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Screening for breast cancer reduces death due to breast cancer in women 50 to 69 years of age who have an average risk

Canelo-Aybar C, Ferreira DS, Ballesteros M, et al. Benefits and harms of breast cancer mammography screening for women at average risk of breast cancer: A systematic review for the European Commission Initiative on Breast Cancer. J Med Screen. 2021 Feb 25:969141321993866.

Review questions

In women who have average risk for cancer, what are the benefits and harms of screening for breast cancer in women less than 50 years, between 50 to 69 years, or between 70 to 74 years of age?

Background

Breast cancer screening involves regular examination of women’s breasts with mammography to detect cancer. Screening is more likely to detect cancer in early stages, when it is small and has had less chance to spread. When detected early, there are more treatment options and often a better outcome. Breast cancer screening may also lead to overdiagnosis, where a cancer that would not have caused harm during a woman’s lifetime is detected and treated, or to false-positive results, where the screening test is positive, but follow-up tests are negative for cancer. False-positive results can cause anxiety and psychological distress due to worry about having breast cancer when breast cancer is not actually present.

How the review was done

The researchers did a systematic review based on studies available up to June 2018.

They found 4 systematic reviews of observational studies and reports from 9 randomized controlled trials.

Key features of the trials were:

  • women had average risk for breast cancer (no personal history of breast cancer, no first-degree relatives [mothers, sisters, or daughters] with a history of breast cancer, no family history of BRCA1 or BRCA2 genes, no history of radiation therapy to the chest to treat lymphoma);
  • women invited to screening were compared with women who did not receive an invitation; and
  • women were followed up for 17 to 24 years.

What the researchers found

Compared with women who did not receive an invitation to screening, screening

  • reduced risk for death from breast cancer in women 50 to 69 years of age and was inconclusive for older or younger women;
  • increased likelihood of overdiagnosis of a cancer that would not have caused harm during the woman’s lifetime;
  • increased psychological distress and risk of invasive procedures (e.g., biopsy) in women with false-positive results on screening (low or very low quality of evidence).

Conclusion

In women with average risk for breast cancer, screening mammography reduces breast cancer–related deaths in those aged 50 to 69 years. In women less than 50 years or more than 70 years of age, the balance of benefits and harms are less clear. Women should discuss the option of screening with their health care provider to determine what is best for them. It is important to note that these recommendations do not apply to women who have a higher-than-average risk for breast cancer.

Invitation vs. no invitation to breast cancer screening in women with average risk for breast cancer

Outcomes

Age groups

Number of studies (number of women)

Effect of screening for breast cancer compared with no screening*

Quality of evidence†

Death due to breast cancer

< 50 years

8 studies (348,478 women)

No difference in effect

Moderate

 

50 to 69 years

6 studies (249,930 women)

An average of 138 to 483 fewer women out of 100,000 would die due to breast cancer (ranging from 60 fewer deaths to 714 fewer deaths)‡

High

 

70 to 74 years

2 studies (18,233 women)

No difference in effect

High

Overdiagnosis§

< 50 years

1 trial (50,430 women)

For every death due to breast cancer that is avoided, about 4 more women will be diagnosed with cancer that would not have caused harm during their lifetime

Moderate

 

50 to 69 years

2 trials (64,117 women)

For every death due to breast cancer that is avoided, about 4 more women will be diagnosed with cancer that would not have caused harm during their lifetime

Moderate

*Ranges depend on the assumed risk for breast cancer before screening.

†Evidence quality was rated using GRADE (Grading of Recommendations Assessment, Development, and Evaluation).

‡Assumed average risk of breast cancer ranges from 0.6% to 2.1%.

§Overdiagnosis is measured as the difference in the cumulative number of breast cancers detected in the invited vs. not invited to screening groups, as a percentage of the cancers diagnosed during the screening phase of the trial in the invited to screening group (individual perspective).




Glossary

False-positive
A test result that suggests the presence of a disease which turns out not to be there.
Observational studies
Studies where the treatment that each person receives is beyond the control of the researcher.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

Related Web Resources

  • Healthy Bones: A Decision Aid for Women After Menopause

    OHRI
    This patient decision aid helps women who have gone through menopause and may have osteoporosis decide on methods to keep your bones healthy. It facilitates the process by outlining and comparing the choices such as medicine, menopausal hormone therapy (MHT), and exercise.
  • Breast cancer: Risks and benefits, age 50-69

    Canadian Task Force on Preventive Health Care
    Your risk of dying from breast cancer is slightly reduced if you have regular screening. However, regular screening increases your chance of a false positive result, a biopsy and having part or all of a breast removed unnecessarily.
  • Breast cancer: Patient algorithm

    Canadian Task Force on Preventive Health Care
    The Canadian Task Force on Preventive Health Care recommends women between 50 and 74 years old who are not at high risk get screened for breast cancer every 2 to 3 years. Talk to your doctor about screening options if you are at high risk or over 74 years old.
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