CAUSES, RISK FACTORS AND PREVENTION
Risk factors for ovarian cancer
The average Kiwi woman has a 1.6% chance of getting ovarian cancer in their lifetime. This means that 16 out of 1,000 women will get ovarian cancer at some point.
All women and people assigned female at birth are at risk of developing ovarian cancer. If you have had your fallopian tubes and ovaries removed, your risk is lower but not zero.
A risk factor is anything that makes it more likely a person will get ovarian cancer. Most of the time, there is no obvious cause or reason why someone develops ovarian cancer which is why it is important for everyone to know the symptoms. However, some people have genetic risk factors that make ovarian cancer much more likely.
Inherited genetic risk factors and your family history
Certain inherited genetic changes (mutations) can significantly increase your chance of getting ovarian cancer. You can inherit these changes from either your mother or father’s side of the family.
If you have a personal or family history of cancer ask your GP if you should consider genetic testing. If testing finds a genetic risk factor, there may be things you can do to reduce your risk.
10-15% of all ovarian cancers are caused by an inherited genetic mutation. The most common conditions are BRCA mutations and Lynch Syndrome.
BRCA mutations
Mutations in the BRCA 1 or BRCA 2 gene are more common if you have a personal or family history of:
- Breast cancer
- Ovarian cancer
- Pancreatic cancer
- Ashkenazi Jewish ancestry
The lifetime risk of developing ovarian cancer with a BRCA 1 mutation is 39-58%. This means that for every 100 women, 39-58 will develop ovarian cancer.
The lifetime risk for BRCA 2 is 13-29%. For every 100 women, 13-29 get ovarian cancer.
Lynch Syndrome
- Lynch Syndrome is more common if you have a personal or family history of:
- Colorectal (bowel) cancer
- Uterine cancer
- Ovarian cancer
- Kidney cancer
- Stomach cancer
- Liver cancer
- Brain cancer
Some people with Lynch Syndrome have a normal risk of ovarian cancer. Others have up to a 38% chance of getting ovarian cancer in their lifetime. The risk depends on the specific gene affected.
Age and the risk of ovarian cancer
As you age, your risk of getting ovarian cancer increases. Half of all people with ovarian cancer are 65 years or older. However, people of all ages can get ovarian cancer, including children.
In general, one in eight people diagnosed with ovarian cancer are younger than 45 years. But Maōri and Pacific people are more likely to get ovarian cancer younger with one in three diagnosed under 45 years.
Other ovarian cancer risk factors
Some risk factors only increase the chance of getting ovarian cancer by a small amount. If you have any of the following, your chances of getting ovarian cancer is still low, at less than 3%.
- Obesity
- Hormonal Replacement Therapy use
- Never having used an oral contraceptive pill
- Diabetes (but people who take metformin have lower than average risk)
- Endometriosis (increases the risk of clear cell and endometrioid ovarian cancer)
- Cigarette smoking (increases the risk of mucinous ovarian cancer/borderline tumours)
Ways to reduce the risk of ovarian cancer
Ovarian cancer is one of the least preventable cancers. Unlike cervical cancer, there is no screening test or vaccination for ovarian cancer. The main way to reduce ovarian cancer risk is with surgery.
Risk reducing surgery
Surgery is not suitable for most people. Removal of the ovaries (oophorectomy) and/or fallopian tubes (salpingectomy) is a major procedure. The risks from surgery usually outweigh the benefits. This is because most people’s chance of getting ovarian cancer is low, and every surgery has risks, even if they are small.
There are two specific situations where risk-reducing surgery can be worthwhile.
Hereditary ovarian cancer prevention
If you have a known genetic condition that increases your risk of ovarian cancer, your doctor may recommend surgery. During surgery, the fallopian tubes and ovaries are removed. This is called a bilateral salpingo-oophorectomy.
Surgery can reduce the risk of inherited ovarian cancer by 80-90%. If you have a BRCA 1 mutation this would mean your lifetime risk of ovarian cancer would be 3-4% or less after surgery.
If you still get periods, removal of the ovaries will cause infertility and menopause.
Although there is evidence the combined oral contraceptive pill can reduce the ovarian cancer risk, it is significantly less effective than surgery to remove the ovaries and fallopian tubes and it is not recommended for cancer prevention.
Opportunistic surgery to prevent ovarian cancer
If you need gynaecological or abdominal surgery for another reason, you may be able to have your fallopian tubes removed at the same time. This is called an opportunistic salpingectomy. Because you are already having surgery, the risks of this procedure are usually very low.
Fallopian tube removal reduces your chance of getting high-grade serous ovarian cancer. This is the most common type of ovarian cancer and it usually starts in the fallopian tubes. Because the ovaries are not removed, this surgery does not cause menopause but can cause infertility.
If you are considering surgery as a form of permanent contraception – fallopian tube removal is usually recommended over ‘tying’ or ‘clipping’ the tubes because it is better at reducing ovarian cancer risk.
If you need gynaecological/abdominal surgery, ask if removing the fallopian tubes to reduce your risk of ovarian cancer is an option.
Find out more about opportunistic salpingectomy.
Further Info:
Surgery to prevent ovarian cancer webinar (Ovarian Cancer Canada, 2024)
Note: this content has been reviewed by a gynaecological cancer specialist in New Zealand. Information is provided for general use and should not be a substitute for professional medical advice.
Last reviewed: 16 January 2024