Is breast cancer screening worth it?

Breast cancer screening has a proven benefit: mammography screening reduces breast cancer mortality. European guidelines assume a reduction of at least 20% over thirty years. A large overview of 28 systematic reviews shows estimates ranging from a 49% reduction in mortality to virtually no effect, depending on study design and age group. The overall trend points to a reduction in mortality, but most of the underlying reviews are judged as being at high methodological risk of bias. For the average woman of screening age, this benefit is real, although its precise magnitude is uncertain.

Set against this is a serious drawback: false positives and overdiagnosis. False positives are false alarms that lead to unnecessary follow-up investigations and anxiety. Overdiagnosis means that a detected tumour would never have caused symptoms in that woman's lifetime, yet it is still treated. These are recognised limitations of the current 'one size fits all' programme, in which every woman receives the same invitation regardless of her personal risk.

In older women the balance is less favourable. Research in women aged 70 and over shows that in the 70-to-74 age group approximately 31% of cancers detected through screening may represent overdiagnosis; in women aged 75 to 84 this rises to 47%, and above the age of 85 to well over half. At the same time, this research found no statistically significant reduction in mortality in these older age groups. It follows that the weighing of benefits and harms for women above the age of 75 is fundamentally different from that for younger women. The study does have methodological limitations, so the precise figures should be read with some caution.

For women with dense breast tissue, supplemental MRI screening offers a clear advantage. Following a negative mammogram, MRI detected an average of 1.52 additional cancers per 1,000 screening rounds, significantly more than ultrasound or tomosynthesis. MRI is therefore recommended as a supplement for women with a high risk or extremely dense breast tissue. This is not a replacement for routine screening, but a targeted extension for a specific group.

The future of screening likely lies in personalisation using artificial intelligence (AI). A randomised trial (ScreenTrustMRI) showed that an AI model could select the 6.9% of women with the highest risk after a negative mammogram for supplemental MRI. This yielded nearly four times more detected cancers per MRI performed compared with selection based on breast density alone, bringing the cost per cancer detected in line with that of standard mammography screening. A modelling study for the UK programme calculated that AI-driven personalisation of the screening interval (more frequent for high risk, less frequent for low risk) is expected to produce both health gains and cost savings. These are, however, model calculations; prospective research in practice is needed to confirm this.

Finally, accessibility is a point of attention. The uptake of breast cancer screening is suboptimal, particularly among uninsured women. A programme that works on paper only achieves its full effect when vulnerable groups are reached as well.