Preventing breast cancer before it starts

Breast cancer prevention has long relied on major surgery or long-term hormone treatments for women at high risk. New research is now exploring a different approach: using an existing drug to block the hormone progesterone, with early findings suggesting it could help reduce breast cancer risk in younger, pre-menopausal women.

Breast cancer is the most common cancer affecting women worldwide. For those with a strong family history, the risk of developing the disease can be a constant worry from an early age.

Before the menopause, options to reduce that risk are limited. Women are often faced with a difficult choice between major preventative surgery or long-term hormone treatments, both of which can have lasting physical and emotional consequences.

There is a clear need for new approaches that can reduce breast cancer risk without such life-altering interventions.

Rethinking prevention

A recent study has explored whether breast cancer could be prevented before it starts by targeting a key hormone involved in its development. The research focused on progesterone, a hormone that plays an important role in the normal breast, but can also drive cancer risk.

Progesterone encourages the growth of certain breast cells that have the potential to turn into cancer. It also affects the structure of breast tissue itself, shaping the environment in which cells grow. Together, these effects can increase the likelihood that cancer will develop, particularly aggressive forms that are more common in younger women.

Researchers investigated whether blocking progesterone using ulipristal acetate, a drug already approved for other conditions, could reduce these risks.

Testing an existing drug

In the study, 24 women aged 34 to 44 with a family history of breast cancer took ulipristal acetate for 12 weeks. To understand how the drug affected the breast, participants underwent MRI scans, blood tests and breast biopsies before and after treatment.

The results were highly encouraging, demonstrating measurable improvements in several key indicators that scientists believe contribute to breast cancer risk.

MRI scans showed that breast tissue became less dense following treatment. This is important because higher breast density is one of the strongest known risk factors for breast cancer and can also make tumours harder to detect.

At a cellular level, researchers saw a reduction in the number of luminal progenitor cells - a group of cells that can develop into aggressive cancers, including triple-negative breast cancer. They also observed significant changes to collagen, the protein that gives breast tissue its structure. With treatment, the tissue became softer and less stiff, creating an environment that is less favourable for cancer to develop and grow.

"We are profoundly grateful to the women who volunteered for this study," says Dr Sacha Howell, Clinical Senior Lecturer in Breast Oncology at Manchester. "Our research, with them, provides evidence that progesterone plays a critical role in breast cancer development in high-risk individuals.

"By targeting its action, ulipristal acetate and other anti-progestins show promise as preventive treatments for women at increased risk."

A new direction for women at high risk

While this was a small, early-stage study, the findings point to a potential new direction for breast cancer prevention. A short course of an existing drug could one day offer women at higher risk a non-surgical option to help protect their health.

Larger and longer-term studies are now needed to confirm whether this approach can safely reduce breast cancer rates over time. If successful, it could transform prevention strategies and give women more choice, control and reassurance.

By focusing on prevention rather than treatment, this research highlights how understanding the biology of cancer risk can lead to practical solutions - offering hope that fewer women will face a breast cancer diagnosis in the future.