Does Left Breast Radiation Therapy Increase Your Risk of Heart Disease Compared to Right Breast Radiation? New Study Says Yes, But Context is Important, Experts Say

The study analyzed 972 women who were under the age of 55 when diagnosed with stage I or II invasive breast cancer between 1985 and 2008 with over 60 percent of participants receiving their diagnosis between 1990 and 1999. The median age of diagnosis was 46 and the median length of follow-up was 14 years with a range of one to 29 years. After 27.5 years, 10.5 percent of the women who received left-sided radiation therapy developed coronary artery disease compared to 5.8 percent of women who received right-sided radiation therapy.

But Dr. Chirag Shah, a breast radiation oncologist at Cleveland Clinic, says there’s more to consider beyond the numbers.

“One of the study’s strengths is also its biggest weakness which is its 27.5 year follow up,” Dr. Shah said. “The problem when you look at patients who were treated in 1985 all the way to 2008 is you’re talking about antiquated technology, so it’s kind of like trying to say what's the sound quality with the newest iPod when looking at data from a Walkman."

The Debates Around Radiation for Breast Cancer

Dr. Shah went on to explain that doctors used two dimensional radiation in 1985, but they’ve come a long way since.

“To put it in comparison, in 1985 we didn’t really even use CAT scans in radiation planning… and that subsequently evolved into the ’90s where we started using CAT scans and three-dimensional imaging to where we are now which is we have multiple techniques to not only calculate the dose to the heart, but to also way reduce dose to the heart."

Dr. Chelsea Pinnix, the associate residency program director in the department of radiation oncology at MD Anderson Cancer Center, has previously talked to SurvivorNet about how radiation therapy works and how it’s evolved over time.

“In general, the radiation actually provides DNA damage and that damages the cell and leads to cell death,” Dr. Pinnix said. “There is a consideration in terms of having the ideal toxicity/benefit ratio, and so ultimately we want to be as focused as we can with our radiation targeting in minimizing side effects. And the way to do that is to minimize the radiation dose to surrounding normal structures.”

Things like body positioning and breath holding can help with minimizing dosage, but today’s technology can help “avoid the areas that are unnecessary to be included in the radiation field.”

Because these techniques weren’t available for the first part of the study, Dr. Shah says the results are of limited utility. According to Dr. Shah, the overall average estimated mean dose of radiation to the heart for women with left-breast cancer was recorded as 6.6 units in 2013. But with modern techniques today, the average is 1.4 units of radiation for left-sided breast cancer without lymph node involvement and 2 units of radiation for left-sided breast cancer with lymph node involvement. And while risk of heart disease is important to think about, Dr. Shah said there’s good data showing that radiation therapy is safe and effective.

“I would say that it's important for them to be aware of it, but I think that the most important take away is that if you have a left-sided breast cancer, to make sure you talk to your radiation oncologist about what techniques they're using to protect your heart,” he said.

Understanding Breast Cancer

Screening for breast cancer is typically done via mammogram, which looks for lumps in the breast tissue and signs of cancer. And while mammograms aren't perfect, they are still a great way to begin annual screening. The American Cancer Society (ACS) recommends women begin mammogram screening for breast cancer at age 45. It's also important to be on top of self breast exams. If you ever feel a lump in your breast, it's important to be vigilant and speak with your doctor. Voicing your concerns as soon as you have them can lead to earlier cancer detection which, in turn, can lead to better outcomes.

RELATED: When Should I Get a Mammogram?

There are many treatment options for people with this disease, but treatment depends greatly on the specifics of each case. Identifying these specifics means looking into whether the cancerous cells have certain receptors. These receptors   the estrogen receptor, the progesterone receptor and the HER2 receptor  can help identify the unique features of the cancer and help personalize treatment.

RELATED: Treatment for HER2-Positive Breast Cancer

"These receptors, I like to imagine them like little hands on the outside of the cell, they can grab hold of what we call ligands, and these ligands are essentially the hormones that may be circulating in the bloodstream that can then be pulled into this cancer cell and used as a fertilizer, as growth support for the cells," Dr. Elizabeth Comen, a medical oncologist at Memorial Sloan Kettering Cancer Center, tells SurvivorNet.

The Unique Features of Breast Cancer: Deciding the Right Course of Treatment

One example of a type of ligand that can stimulate a cancer cell is the hormone estrogen, hence why an estrogen receptor positive breast cancer will grow when stimulated by estrogen. For these cases, your doctor may offer treatment that specifically targets the estrogen receptor. But for HER2 positive breast cancers, therapies that uniquely target the HER2 receptor may be the most beneficial.

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