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Breast Cancers Found by Yearly Mammograms Smaller, Less Advanced Than Cancers Found by Mammograms Every 2 Years

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Women diagnosed with breast cancer after having yearly mammograms were diagnosed with cancers that were smaller and less advanced than women who had mammograms every 2 years, according to results from a small study.

The research was presented on Dec. 4, 2019, at the Radiological Society of North America Annual Meeting. Read the abstract of “Morbidity of Breast Cancer as a Function of Screening Interval: Annual versus Biennial.”

The mammogram debate

Several large studies, including a review by the U.S. Preventive Services Task Force in 2009 and a study on the causes of death in the United Kingdom in 2013, have questioned the value of screening mammograms.

Doctors who question the value of mammograms say that while mammograms do save lives, for each breast cancer death prevented, three to four women are overdiagnosed. Overdiagnosis means either:

  • a screening mammogram finds a suspicious area that would have been eventually diagnosed as cancer by other means, without any effect on prognosis
  • a screening mammogram finds a suspicious area that never would have affected a woman’s health if it hadn’t been found or treated

False-positive results from screening mammograms also have helped fuel the debate about the value of breast cancer screening. When a mammogram shows an abnormal area that looks like a cancer but turns out to be normal, it’s called a false positive. Ultimately the news is good: no breast cancer. But the suspicious area usually requires follow-up with more than one doctor, extra tests, and extra procedures, including a possible biopsy. There are psychological, physical, and economic costs that come with a false positive.

These studies and the resulting stories in the media have fueled an ongoing debate about the value of screening mammograms.

Since that time, the American Medical Association, the American College of Obstetricians and Gynecologists, the American College of Radiology, the National Cancer Institute, and the National Comprehensive Cancer Network all have issued guidelines saying that all women should be eligible for annual screening mammograms starting at age 40. In 2015, the American Cancer Society recommended that annual screening mammograms start at age 45 and then change to having mammograms every 2 years starting at age 55.

Because of all the controversy and confusion, researchers have been studying the benefits and risks of having mammograms every year compared to every 2 years.

“These differing recommendations lead to confusion for both referring physicians and patients,” said Sarah Moorman, M.D., radiology resident at Michigan Medicine, who presented the research.

About the study

The researchers looked at breast imaging records at Michigan Medicine and identified 232 women age 40 to 84 who were diagnosed with breast cancer in 2016 and 2017. All the women were having either annual or every-other-year mammograms:

  • 200 women had annual mammograms, defined as once every 9 to 15 months
  • 32 women had every-other-year mammograms, defined as once every 21 to 27 months

The researchers compared the tumor characteristics and treatment regimens of women who had annual mammograms to those of women who had mammograms every 2 years.

The researchers found that women who had mammograms every year were more likely to be diagnosed with stage I cancer than women who had mammograms every 2 years:

  • 24% of women who had yearly mammograms were diagnosed with stage II, III, or IV breast cancer
  • 44% of women who had mammograms every 2 years were diagnosed with stage II, III, or IV breast cancer

Women who had mammograms every 2 years also were diagnosed with larger cancers. Average tumor size was:

  • 1.4 centimeters for women who had mammograms every year
  • 1.8 centimeters for women who had mammograms every 2 years

Interval cancers, which are cancers found in the time between screenings, were more likely in the women who had mammograms every 2 years:

  • 11% of women who had mammograms every year were diagnosed with interval cancer
  • 38% of women who had mammograms every 2 years were diagnosed with interval cancer

Women who had mammograms every 2 years tended to have more aggressive treatment, such as chemotherapy and axillary lymph node surgery:

  • 12% of women who had annual mammograms compared to 19% of women who had mammograms every 2 years had axillary lymph node surgery
  • 28% of women who had annual mammograms compared to 38% of women who had mammograms every 2 years had chemotherapy

“Our study found that screening mammography performed once a year resulted in less advanced stage disease in patients diagnosed with breast cancer,” said Moorman. “These results may help women make informed decisions about the frequency of breast cancer screening.”

What this means for you

At Breastcancer.org, we believe that a woman’s best chance for early detection requires coordination of our current screening tools:

  • high-quality mammography
  • clinical breast exam
  • breast self-exam

To not use all three tools in women ages 40 to 45 and to do mammograms alone (without clinical or self-exam) in women older than 45 are missed opportunities for early detection.

The reality is that every woman is at risk for breast cancer, and this risk tends to increase over time. It’s important to understand and regularly update your health information related to breast cancer risk throughout your life with your doctor. To get the conversation started, here are some points to talk to your doctor about:

  • family history of breast or other related cancers (ovarian, melanoma)
  • any test results for abnormal genes linked to a high risk of breast cancer
  • results of past breast biopsies, even if they were benign
  • personal history of being treated with radiation to the face and/or chest before age 30
  • breast density
  • weight, if you’re overweight or obese
  • level of physical activity
  • any use of postmenopausal combined hormone replacement therapy (HRT)
  • alcohol consumption, if you regularly drink more than 3 alcoholic beverages per week
  • the amount of processed food and trans fats you eat
  • your smoking history
  • whether or not you had a full-term pregnancy or breastfed

Breastcancer.org recommends that women at average risk of breast cancer have mammograms annually starting at age 40, and it’s very encouraging that this study supports that recommendation. We also believe that monthly breast self-exam and annual physical exams by a doctor are essential parts of an overall breast cancer screening strategy.

If you’re at high risk for breast cancer, you should talk to your doctor about starting annual mammograms at a younger age and consider other screening tools (such as MRI or ultrasound) to maximize the opportunity for early detection.

For more information on the tests and tools used to screen for breast cancer, visit the Breastcancer.org Screening and Testing pages.

Written by: Jamie DePolo, senior editor

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