Why HRT is usually not an option after breast cancer

Hormone replacement therapy, often called HRT, uses oestrogen, sometimes combined with a progestogen, to relieve menopause symptoms such as hot flushes, night sweats and vaginal dryness. For most women without breast cancer, it is an effective treatment. After breast cancer, however, HRT is generally not recommended. The main reason is that most breast cancers are hormone receptor positive, meaning they use oestrogen and progesterone to grow. Giving these hormones could encourage any remaining cancer cells to grow. Research supports this concern. A randomised trial called HABITS, which gave HRT to women who had been treated for breast cancer, was stopped early because women taking HRT had a significantly higher rate of breast cancer returning. Another trial found less clear results, but overall guidelines recommend avoiding systemic HRT after breast cancer. The concern applies most strongly to hormone receptor positive cancer, but HRT is usually avoided after hormone receptor negative cancer too, because the long-term safety is uncertain. For women with severe symptoms that seriously affect quality of life and do not respond to other treatments, a specialist may occasionally discuss options after carefully weighing risks. Non-hormonal treatments, lifestyle changes and psychological approaches can help most women manage symptoms.

HRT can fuel hormone-sensitive cancer

Adding hormones may encourage remaining cancer cells to grow.

Effective alternatives exist

Non-hormonal medicines, CBT and vaginal moisturisers help many women.

Always ask first

Check with your oncologist before taking any hormone-containing product.

Many women consider herbal or natural products when HRT is not an option.

Plant oestrogens

Some supplements contain phytoestrogens such as soy isoflavones or red clover, which act like weak oestrogen. Their safety after breast cancer is uncertain.

Interactions

Some herbs can interact with hormone therapy or other medicines.

Dietary soy

Normal amounts of soy foods are generally considered safe, but concentrated supplements are different.

Ask before using

Always check with your oncologist or pharmacist before taking herbal products.

Advice about HRT after breast cancer is based on a small number of important trials and on what is known about how breast cancer grows.

The HABITS trial

This Scandinavian trial randomly assigned women who had been treated for breast cancer to HRT or no HRT. It was stopped early because women taking HRT had a clearly higher rate of new breast cancer events, including recurrence.

The Stockholm trial

A similar trial did not show the same increase, possibly because of differences in the women included and the type of HRT used. However, its results were not strong enough to reassure doctors.

What guidelines conclude

Taking both trials together, major guidelines advise against systemic HRT for most women after breast cancer.

Hormone therapy interactions

Hormone therapies such as aromatase inhibitors work by lowering oestrogen. Adding oestrogen would work directly against them.

Hormone-like alternatives

Some synthetic hormone-like medicines were also studied and were associated with higher recurrence, so they are generally avoided.

Ongoing research

Research continues into safer options for severe menopause symptoms in breast cancer survivors.