Whether the benefits of routine annual breast screening for women aged 40-49 years outweigh the harms and costs is still unclear, according to an Article published in this week’s issue of The Lancet.
Previous research has suggested that inviting women for screening between the ages of 40-49 years may be beneficial. However, this benefit could be due in part to women who were invited in their 40s but were actually screened after they were 50. Dr Sue Moss (The Institute of Cancer Research, London, UK) and colleagues designed the AGE trial to overcome this issue by only inviting women for annual mammography up to age 48.
Researchers randomly allocated over 160 900 women to receive annual mammography invitations starting at age 40 years or invitations starting at 50 years of age as in the current NHS Breast Screening Programme. The trial was undertaken in 23 NHS breast-screening units in England, Wales, and Scotland. Women were followed-up for an average of 11 years.
The investigators found that though breast cancer mortality dropped by 17% in the younger age screening group compared with the control group this was not a statistically significant result. They also found that out of 17 030 regular attenders, 23% had at least one false positive result compared with an estimated 12% of women older than 50 years screened regularly as part of the national screening programme. Other possible harmful effects of screening include the risk of radiation-induced breast cancer. However, the authors estimate that the percentage of women for whom the risk of radiation-induced breast cancer might outweigh the benefit will be very small.
The authors add that the later screens in the trial took place at 7-8 years from date of entry, and the effect of these screens is unlikely to have emerged yet.
"Future decisions on screening policy should be informed by further follow-up from this trial and should take into account the possible harms and costs as well as benefits," they conclude.
In an accompanying Comment Benjamin Djulbegovic (H. Lee Moffitt Cancer Center & Research Institute, Tampa, Florida, USA) states: "…the decision of whether to recommend screening mammography crucially depends on estimates of harm, which will never be zero. Although the best estimates of harms from screening mammography seem to be less than the benefits, they remain too uncertain to conclude that screening mammography in this age-group is associated with a net benefit. Benefit and harms need to be contrasted with each woman’s individual risks for development of breast cancer. Every woman, with her physician’s guidance, should decide whether regret will be greater if she develops breast cancer that could have been detected earlier by screening mammography, or if she develops breast cancer later in life as a result of screening mammography itself." (Quote by e-mail; exact version does not appear in published Comment)
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