Ovarian cancer and genetic testing
As a gynaecologic oncologist, I often get asked by patients and families if ovarian cancer runs in families or if it is genetically inherited. The answer is both yes, and no. Before I go into the genetics, I should first give a little background information on the disease.
Ovarian cancer is a rare disease. It affects about 1 in 100 women during their lifetime. This is compared to a lifetime risk of about 1 in 8 of developing breast cancer. By far and away, the most common cause of death in women from cancer in Australia is smoking related lung cancer. The problem with ovarian cancer is that, despite many advances in medicine, it remains a high mortality disease. Every year in Australia, about 1700 women are diagnosed with ovarian cancer and about 1000 women will die from the disease.
Ovarian cancer is a mixed bag of tumours. There are a group of cancers called germ cell tumours that tend to affect women between the ages of 15 and 25. These cancers are very rare and make up less than 1 in 10 ovarian cancers. They are highly curable with surgery and chemotherapy. Then there are the epithelial ovarian cancers. These are your “standard” ovarian cancers and make up about 80% of the burden of disease. It is a disease that tends to affect women after the menopause, generally around the age of 65. It is these cancers that we will focus on today.
Some epithelial ovarian cancers can be caused by defects in a woman’s genetic make up. These gene mutations, in general, are inherited from one of their parents. However, there may be no family history of cancer. Current science suggests that about 10% of epithelial ovarian cancers are caused by a genetic mutation. That means that 90% are sporadic i.e. just plain bad luck. The most common genetic mutations that cause ovarian cancer are the BRCA (pronounced “brakka”) 1 and BRCA 2 gene mutations and a group of gene defects that cause a cluster of cancers known as Lynch syndrome. The BRCA 1 and 2 gene mutations have been given much publicity by the actress, Angelina Jolie. They predispose women and men to developing ovarian AND breast cancer. Women with BRCA1 and 2 gene mutations have a 40 and 20% respectively life time risk of developing ovarian cancer.
Women with Lynch syndrome have a 10% chance of developing ovarian cancer. However, they also have up to a 50% chance of bowel cancer and a 40% chance of uterine cancer.
Unfortunately, there is no effective screening test for ovarian cancer. As part of my role as a surgeon looking after women with ovarian cancer, I refer women diagnosed with ovarian cancer for genetic testing. I also counsel women who find themselves with a genetic risk of ovarian cancer and offer them risk reducing surgery depending on the genetic defect they carry. Risk reducing surgery usually involves a keyhole operation to remove the Fallopian tubes/ovaries +/- the uterus after women have completed their families. That is usually after the age of 35 for women with the BRCA1 gene and 40 for women with BRCA2 or Lynch. Risk reducing surgery decreases a woman’s risk of developing ovarian cancer by 95%. It also decreases their risk of developing breast cancer by about half! Counselling and risk reducing surgery should be done by a gynaecologic oncologist as there is a small chance of finding that a woman already has ovarian cancer at the time of her surgery. That needs to be managed by a gynaecologic oncologist and is included in pre-op counselling.
So in summary, ovarian cancer is a rare disease but it is a high mortality disease. Unfortunately there is no effective screening test for ovarian cancer. The vast majority of women with ovarian cancer are sporadic cases and have been very unlucky. Approximately 1 in 10 women with ovarian cancer have inherited a gene that predisposes them to the disease. Women diagnosed with ovarian cancer are offered genetic testing, if they wish, by a specialist such as myself. Women with a genetic predisposition to ovarian cancer should be offered risk reducing surgery, when appropriate. Risk reducing surgery is usually minimally invasive and radically reduces a woman’s risk of both ovarian and breast cancer.
If you would like more information, I recently co-authored an article on hereditary ovarian cancers with that is available HERE.