Breast cancer is the second leading cause of death from cancer in women, but outcomes have been shown to improve if caught and treated early. This is why many countries around the world have set up breast cancer screening programmes, aiming to identify breast cancer at earlier stages of the disease, when treatment can be more successful.

However, interpreting mammograms (breast x-rays) remains challenging, as evidenced by the high variability of experts’ performance in detecting cancer. In this collaborative research with Google Health & Cancer Research UK Imperial Centre, Northwestern University, and Royal Surrey County Hospital now published in Nature, we developed an AI system capable of surpassing clinical specialists from the UK and US in predicting breast cancer from mammograms, as confirmed by biopsy.

Breast cancer screening datasets

Breast cancer screening programmes vary from country to country. In the US, women are typically screened every one to two years, and their mammograms are interpreted by a single radiologist. In the UK, women are screened every three years, but each mammogram is interpreted by two radiologists, with an arbitration process in case of disagreement. We utilised large datasets collected in both countries to develop and evaluate this AI system.

The UK evaluation dataset consisted of a random sample of 10% of all women with screening mammograms at two sites in London between 2012 and 2015. It included 25,856 women, 785 of which had a biopsy, and 414 women with cancer that was diagnosed within three years of imaging. These de-identified data was collected as part of the OPTIMAM database effort by Cancer Research UK, and are subject to strict privacy constraints.

The US evaluation dataset consisted of de-identified screening mammograms of 3,097 women collected between 2001 and 2018 from one academic medical centre. We included images from all 1,511 women who were biopsied during this time period and a random subset of women who never underwent biopsy. Among the women who received a biopsy, 686 were diagnosed with cancer within 2 years of imaging.