New Study Links High Prolactin Levels to 20% Increased Breast Cancer Risk in Post-Menopausal Women

New Study Links High Prolactin Levels to 20% Increased Breast Cancer Risk in Post-Menopausal Women

(IN BRIEF) A landmark international study has provided robust evidence that elevated levels of prolactin, a hormone involved in breast development, increase the risk of breast cancer in post-menopausal women. Researchers from The Institute of Cancer Research in London, along with colleagues from the UK, US, Canada, and Australia, analyzed data from 8,279 women using information from five cohort studies within the B2Risk consortium. The study found that women with high prolactin levels (above 13.15 ng/mL) experienced a 20% greater risk of invasive breast cancer compared to those with lower levels. The risk was particularly notable in women undergoing post-menopausal hormone therapy and in samples collected within ten years of diagnosis. Additionally, the association was stronger among women with lower BMI. These findings, while limited to post-menopausal women of European descent, offer valuable insights that could enhance personalized breast cancer risk assessments and inform future prevention strategies.

(PRESS RELEASE) LONDON, 3-Apr-2025 — /EuropaWire/ — In the most extensive study of its kind, researchers have uncovered compelling evidence that prolactin—a hormone integral to breast development—serves as a risk factor for breast cancer in post-menopausal women. By analyzing data from a large cohort, the team was able to pinpoint specific groups of women for whom elevated prolactin levels are most strongly linked to an increased risk of breast cancer. This breakthrough study, involving international collaboration among experts from the United Kingdom, United States, Canada, and Australia, promises to enhance our understanding of breast cancer causes and pave the way for improved risk prediction and preventative strategies.

Scientists at The Institute of Cancer Research (ICR) in London, in conjunction with several other institutions, pooled data from five cohort studies as part of the Biomarkers in Breast Cancer Risk Prediction (B2Risk) consortium. This effort provided detailed information on 8,279 post-menopausal women, who were initially free of breast cancer and aged on average between 60 and 67 years. Blood samples collected at the outset were used to measure plasma prolactin levels, while supplementary data on BMI, alcohol consumption, and breastfeeding history were gathered via questionnaires and medical records. Additionally, DNA from these samples was utilized to compute a polygenic risk score, and mammographic density was assessed from screening mammograms. Out of these participants, 3,441 were later diagnosed with invasive breast cancer.

The study revealed that women with lower prolactin levels (below 7.91 ng/mL) did not exhibit a heightened risk, whereas those with higher levels (above 13.15 ng/mL) faced about a 20% increased risk of developing breast cancer. Notably, the association was strongest among current users of post-menopausal hormone therapy (PMH), indicating that prolactin may interact with other hormones in influencing cancer risk. The timing of blood collection also played a role; samples taken within ten years of a cancer diagnosis showed a stronger link, suggesting that hormonal changes closer to disease onset are more predictive.

Furthermore, the study delved into how BMI might modify the effect of prolactin on breast cancer risk, finding that the association was more pronounced in women with lower BMI. Although the study is limited to post-menopausal women of European ancestry and based on a single prolactin measurement per individual, it marks a significant step towards personalized breast cancer prevention and risk assessment, with the potential to lead to earlier diagnosis and more targeted interventions.

Professor Montse Garcia-Closas, Group Leader in Integrative Cancer Epidemiology at ICR, stated, “Our findings deepen the evidence linking prolactin to post-menopausal breast cancer risk, enabling us to identify high-risk groups more accurately. This knowledge will be invaluable for refining breast cancer risk assessment models and may eventually guide new preventative or treatment strategies.” Dr. Simon Vincent, Director of Research, Support and Influencing at Breast Cancer Now, added, “Early identification through prolactin measurement could transform screening practices and improve treatment outcomes by facilitating earlier diagnosis. This study reinforces the need for ongoing research into the complex interplay between hormones, genetics, and environmental factors in breast cancer.”

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SOURCE: The Institute of Cancer Research