TUESDAY, Dec. 27 (HealthDay News) — Women who have breast cancer
on the left side of the body and who are treated with radiation therapy
have a higher risk of developing narrowing of the arteries that lead to
the heart, researchers say.
A new Swedish study found that the risk of having moderately narrowed
coronary arteries was more than four times greater for women who had
left-sided breast cancers treated with radiation compared to right-sided
breast cancers treated with radiation. The odds were seven times higher
for more severe narrowing on the left side versus the right, according to
the study published in the Dec. 27 online edition of the Journal of
Clinical Oncology.
“We suggest that the coronary arteries be regarded as organs at risk in
radiation therapy, and that every effort be made to avoid radiation dose
to the coronary arteries,” wrote study authors led by Dr. Greger Nilsson,
of the department of oncology, radiology and clinical immunology at
Uppsala University Hospital.
However, it’s also important to note that of a group of 8,190 women who
had breast cancer, just 199 had to be referred for coronary angiography (a
treatment for blocked blood vessels).
“Women need to be aware that there is a risk, but the overall risk is
still relatively small, and the benefits of radiation in the treatment of
breast cancer still outweigh the risks,” said Dr. Stephanie Bernik, chief
of surgical oncology at Lenox Hill Hospital in New York City.
Cancer treatments, such as radiation and chemotherapy, are designed to
destroy cancer cells. Unfortunately, healthy cells are often damaged, too.
Treatment techniques are constantly being refined, and today’s treatments
target fewer healthy cells than treatments from years past.
For example, newer radiation techniques help protect the heart and the
arteries leading to it, according to Dr. Timothy Zagar, an assistant
professor in radiation oncology at the University of North Carolina at
Chapel Hill. One such technique is to give bursts of radiation only when a
patient is taking a deep breath. During a deep breath, the main artery
going to the heart separates from the breast and chest wall, which keeps
it away from the radiation.
Zagar, co-author of an accompanying editorial in the same issue of the
journal, said researchers don’t know exactly how radiation causes damage
to coronary arteries, but it’s believed to damage the cells lining the
arteries (endothelial cells), which causes inflammation, which can lead to
hardening of the arteries.
The current study included women from Sweden who were diagnosed with
breast cancer between 1970 and 2003. Of the 8,190 women, the researchers
found 199 women who had undergone coronary angiography, suggesting
significant coronary artery disease.
Coronary artery narrowing (stenosis) is graded on a scale of zero to 5.
Zero indicates a healthy blood vessel, while 5 indicates a blocked blood
vessel.
When the researchers compared women who’d had radiation treatment on
the left side of their body versus the right, they found that the odds of
a grade 3 to grade 5 stenosis in a left-sided artery were 4.38 times
higher. The odds of a grade 4 or grade 5 stenosis were 7.22 times higher
for women who had left-sided breast cancer.
In women who received radiation in high-risk areas near the heart’s
arteries, the risk of a grade 3 to grade 5 stenosis was nearly twice as
high as it was in women who had radiation in low-risk areas, or who didn’t
have radiation.
Zagar pointed out that this study was done over a long period of time
and that changes in the way radiation is delivered would likely result in
lower odds of coronary artery stenosis for women treated with radiation
today.
In addition, Zagar said, “I don’t think this study’s findings would
justify changing from a lumpectomy [breast-conserving surgery] to a
mastectomy [surgical removal of the breast]. Breast-conserving therapy is
very important to many women, and the number of coronary events are still
low,” he added.
“It’s important to understand that with all treatments, there are
risks,” Bernik said. “And, we know that this is one of the risks with
radiation of left-sided breast cancer. Women need to keep in mind that
they’re at increased risk of coronary events and need to follow up with
their doctor going forward.”
More information
Learn more about radiation treatment for cancer from the U.S. National Cancer Institute.
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