Starting screening mammograms at age 40 instead of age 50 saves women’s lives, according to a British study.
The research was published online on Aug. 12, 2020, by The Lancet Oncology. Read “Effect of mammographic screening from age 40 years on breast cancer mortality (UK Age trial): final results of a randomised, controlled trial.”
The debate about when to start screening mammograms
A number of 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 and ignited debate over when screening mammograms should start.
Public health experts who question the value of screening 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 and when it should start. 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.
The studies led a number of organizations to revise their breast cancer screening recommendations for women at average risk of breast cancer. The recommendations are all slightly different, so many women aren’t sure when they should start screening mammograms. Here are the current recommendations as of August 2020:
The American Society of Breast Surgeons says:
- All women age 25 and older should have a formal risk assessment for breast cancer.
- Women with an average risk of breast cancer should start annual screening mammograms at age 40.
- Women with a higher-than-average risk of breast cancer should start annual screening mammograms at an earlier age and should be offered additional imaging each year.
The American Cancer Society says:
- Women age 40 to 44 should have the choice to start annual breast cancer screening with mammograms if they wish to do so.
- Women age 45 to 54 should get mammograms every year.
- Women age 55 and older should switch to mammograms every 2 years, or can continue yearly screening.
- Screening should continue as long as a woman is in good health and is expected to live 10 more years or longer.
- All women should be familiar with the known benefits, limitations, and potential harms linked to breast cancer screening.
The U.S. Preventive Services Task Force says:
- Women age 50 to 74 years should have screening mammograms every 2 years.
- The decision to start screening mammography in women younger than age 50 should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin screening every other year between the ages of 40 and 49 years.
Breastcancer.org has always said:
- All women should have a screening mammogram every year, starting at age 40, and continue as long as they are in good health and would want the breast cancer to be treated.
- All women also should have a physical exam of the breasts by a doctor every year and do a breast self-exam every month.
The researchers did this study to provide more information on the benefits of screening mammograms for women age 40 to 48 to help clear up the confusion about when screening mammograms should start.
About the study
In the United Kingdom (UK), screening mammograms are offered by the National Health Service (NHS) every 3 years to women age 50 to 70.
Called the UK Breast Screening Age Trial, this study included more than 160,000 women age 39 to 41 who lived in England, Wales, and Scotland.
The women joined the study between 1990 and 1997. The women were randomly split into two breast cancer screening groups:
- 53,883 women were in the intervention group and had a screening mammogram every year until they turned 49
- 106,953 women were in the control group and had usual care, which meant they had no screening mammograms until they were 50 years old
The women were followed until February 2017.
The researchers wanted to know if starting screening earlier would reduce the number of women who died from breast cancer.
During the follow-up period, 10,439 women died, and 683 of those women (7%) died from breast cancer that was diagnosed before they were 50 years old:
- 209 women in the intervention group died from breast cancer diagnosed before they were 50
- 474 women in the control group died from breast cancer diagnosed before they were 50
This means that about 25% fewer women died from breast cancer in the first 10 years of the study. The researchers noted that this reduction leveled out as all the women started to be screened for breast cancer.
Still, the overall benefit stayed constant until the end of the follow-up period: about one breast cancer death was prevented for every 1,000 women screened.
The results also showed that there was a slight increase in overdiagnosis for women who had annual mammograms from age 39 or 40. The researchers said these overdiagnosed cancers would have been found by NHS mammograms starting at age 50. So starting screening mammograms at age 40 didn’t seem to dramatically increase the number of overdiagnosed cases compared to starting screening at age 50.
“This is a very long-term follow-up of a study which confirms that screening in women under 50 can save lives,” said lead researcher Stephen Duffy, MSc, of the Centre for Cancer Prevention at Queen Mary University of London, in a statement. “The benefit is seen mostly in the first 10 years, but the reduction in mortality persists in the long term at about one life saved per thousand women screened.
“We now screen more thoroughly and with better equipment than in the 1990s when most of the screening in this trial took place, so the benefits may be greater than we've seen in this study,” he added.
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
Not using all three tools in women starting at age 40 is a missed opportunity 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 gene mutations 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 stands by its recommendation that women at average risk of breast cancer have mammograms annually starting at age 40 and 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
Reviewed by: Brian Wojciechowski, M.D., medical adviser
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