Liz Szabo, USA TODAY
Women treated with radiation for breast cancer face an increased risk of heart attacks and death, even 20 years after the end of treatment, a new study shows.
The study is the latest to document the serious long-term health problems faced by cancer survivors. Although improved treatments allow more people today to survive their disease, these toxic therapies also lead many to suffer chronic health problems.
Radiation, for example, is a key component of breast cancer therapy and significantly reduces the risk that tumors will return. But beams of radiation can penetrate beyond the breast to the heart and the arteries that feed it, according to a study published online Wednesday in the New England Journal of Medicine.
In a study of 2,168 breast cancer patients who had radiation therapy between 1958 and 2001 in Sweden and Denmark, doctors found that any amount of radiation increased the risk of heart disease. Researchers defined heart disease to include heart attacks, surgeries such as a bypass or angioplasty, or a heart-related death.
Read copy of full study here
"This is a major concern," says Ben Smith, an assistant professor of radiation oncology at M.D. Anderson Cancer Center in Houston, who was not involved in the new study. In spite of improvements in technology, Smith says many women around the country "still have a significant portion of their heart in the path of the radiation beam."
More than 232,000 American women will be diagnosed with breast cancer this year, according to the American Cancer Society. About 3 million American women today are survivors.
Women who received radiation to the left breast, which is slightly closer to the heart, were at especially high risk, the study says. Women with pre-existing heart disease also had a higher risk. Heart problems were generally most common in the first five to 10 years after treatment.
Over the course of 20 years, the risk of heart disease increased an average of 7.4% with each additional unit of radiation, called a gray. Women in the study received an average radiation dose of 4.9 gray to the heart, although some women received up to 27 gray.
Doctors have worked to reduce unnecessary radiation exposure over the years, experts note.
But American women being treated today may still receive radiation of about 2 to 5 gray to the heart, Smith says. New technology allows doctors at his hospital to reduce that exposure even further, to a fraction of 1 gray.
Yet the risks described in the new paper "may represent just the tip of the iceberg," wrote Javid Moslehi, a cardiologist specializing in the care of cancer patients at Boston's Dana-Farber Cancer Institute.
That's because radiation can cause not just narrowing of the arteries and heart attacks, but abnormal heart rhythms, malfunctioning heart valves and other serious issues, which weren't measured in this study, Moslehi writes.
Certain chemotherapy drugs also can cause heart failure, he writes. In the new study, only eight patients got chemo.
Lastly, chemo often throws women into early menopause, which causes many breast cancer survivors to gain weight, says Jody Schoger, a breast cancer survivor and advocate from The Woodlands, Texas. That puts further stress on the heart.
Because cancer treatment can damage the heart and blood vessels in so many ways, leading a healthy lifestyle - with a good diet, lots of exercise and no smoking - is critically important, Smith says.
Cardiologists and family doctors also can help women manage their risks, says cardiologist Christopher Cannon, a professor at Harvard Medical School. Breast cancer survivors could be screened early, for example. Doctors have a wide variety of medications, from aspirin to statins, that also can reduce women's risks, he says.
Eric Winer, director of breast medical oncology at Dana-Farber, says patients should not avoid potentially lifesaving radiation therapy because of the risk of heart disease.
"Radiation is remarkably safe and well-tolerated," Winer says. "It would be a mistake to conclude from this that we should use radiation less often."
But doctors agree that scientists should continue to look for ways to reduce women's risks.
At M.D. Anderson, women can now receive radiation therapy that is synchronized with their breath, Smith says. Inhaling deeply pushes the heart down, and out of the radiation beam. New technology starts and stops the radiation beam automatically as women breathe in and out, nearly eliminating exposure to the heart, he says.
Radiation's risks to the heart loom especially large when women have very early cancers that may not prove life-threatening, Smith says. About 60,000 women a year are diagnosed with a condition called DCIS, or ductal carcinoma in situe. Experts disagree on whether these "Stage O" tumors represent very early cancers or pre-cancers.
About 30% to 40% of DCIS progresses into invasive cancer, although not all of those tumors are life-threatening, Winer says.
Because of that uncertainly, women with DCIS are typically treated as if they have an early cancer, with a lumpectomy, radiation and sometimes hormone therapy.
While radiation reduces the risk that women will be diagnosed with a new case of DCIS or cancer, there's no evidence to show it improves survival, Winer says.
"Any concerns about radiation become an even bigger issue for women who have very early stage breast cancers like DCIS, where women have to very carefully weight the pros and cons of treatments," Winer says. "We need to figure out which women with DCIS need treatment to spare women from the side effects."
Smith encourages breast cancer patients to talk to their doctors about taking steps to reduce their risks.
"Some practices do amazing work to essentially spare the heart," says Smith, who serves as a consultant to review radiation plans from doctors around the country. "And there are others that pretend the heart isn't even there. This is a teachable moment for doctors."