Recommendations on population screening
Population mammography screening recommendations (for women with average risk) differ between countries and agencies, reflecting persistent non-consensus on the magnitude of benefit (mortality reduction) and harms (in particular, the extent of overdiagnosis), and how these outcomes balance out overall and in specific age groups.
This is exemplified in selected recommendations:
• The US Preventive Services Task Force recommends screening every 2 years for women aged 50–74 years, and emphasizes individualized decisions for those aged 40–49 years that take account of the woman’s values
• Canadian guidelines support shared decisions, do not recommend screening for women aged 40–49 years and recommend screening every 2–3 years for women aged 50–69 years
• The American Cancer Society recommends annual screening for women aged 40–54 years, and a transition to 2-yearly screening for those aged ≥55 years (with the opportunity to continue annual screening)
• The International Agency for Research on Cancer reports that there is sufficient evidence that screening confers benefit in women aged 50–74 years (but limited evidence in the 40–49 years age group) and that there is sufficient evidence that mammography detects breast cancers that would never have been diagnosed or would never have caused harm if women had not been screened (overdiagnosis)
• European recommendations specify mammography through organized screening programmes every 2–3 years in women aged 45–74 years (and suggest against annual screening)
Women at average risk do not have a pre-existing breast cancer or a previous diagnosis of a high-risk breast lesion (such as atypical ductal hyperplasia), and do not harbour arisk-enhancing genetic mutation (such as BRCA1 or BRCA2 mutations or other familial breast cancer syndromes).