Women taking certain kinds of HRT could have a higher risk of developing breast cancer - the study explained

Women taking the most common form of hormone replacement therapy (HRT) are at a higher risk of developing breast cancer than previously thought, according to a new study.

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HRT is a treatment administered to relieve symptoms of the menopause, replacing hormones that are at a lower level for those approaching it.

Link between use of HRT and risk of breast cancer

The recent study involved scientists from the universities of Nottingham and Oxford analysing HRT prescriptions for more than 98,000 women aged 50 to 79, who were later diagnosed with breast cancer.

Alongside this, the research also looked at the prescriptions of more than 457,000 women of the same age who did not develop the disease.

Findings suggest that the women who recently took oestrogen-only HRT for five or more years were 15 per cent more likely to develop breast cancer, compared with those who were never prescribed the replacement therapy.

However, over the same time period, combined oestrogen-progesterone HRT (which is the most common form over the therapy) was associated with a 79 per cent increased risk of breast cancer.

The NHS explains that there are different HRT hormones, but most women take a combination of the hormones oestrogen and progestogen. Women who do not have a womb can take oestrogen on its own.

The scientists analysed two primary care databases linked to hospital records in order to compare HRT prescriptions among women of the same age from the same GP surgery, some of which developed breast cancer.

The study found that oestrogen-only HRT was not linked to breast cancer among those who took the therapy five or more years ago, with the duration of their treatment also lasting five or more years.

Previous short-term use of oestrogen-progesterone - which is defined as taking the therapy five or more years ago for a period of less than five years - was also not linked to an increased risk of breast cancer.

However, those who took oestrogen-progestogen five or more years ago for a period of five or more years, were found to be 16 per cent more likely to develop the disease.

The study, which was published in the The British Medical Journal (BMJ), says, “This study has produced new generalisable estimates of the increased risks of breast cancer associated with use of different hormone replacement preparations in the UK.

“The levels of risks varied between types of HRT, with higher risks for combined treatments and for longer duration of use.”

Who can be prescribed HRT?

Most women can take HRT if they're having symptoms associated with the menopause, but it may not be suitable if you have certain medical conditions, including a history of breast cancer, ovarian cancer or womb cancer, or a history of blood clots.

HRT can cause side effects, but these will usually pass within three months of starting treatment.

Common side effects include:

  • breast tenderness
  • headaches
  • feeling sick
  • indigestion
  • abdominal (tummy) pain
  • vaginal bleeding

What is the menopause?

The menopause is a natural part of aging that usually occurs between the age of 45 and 55, as a woman's oestrogen levels decline. In the UK, the average age for a woman to reach the menopause is 51.

Periods usually start to become less frequent over a few months or years before they stop altogether, but sometimes they can stop suddenly.

The NHS notes that around eight in every 10 women will have additional symptoms for some time before and after their periods stop. Common symptoms include hot flushes, night sweats, problems with memory and concentration, and headaches.