Could science predict who will get breast cancer?

Professor Amy Berrington

Co-Principal Investigator, Generations Study, The Institute of Cancer Research, London

Professor Montserrat Garcia-Closas

Co-Principal Investigator, Generations Study, The Institute of Cancer Research, London

For over two decades, a team of scientists have been quietly transforming our understanding of breast cancer.

The Breast Cancer Now Generations Study, launched in 2004 and led by scientists at The Institute of Cancer Research, London, has followed more than 110,000 UK women, collecting half a million questionnaires and thousands of blood samples to uncover the complex factors behind the disease.

Now in its 21st year, the study has helped identify hundreds of genetic changes linked to breast cancer and revealed how lifestyle and hormonal factors contribute to risk. These insights are being used to develop tools that predict which women are most at risk, enabling earlier detection and prevention strategies.

Uncovering genetic risks of breast cancer

One major breakthrough of the study is the development of a genetic risk score based on more than 300 single-nucleotide polymorphisms (SNPs), tiny differences in DNA which can help explain why people respond differently to medicines or have different risks for certain diseases. While each SNP has a small effect, together, they can significantly increase someone’s risk – even in women without a family history of breast cancer.

Impact of family history

The study also refined how family history is assessed, factoring in the number and age of female relatives to offer more accurate predictions. Other findings show that early menstruation, influenced by factors like childhood weight and maternal smoking, raises breast cancer risk due to longer exposure to hormones.

Smoking has been linked to a
14% higher risk of breast cancer.

Risks of smoking

Smoking has been linked to a 14% higher risk of breast cancer, rising to 24% for those who started before age 17. For women with a family history, smoking increases risk by 35%. Conversely, physical activity – even light exercise – can modestly reduce risk, especially in younger women.

Understanding lifestyle factors

Pregnancy lowers long-term breast cancer risk, though there’s a slight increase in aggressive cancer types shortly after childbirth. Menopausal age also plays a role, with earlier menopause linked to lower risk. Lifestyle factors like smoking and weight gain influence when menopause occurs. Finally, weight loss in postmenopausal women has been shown to reduce levels of hormones associated with breast cancer, suggesting that maintaining a healthy weight could be a key preventative measure.