HRT and breast cancer risk: the numbers, not the headlines

Breast cancer is the risk most people think of first when HRT comes up. It is usually reported as a percentage increase, which sounds alarming and says nothing about how many people are actually affected. NICE publishes the counts.

This article describes what that guidance says. It applies to people without a personal history of breast cancer. It is not advice about your own treatment, which is a conversation for you and your clinician.

The short version

Combined HRT, oestrogen with a progestogen, increases breast cancer risk. Oestrogen-only HRT, used after a hysterectomy, causes very little or no increase ¹. The increase with combined HRT grows the longer it is taken, and falls after stopping, but some of it persists for at least 10 years ¹.

The numbers for combined HRT

NICE's discussion aid counts new breast cancers among 1,000 women between the ages of 50 and 69 ²:

• 59 in 1,000 who never take HRT
• 79 in 1,000 who take combined HRT for 5 years from age 50, which is 20 more
• 92 in 1,000 who take combined HRT for 10 years from age 50, which is 33 more

Put the other way round, 921 of 1,000 women who take combined HRT for five years do not develop breast cancer over those 20 years, compared with 941 who never take it ². These figures combine sequential and continuous combined HRT ².

For women with early menopause who take combined HRT for 10 years from age 40, NICE counts 51 in 1,000 between the ages of 40 and 59, against 33 in 1,000 who never take it, which is 18 more ².

The numbers for oestrogen-only HRT

Between the ages of 50 and 69, NICE counts ²:

• 59 in 1,000 who never take HRT
• 69 in 1,000 who take oestrogen-only HRT for 5 years from age 50, which is 10 more
• 71 in 1,000 who take it for 10 years, which is 12 more

NICE describes this as very little or no increase, with little or no increase in the risk of dying from breast cancer ¹.

Why figures differ between sources

The NHS gives a smaller figure: around 5 extra cases in every 1,000 women who take combined HRT for 5 years ³. NICE's counts are higher partly because they run over 20 years, which includes the years after stopping, when NICE says the raised risk persists ¹². When comparing numbers, it helps to check what time period they cover.

What makes the risk higher or lower

NICE sets out the pattern for combined HRT ¹:

• the increase rises with how long HRT is taken
• it is higher in people currently taking HRT than in past users
• it declines after stopping but persists at least 10 years
• sequential combined HRT carries a lower risk than continuous combined, but higher than no HRT

NICE also says there is a very small increase in the risk of dying from breast cancer with combined HRT ¹.

On the type of hormone, NICE says breast cancer risk is similar with oestradiol and conjugated equine oestrogen in oestrogen-only HRT ¹. Whether micronised progesterone or dydrogesterone carries a different risk from other progestogens is not established, because the evidence is insufficient ¹.

The wider picture

Breast cancer is one outcome among several. NICE says that, overall, life expectancy is unlikely to change with either combined or oestrogen-only HRT ¹. NICE also notes that breast cancer risk varies with each person's own risk factors, some of which can be changed and some of which cannot ¹. The guide to what the HRT guidelines say on this site covers the other benefits and risks.

If you have had breast cancer

These numbers do not apply. NICE recommends that people with a personal history of breast cancer, or at high risk of it, are offered information on all their options and referral to a healthcare professional with expertise in menopause ¹, and that systemic HRT is stopped if breast cancer is diagnosed ¹.

Guidance in the US and Europe

The largest analysis of the worldwide evidence, pooling studies from many countries, reached similar numbers. It found that every type of hormone therapy except vaginal oestrogen was associated with some excess breast cancer risk, rising with duration and greater for combined than oestrogen-only preparations ⁴. It estimated that five years of hormone therapy from age 50 would add about one breast cancer between 50 and 69 for every 50 users of oestrogen with a daily progestogen, one in every 70 users with an intermittent progestogen, and one in every 200 users of oestrogen alone, with about twice those excesses after ten years ⁴. One in 50 is 20 in 1,000, the same as NICE's figure.

In the US, the FDA approved label changes in February 2026 that remove breast cancer from the boxed warning on hormone therapy products ⁵. The risk itself is still described in the research above. In Europe, the European Menopause and Andropause Society (EMAS) says treatment decisions should take account of each woman's personal and family risk profile ⁶.

What is still uncertain

The numbers are averages from large observational studies. NICE presents them as estimates to support a conversation, not a prediction for one person ².

Taking the numbers to an appointment

The useful question is not "is HRT safe" but "what are the numbers for someone like me, with the type of HRT you would suggest, for the length of time we expect". Writing it down beforehand makes it easier to ask.