Taking HRT and family history of breast cancer

How do I know if I might be at risk of having a gene that causes breast cancer?

Based on your family history, your risk of getting breast cancer can be classified into one of three groups:

General population risk: This means that, based on your family history, your risk of getting breast cancer, is the same or comparable to that of the general population. If only one person in your family has been diagnosed with breast cancer over the age of 40 years for example, you are likely to be at general population risk. General population risk is usually taken to be 1 in 8 – that is one person in every 8 will be diagnosed as having breast cancer at some time in their life.

Moderate risk: This means that, based on your family history, your risk of getting breast cancer, is higher than that of the general population and is usually taken to be 1 in 6 lifetime risk rather than 1 in 8. It is however still more likely that you will not get breast cancer due to your family history. If you have several family members who have been diagnosed with breast cancer over the age of 40 years or one close relative who developed breast cancer under the age of 40 years, you are likely to be at moderate risk.

High risk: This means that, based on your family history, your risk of getting breast cancer is higher than those in the moderate risk group. If you have several close relatives diagnosed with breast cancer or ovarian cancer under the age of 40 years you are likely to be at high risk. If you are considered high risk, you have an increased risk of getting breast cancer, but this does not mean you will definitely get it. A high risk is usually given as a 1 in 4 lifetime risk.

What are some of the altered genes called that can cause breast cancer?

The most common genes that increase the risk of breast cancer are the BRCA1, BRCA2 and TP53 gene. Women who have inherited one of these genes are considered high risk.

When should I be referred to be assessed for a genetic cause of breast cancer?

If you are concerned about your family history you should talk with a healthcare professional. If your family history suggests that you are at moderate or high risk then you should be referred directly to a genetics team. 

A moderate or high-risk family history includes any of the following:

• One first-degree* female relative diagnosed with breast cancer under the age of 40 years.
• One first-degree male relative diagnosed with breast cancer at any age.
• One first-degree relative with bilateral breast cancer diagnosed under the age of 50 years. Bilateral breast cancer means that both breasts were affected.
• Two first-degree relatives, or one first-degree and one second-degree** relative, diagnosed with breast cancer at any age.
• One first-degree or second-degree relative diagnosed with breast cancer at any age and one first-degree or second-degree relative diagnosed with ovarian cancer at any age (one of these should be a first-degree relative).
• Three first-degree or second-degree relatives diagnosed with breast cancer at any age.
• If an altered gene (for example BRCA1, BRCA2 or TP53 gene) has been identified in the family.

* First-degree relatives include your mother, father, brothers, sisters and your children.

** Second-degree relatives include aunts, uncles, grandparents, nieces and nephews.

What about HRT?

Women at population risk:

If your risk of getting breast cancer is considered the same or very similar to the general population risk then you can choose to take HRT just like the rest of the population. There is evidence to suggest that oestrogen plus Micronised Progesterone (Utrogestan) does not increase the risk of getting breast cancer for women at population risk in their fifties when it is taken for up to five years of use and this type of HRT is considered a low-risk option if you were to take HRT.

Women at moderate or high risk:

If your risk of getting breast cancer is considered moderate or high risk based on your family history, then the decision to take HRT can feel harder. At the moment there are not a lot of good quality studies on this topic. However, the studies that are available suggest that although HRT does not cause breast cells to become cancerous it may promote the growth of cancer cells that are already present. Importantly, this means that the natural history of breast cancer is not affected by the use of HRT. But, if breast cancer cells were to develop, due to having an increased heritable risk, HRT may promote the growth of these cancer cells further.

The general thinking, therefore, is that the risk of getting breast cancer is not increased by taking HRT. In other words, if an individual gets breast cancer, due to their family history, they were always likely to develop it. However, the absolute number of breast cancer cases will be increased by taking HRT in those women considered moderate or high risk and this is potentially because of its growth-promoting effect. 

Again, taking oestrogen plus micronised progesterone (Utrogestan) is the lowest risk option for taking HRT in terms of the risk of breast cancer, so this would be a better option if your risk is higher than population risk. It is worth noting that the evidence showing minimal risk of breast cancer from taking this form of HRT was from a normal healthy population, and it has not been closely studied specifically on women who are at higher risk of breast cancer.

What impact do lifestyle factors have?

There are lifestyle factors that affect the risk of breast cancer more significantly than taking HRT – such as being obese (Body Mass Index over 30), or drinking an average of 2 units of alcohol a day (equivalent to a small glass of wine) – and these factors should also be taken into account when making a decision about what to do.

Summary 

Menopause care is not one size fits all and the decision of whether or not to take HRT is a personal one for you. Some women with a higher than-population risk of breast cancer will choose to take alternatives to HRT to help manage their symptoms as they may feel anxious about their risk. Others will take HRT as it is the most effective way of managing symptoms and for them, the benefits of taking HRT are greater than any anxiety they may feel.