Hormone therapy in women under 55: latest data on breast cancer risks

Hormone replacement therapy (HRT) plays a key role in the management of women with severe menopausal symptoms or after surgical procedures that disrupt hormonal balance, such as hysterectomy or oophorectomy. The benefits of HRT include improved quality of life, reduced frequency of hot flashes, insomnia, osteopenia, and reduced risk of cardiovascular complications. However, the results of a recent study by the US National Institutes of Health (NIH) led by Dale Sandler and Kathy O’Brien, published in The Lancet Oncology, make important adjustments to the assessment of HRT safety for women under 55.

The researchers analyzed data from more than 459,000 women in Europe, North America, Asia, and Australia who received one of two main types of HRT: estrogen monotherapy (E-HT) or a combination of estrogen and progestin (EP-HT). It was found that E-HT is associated with a 14% reduction in the risk of developing breast cancer, while the use of EP-HT is associated with a 10% increase in this risk, and with a 18% increase for treatment lasting more than two years. Interestingly, the protective effect of E-HT was more pronounced among women who started therapy at a younger age and received it for a longer period of time. On the other hand, the risk associated with EP-HT increased particularly in women who had not undergone hysterectomy or oophorectomy.

It is worth noting that E-HT is usually prescribed only to patients after hysterectomy due to the increased risk of endometrial cancer with the uterus intact. Combined therapy, on the contrary, is used for women with an intact uterus, since progestin blocks the hyperplastic effect of estrogen on the endometrium. However, as a new analysis shows, this combination may be less safe in terms of breast cancer.

These findings are of particular clinical significance: according to statistics, more than 400,000 new cases of breast cancer are diagnosed in Europe each year. Cancer remains the most common cancer among women, and hormone replacement therapy is considered a risk factor, especially with long-term use. At the same time, in Europe, the proportion of women who need HRT is estimated at 20–30% of all those entering menopause.

The latest results emphasize the importance of a personalized approach to choosing the type of HRT. Women who have undergone hysterectomy should be given preference to estrogen monotherapy, which, according to new data, not only does not increase but may even reduce cancer risks. However, for women with an intact uterus, combination with progestin should be used with caution, especially when it comes to long-term treatment. In summary, these results do not call into question the value of HRT as a tool for improving the lives of women in menopause, but they do require careful assessment of the risks and benefits of each specific clinical case.

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Published: 05.07.2025

Updated: 06.07.2025

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak