But it's still important for patients to stay aware. While today's radiation technology is vastly safer than systems of the past, it's too new to have been studied over the long term. So while the risk appears smaller, it's impossible to know whether we're totally out of the woods when it comes to protecting the heart. Gliedman and Harris underline the necessity of continuing scientific inquiry into cardiovascular problems caused by radiation therapy to the chest.

Questions for your Radiation Oncologist

With so many emerging choices, patients should be at the helm of their own care, posing questions to physicians long before radiation therapy begins. What equipment is used, and what is its track record in terms of protecting the heart? Are there better options? For questions to start with, look below:

Where did you train?
Radiation oncologists educated at major cancer centers or research hospitals are best.

Do you specialize in breast cancer?
If the answer is no, find someone else.

Do you plan radiation treatment using CT or MRI technology?
The answer should be yes. This kind of advance planning provides a 3-D image of your body's organs, so that during therapy the radiation beam is directed only to the location of the tumor, and not your heart.

Do you have 3-D conformal radiation?
You want this technique. It produces a radiation beam that targets specific parts of your body, allowing normal tissue to be blocked out of the radiation field. It is available at most treatment centers.

Do you have intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT)?
In the best of all possible worlds, your radiation oncologist would avail herself of these growing techniques, but she can do an acceptable job without them. IMRT is a technique that may be able to better target the dose of radiation to the breast area, while avoiding dose to the normal surrounding tissues. IGRT is an even more controlled technique that adjusts the radiation beam in real time. Only some treatment centers have IMRT and IGRT, since they're still relatively new.