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Background

Up to 15% of all cases of invasive ovarian cancer involve the inheritance of a mutated gene.2 Women who have inherited mutations in the BRCA1 or BRCA2 genes have substantially elevated risk of ovarian and breast cancer, with estimated lifetime risk for ovarian cancer, ranging from 36% to 46% for BRCA1 mutation carriers and from 10% to 27% for BRCA2 mutation carriers.3-4 Women with Lynch Syndrome have an elevated risk of developing certain cancers, including an increased lifetime risk of ovarian cancer of up to 10%.5

As a group, women at potentially high risk of developing ovarian cancer have a risk more than three times the population average. Their risk of developing ovarian cancer up to age 75 is between 1 in 30 and 1 in 2,  depending on whether genetic test results are known.5 This group covers less than 1% of the female population.

Management options aim to reduce the risk of ovarian cancer in high-risk women. Options include surgery or preventive therapy (previously known as chemoprevention). Surgical options include risk-reducing salpingo-oophorectomy (RRSO), which may or may not be performed with a hysterectomy, and tubal ligation. There is increasing evidence that some of these cancers originate in the fimbrial end of the fallopian tube.6 The most effective risk-reducing strategy for ovarian cancer is bilateral salpingo- oophorectomy.7 Preventive therapy (use of the oral contraceptive pill (OCP)) may be an option for pre-menopausal women who choose not to have RRSO.5

There are several issues to be considered in the management options of women at high risk of ovarian cancer including factors influencing decision making, psychosocial wellbeing, surgical outcomes and quality of life.

There is no evidence that surveillance of women at high risk of ovarian cancer, using ultrasound or CA125, singly or in combination, is effective in detecting early ovarian cancer.7 

Designation of level of risk of ovarian cancer

A woman who has a gene fault in BRCA1 or BRCA2 (BRCA1/2) confirmed by genetic testing is at high risk of developing ovarian or breast cancer.3, 5, 8 A woman who has not had genetic testing but who has a strong family history5 of either ovarian or breast cancer may have a gene fault in BRCA1/2 and is considered potentially at high risk of developing ovarian or breast cancer. If a woman has a strong family history where an affected family member has had genetic testing for BRCA1/2 which was inconclusive she is still considered at potentially high risk, as there may be gene faults which affect her ovarian or breast cancer risk which are not currently tested for or not yet discovered. Women who do not have a strong family history or a confirmed gene fault are considered at average risk.9

A woman who has Lynch Syndrome (or HNPCC) confirmed by genetic testing is also at high risk of developing ovarian cancer, as well as endometrial cancer, colorectal cancer, gastric cancer and cancers involving the renal tract.5 A woman who has not had genetic testing but who has a strong family history of these cancers, suggestive of Lynch Syndrome, is considered potentially at high risk of developing ovarian cancer. A strong family history suggestive of Lynch Syndrome is considered to be three or more 1° or 2° degree relatives on the same side of the family diagnosed with colorectal cancer (particularly if diagnosed before the age of 50), endometrial cancer, ovarian cancer, gastric cancer, and cancers involving the renal tract.5

Definition of potentially high risk of ovarian cancer[#]

Women have been defined as being at potentially high risk of developing ovarian cancer if they:

  • Are a woman who is at high risk of breast cancer due to a gene fault e.g. in BRCA1 or BRCA2
  • Have one 1° or 2° relative diagnosed with epithelial ovarian cancer in a family of Ashkenazi  Jewish ancestry*
  • Have one 1° or 2° relative with ovarian cancer at any age, and another with breast cancer before the age of 50, where the women are 1° or 2° relatives of each other
  • Have two 1° or 2° relatives on the same side of the family diagnosed with epithelial ovarian cancer, especially if one or more of the following features occurs on the same side of the family:
    1. additional relative(s) with breast or ovarian cancer
    2. breast cancer diagnosed before the age of 40
    3. bilateral breast cancer
    4. breast and ovarian cancer in the same woman
    5. breast cancer in a male relative
  • Have three or more 1° or 2° relatives on the same side of the family diagnosed with a family history suggestive of Lynch Syndrome (or HNPCC) e.g. colorectal cancer (particularly if diagnosed before the age of 50), endometrial cancer, ovarian cancer, gastric cancer, and cancers involving the renal tract
  • Are a member of a family in which the presence of a high-risk ovarian cancer gene mutation has been established

If genetic test results are known, individual risk may be higher or lower. The category of potentially high risk of ovarian cancer covers less than 1% of the female population. As a group, lifetime risk of ovarian cancer ranges between 1 in 30 and 1 in 2. This risk is more than 3 times the population average.

* High-risk ovarian and breast cancer gene mutations are more common in people of Ashkenazi Jewish ancestry

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