Risk of Heart and Lung Problems From Breast Radiation Higher for Smokers

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For women diagnosed with early-stage breast cancer, lumpectomy followed by radiation therapy has been shown to be as effective as mastectomy without radiation for removing the cancer AND minimizing the risk of the cancer coming back (recurrence). Radiation therapy after lumpectomy can destroy any cancer cells that may have been left behind after surgery, making recurrence less likely.

Still, studies have found a link between radiation therapy for breast cancer and a higher risk of heart and lung problems, especially if the cancer is in the left breast, the same side as the heart. Radiation therapy uses a special kind of high-energy beam to damage cancer cells. Over time, radiation damages cells that are in the path of its beam -- normal cells as well as cancer cells. But cancer cells are more affected by radiation than normal cells because they’re less organized.

A study looking at results from a number of other studies found that smokers have a much higher risk of dying from lung cancer or a heart attack as a result of radiation therapy for breast cancer.

The study was published online on March 20, 2017 by the Journal of Clinical Oncology. Read “Estimating the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomized Trials.”

This study is a meta-analysis -- a study that combines and analyzes the results of many earlier studies. In this case, the results of 40,781 women in 75 studies published between 2010 and 2015 were analyzed. All the women had been diagnosed with either early-stage breast cancer or DCIS (ductal carcinoma in situ) and then were randomly assigned to either be treated with surgery and radiation or surgery alone. The 75 studies included 647 radiation regimens. The women were followed for about 10 years. Few of the women were treated with hormonal therapy or chemotherapy:

  • 23% were treated with tamoxifen
  • 19% were treated with chemotherapy

The researchers wanted to estimate the risks of modern breast cancer radiation therapy.

Radiation therapy after breast cancer surgery is usually given as one treatment per day, 5 days a week for 5 to 7 weeks. A Gray is the way radiation oncologists measure the dose of radiation therapy; if you’re on a 5-week treatment schedule, 50 Gray is the usual amount given during the 5 weeks (2 Gray at each treatment). A supplemental “boost” dose may be included at the end of the regimen that targets the area where the cancer was. Some newer radiation regimens involve fewer treatments with higher doses of radiation given at each treatment, but less total radiation. These new schedules are called “low dose” or “accelerated hypofractionated” radiation.

Because modern breast cancer radiation therapy techniques have improved and are better at avoiding the lungs and heart than the techniques used in the studies in the meta-analysis, the researchers also reviewed recent studies to take into account how radiation therapy for breast cancer is better targeted now.

The researchers determined the average radiation doses that the women’s hearts and lungs received:

  • 5.7 Gray for the whole lung (the lung on the same side as the cancer received an average of 9.0 Gray and the lung on the opposite side of the cancer received an average of 2.4 Gray)
  • 4.4 Gray for the whole heart (when the breast cancer was on the left side, the heart received an average of 5.2 Gray and when the breast cancer was on the right side, the heart received an average of 3.7 Gray)

The researchers noted that some treatment centers were able to avoid exposing the heart to that much radiation and had an average whole heart radiation dose of less than 2 Gray, even when the breast cancer was on the left side.

During follow-up, 20,345 of the women died; 6,064 of these women had no breast cancer recurrence.

Compared to women who didn’t have radiation therapy, women who were treated with radiation therapy were more likely to be diagnosed with lung cancer, leukemia, esophageal cancer, and heart disease.

The researchers then looked at the risks of radiation therapy in women who were long-term smokers compared to women who didn’t smoke. The estimated risk of dying from lung cancer from modern breast cancer radiation therapy was:

  • 4% for long-term smokers
  • 0.3% for non-smokers

The estimated risk of dying from heart problems from modern breast cancer radiation therapy was:

  • 1% for long-term smokers
  • 0.3% for non-smokers

The researchers pointed out that the risks of modern radiation therapy for breast cancer may outweigh the benefits for long-term smokers. Still, for most non-smokers and former smokers, the benefits of radiation therapy outweigh the risks.

"For non-smokers, the absolute risk of death from the side effects of modern radiotherapy is only about 0.5%, which is much less than the benefit. But for smokers, the risk is about 5%, which is comparable with the benefit,” said Carolyn Taylor, M.D., radiation oncologist at the University of Oxford and lead author of the study. "Stopping smoking at the time of radiotherapy will avoid most of the lung cancer and heart disease risk from radiotherapy, and has many other benefits."

Advances in radiation therapy have greatly reduced the amount of radiation exposure to the heart, lungs, and other healthy tissue. Doctors use computers to plan radiation therapy that is extremely precise in dose and delivery. Some radiation therapy equipment (called respiratory gating) tracks heartbeats and lung movement and effectively blocks those tissues from radiation exposure. Other tools, such as intensity modulated radiation therapy, allow the oncologist to change the intensity of the radiation during treatment to avoid healthy tissue.

Still, as this study strongly suggests, it makes sense to quit smoking if you’ve been diagnosed with breast cancer. Besides increasing the risks of radiation therapy, smoking also can make it harder for you to heal after surgery and can increase your risk for blood clots if you’re taking hormonal therapy medicine.

If you don't smoke, don't start. If you do smoke, use every resource you can find to help you quit. Knowing about all of the problems associated with smoking isn't always enough to make you quit. Smoking is a habit that's very hard to break. Fortunately, if you're serious about trying, you have lots of help:

  • The American Lung Association offers a free online smoking cessation program. The American Cancer Society also has a quit smoking program. You can also call the American Cancer Society at 1-800-ACS-2345 to get support and free advice on how to stop smoking from trained counselors.
  • Medicines to help you quit can be taken as a pill, chewed as gum, or worn as a patch on the skin. Ask your doctor if one of these might be right for you.
  • Acupuncture and meditation may help ease cigarette cravings.
  • It's also easier if you have a friend who's also quitting or who can cheer you on when you're feeling you can't make it on your own.
  • The Breastcancer.org Discussion Boards has the Stop Smoking Support Thread, where you can meet others to give and receive support to quit smoking.

If you’ve been diagnosed with early-stage breast cancer, you and your doctor will consider the characteristics of the cancer, your unique situation, your personal preferences, your surgical options, and your treatment options after surgery when creating your treatment plan. If you choose lumpectomy, it’s very likely that radiation will be recommended after surgery. Talk to your radiation therapy treatment team about how they’ll make sure that you get only the radiation therapy required to effectively treat the cancer. Together, you can plan your treatment to minimize any risks.

You can learn more about radiation after breast cancer surgery in the Breastcancer.org Radiation Therapy section.


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