While most women in the UK have a one in 54 chance of developing ovarian cancer in their lifetime, for those who inherit faulty genes, like Angelina Jolie, the risk increases to one in two. If women know they have BRCA gene mutations, they can choose to take action before cancer develops.

But weighing the risk of cancer that might never grow against the very real trauma of surgery to remove healthy tissue as a preventive measure is an incredibly difficult conundrum, as Angelina Jolie explains.

BRCA1 and BRCA2 are genes that help repair damage to the DNA in our cells. If people inherit a mutated version of either of these genes it puts them at greater risk of certain cancers. Jolie learned some time ago that she had inherited a faulty BRCA1 gene from her mother. She had already lost her mother, grandmother and aunt to cancer, which alerted doctors that she might also be at risk.

In the UK, around one in every 500 people will carry a BRCA mutation. Generally, experts only recommend screening if a person has a strong family history of breast or ovarian cancer. For women carriers of BRCA1, it means their lifetime risk of breast cancer will range from 65-85% and their risk of ovarian cancer from 40-50%.

Her doctors advised that she should have this surgery about a decade before the earliest onset of cancer in her female relatives. Her mother’s ovarian cancer was diagnosed when she was 49. Jolie is now 39. Surgery does not completely guarantee that cancer will not develop – it is impossible to remove all of the at-risk tissue.

And there are side effects to consider – taking out the ovaries removes a woman’s fertility and puts her into the menopause, for example. Faulty BRCA genes are responsible for around 5% of all breast cancer cases and 10% of ovarian cancers, meaning the rest are caused by other factors.