Genetics Background:

In Ireland, the average lifetime risk of developing ovarian cancer is ~ 1.2% with approximately 350 cases diagnosed per annum.

 

It has been estimated that 5 to 10% of cases are due to inheriting a gene from one of your parents. It is hoped that identification and screening of this high-risk group with the inherited gene will reduce the mortality from ovarian cancer.

 

What types of inherited ovarian cancers are there?

- BRCA1 (Breast Cancer 1) and BRCA2 (Breast Cancer 2) genes.

 

Women with heritable BRCA 1 mutations have a 35% to 60% chance of developing a BRCA-associated gynaecologic (ovarian, fallopian tube or primary peritoneal) cancer by age 70, women with germline BRCA 2 mutations have a 10% to 27% chance of developing a BRCA-associated gynaecologic malignancy by age 70.

 

Women with mutations in either of these tumour suppressor genes are also at a greatly increased risk of breast cancer, with 56% to 84% of mutation carriers developing breast cancer by age 70.

 

-Lynch syndrome or Hereditary Non Polyposis Colorectal Cancer (HNPCC), ovarian cancer is associated with colorectal, endometrial, gastric and uro-epithelial mlignancies.

 

Lynch syndrome is caused by mutations or misspellings on DNA mismatch repair (MMR) genes and is associated with a 9-11% lifetime risk of ovarian cancer.

 

Cancer Genetics Clinics:

Cancer genetic clinics are run in

  • National Centre for Medical Genetics (NCMG) in Our Lady’s Children’s Hospital, Crumlin (with satellite clinics in Cork and Galway)
  • St. James’s Hospital (SJH)
  • The Mater Misericordiae University Hospital (MMUH).

 

Referrals should be addressed to Professor Andrew Green in NCMG and Dr. David Gallagher in SJH and MMUH.

A cancer genetics clinic is also run in the Mater private hospital.

Referral of the ovarian cancer patient:

Referral for cancer genetic risk assessment and consideration of diagnostic genetic testing may be warranted for all patients with epithelial ovarian cancer and this recommendation is even more compelling if there is a family history of cancer.

 

Various clinical criteria for referral to cancer genetics services incorporate age of onset of breast cancer diagnosis, ovarian cancer diagnoses (not considering age of onset), and number of close relatives (first, second or third degree) with breast and/or ovarian cancer.

 

Specific criteria are available on the National Centre for Medical Genetics website  for hereditary breast and ovarian cancer

Referral for cancer genetic risk assessment should not be strictly limited to those individuals who meet high-risk criteria as certain features may mask the dominant expression of the BRCA genes, including incomplete or inaccurate reporting of family medical history information, family members undergoing surgical removal of target organs (i.e., ovaries) for benign conditions, and family structure such as small family size with few at-risk relatives.

 

In addition BRCA1/2 mutations can be inherited from either the mother or father, and paternal transmission of a hereditary predisposition to breast and ovarian cancer may be masked by the relatively low cancer risk for male.

 

Lynch syndrome criteria are available on the National Centre for Medical Genetics website

 

Effect of ovarian cancer subtype and age of diagnosis on risk estimation: Accurate risk estimation in ovarian cancer families requires confirmation of the type of ovarian cancer you have as some types are not associated with an increased risk. While earlier age of diagnosis is an additional risk factor, it is not as great as for breast cancer. This may be partly due to the fact that ovarian cancer is rare before 40 years of age in BRCA1 mutation carriers and 50 years in BRCA2 and appears to occur at an almost equal frequency in BRCA1/2 carriers from those ages.
Other genes predisposing to ovarian malignancy

Other genes which predispose to ovarian cancer include the mismatch repair (MMR) genes, MSH2, MLH1, MSH6 and PMS2 which confer around a 12 per cent lifetime risk of ovarian cancer.

 

Ovarian cancer diagnosed < 30 years of age may be more likely to be due to MMR mutations than BRCA1/2.

 

Ovarian malignancy and other syndromes :

A number of inherited conditions have been linked to an increased risk of ovarian cancer, but in reality these links are to non-epithelial tumours.

 

Sex cord tumours are increased in Peutz-Jeghers syndrome.

 

Gorlin syndrome (naevoid basal cell carcinoma syndrome (NBCCS) is said to have an increased risk of ovarian cancer.

 

Will a positive genetic test have any influence on my life insurances/mortgages:

There is legislation enacted (Disability Act 2005) which protects individuals from discrimination based on genetic testing so individuals will not be asked if they or any 3rd party have had genetic testing

Screening and prevention options:

Efforts to screen for ovarian cancer is limited at the moment by the lack of effective screening tools. Preventive surgery has been shown to significantly reduce the risk of developing ovarian cancer.

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