Breast cancer screening: benefits and disadvantages

Screening is offered because it can find breast cancer early. It also has costs, and the honest picture includes both. This page sets out the benefits and the main disadvantages: false alarms, extra tests, overdiagnosis, false reassurance, anxiety and radiation. Every figure is attributed to its source and population, because estimates differ between studies and countries. Whether to take part is a personal choice, and your own doctor or screening service can help you weigh it.

What screening can do

The NHS in England says it offers screening because it can save lives, by finding cancers too small to feel or see, when treatment may be simpler and more likely to work.11NHS England: Your guide to NHS breast screening Crown copyright 2026; explains why the NHS offers screening and its main risks. The US Preventive Services Task Force concluded with moderate certainty that screening every 2 years at ages 40 to 74 has a moderate net benefit.22US Preventive Services Task Force: Breast Cancer Screening Published April 30, 2024; moderate net benefit for 40 to 74. Its modeling estimated 8.2 breast cancer deaths averted per 1,000 women screened over a lifetime, though that is a model, not a measurement.22US Preventive Services Task Force: Breast Cancer Screening Table 2 modeling: median 8.2 deaths averted per 1,000 women for biennial screening at 40 to 74.

Not every review is as favorable. A 2013 Cochrane review of seven trials found that the most reliable trials did not show a statistically significant reduction in breast cancer deaths, and noted that treatment has improved since the trials were run.33Cochrane: Screening for breast cancer with mammography Published 4 June 2013; summary of seven trials with about 600,000 women aged 39 to 74. An independent UK panel in 2012 concluded that screening reduces breast cancer deaths but that some overdiagnosis occurs.44The Lancet: The benefits and harms of breast cancer screening, an independent review Published 17 November 2012; 20% relative reduction in breast cancer mortality for women invited to screening.

False positives, recall and extra tests

A false positive is an abnormal result when no cancer is present. A recall (or callback) is an invitation back for more tests after screening. In England, for every 100 people screened, 96 need no further tests and 4 do; of those 4, 1 is diagnosed with breast cancer. These figures are a guide for the general population.11NHS England: Your guide to NHS breast screening Crown copyright 2026; 96 in 100 need no further tests, 4 do, and 1 of those 4 has cancer. The American Cancer Society says fewer than 1 in 10 women called back are found to have cancer.55American Cancer Society: Getting Called Back After a Mammogram Last revised July 23, 2026; a callback does not mean cancer.

Over many years the chances add up. USPSTF modeling estimated 1,376 false-positive results per 1,000 women screened every 2 years from 40 to 74 over a lifetime (results, not women).22US Preventive Services Task Force: Breast Cancer Screening Table 2 modeling for a lifetime of biennial screening at 40 to 74. The American Cancer Society says about half of women having yearly mammograms for 10 years will have a false-positive finding at some point.66American Cancer Society: Limitations of Mammograms Last revised July 23, 2026; false-positive rates by age, density and screening history. Follow-up can include more mammograms, ultrasound or a biopsy. For how results are labeled, see BI-RADS categories explained.

Overdiagnosis

Overdiagnosis means finding a breast cancer that would never have become a threat to a person's health, or even apparent, during their lifetime. No one can tell which individual cancers these are, so estimates come from comparing whole groups.22US Preventive Services Task Force: Breast Cancer Screening Defines overdiagnosis and explains why it cannot be observed in one person. Because doctors cannot yet tell, almost everyone diagnosed is treated.77Cancer Research UK: Breast screening (mammography) Last reviewed 21 May 2026; says doctors cannot yet tell which cancers need treatment.

The estimates vary. The independent UK panel's approximate guide was that, for every 10,000 UK women aged 50 invited to screening for 20 years, 43 breast cancer deaths would be prevented and 129 cases overdiagnosed, with substantial uncertainty.44The Lancet: The benefits and harms of breast cancer screening, an independent review Figures are described by the panel as an approximate guide with substantial uncertainty. Cochrane assumed a higher overdiagnosis rate of 30%, giving 10 healthy women treated unnecessarily for every 2,000 invited over 10 years, against one death avoided.33Cochrane: Screening for breast cancer with mammography Authors assume 15% fewer breast cancer deaths and 30% overdiagnosis, and say the absolute effect today is likely smaller. The USPSTF modeling gave 14 overdiagnosed cases per 1,000 women over a lifetime of screening at 40 to 74, with a range of 4 to 37 across models.22US Preventive Services Task Force: Breast Cancer Screening Table 2 and text: 14 overdiagnosed cases per 1,000 women, range 4 to 37 across models. Those numbers describe different populations and methods, so they should not be compared directly.

False reassurance and interval cancers

Screening misses some cancers. The American Cancer Society says screening mammograms miss about 1 in 8 breast cancers, more often in dense breasts.66American Cancer Society: Limitations of Mammograms Last revised July 23, 2026; screening mammograms miss about 1 in 8 breast cancers. An interval cancer is one diagnosed between screening rounds, either missed earlier or newly arisen.22US Preventive Services Task Force: Breast Cancer Screening Defines interval cancers as a mix of missed cancers and cancers emerging between rounds. How fast a cancer develops between screens is not something these sources put a figure on. Cancer Research UK says it is not possible to know whether a given cancer will grow quickly, slowly or not at all, and the NHS notes cancer can develop between appointments.77Cancer Research UK: Breast screening (mammography) Last reviewed 21 May 2026; says it is not possible to know whether a cancer will grow quickly, slowly or not at all.

That is why the NHS says a normal result does not guarantee you do not have, or will not develop, breast cancer.11NHS England: Your guide to NHS breast screening Crown copyright 2026; says a normal result is no guarantee and that cancer can develop between screening appointments. The National Cancer Institute also lists delayed diagnosis as a harm if a recent normal result leads someone to ignore symptoms.88National Cancer Institute: Breast Cancer Screening Opened October 2026; lists false positives, overdiagnosis, delayed diagnosis and radiation as potential harms. See breast changes to tell a doctor about.

Anxiety and radiation

The USPSTF names psychological harms such as anxiety or breast cancer specific worry after a false positive.22US Preventive Services Task Force: Breast Cancer Screening Harms of screening section: false positives can cause anxiety or cancer-specific worry. The radiation dose is small. The NHS says mammograms very slightly increase the chance of cancer over a lifetime, and that research shows the overall benefits outweigh the radiation risk.11NHS England: Your guide to NHS breast screening Crown copyright 2026; mammograms expose you to a small amount of radiation that very slightly increases lifetime cancer chance. The National Cancer Institute describes the risk as very low.88National Cancer Institute: Breast Cancer Screening Opened October 2026; radiation from mammography can potentially cause cancer, although the risk is very low.

Weighing it up

Age changes the balance, which is why guidelines differ; see what age to start, and stop, by guideline. The Canadian Task Force draft calls screening a personal choice, made with benefits and harms in absolute numbers.99Canadian Task Force on Preventive Health Care: Breast Cancer (Update), Draft Recommendations (2024) Archived draft; states that screening is a personal choice. For the full picture, start from the guide.