Womens Health

Family History Important for Ovarian Cancer Risk

Frederick R. Jelovsek MD

Do you have a family history of ovarian cancer? Is a family history of breast, colon or endometrial cancer important in predicting risk to ovarian cancer? Yes it is.

Ovarian Cancer Risk

If one of your relatives has had ovarian cancer, this can raise your chance over the baseline risk:

  • the average woman has a 1% (1 in 70) lifetime risk of ovarian cancer
  • having one first degree relative with ovarian cancer (mother, sister or daughter) gives a 5% lifetime risk for ovarian cancer
  • having two first degree relatives increases the lifetime risk to 20-30%.

Randall TC, Rubin SC: Assessing a patient's risk for hereditary ovarian cancer. OBG Management 1998;Oct:37- 46, have examined the different risk factors for using a woman's family history of any cancer to determine if she is at risk for ovarian cancer. They report the general classification of hereditary ovarian cancer syndromes.

  • breast-ovarian cancer syndrome
  • Lynch syndrome in which family members may develop non polyposis-related colon or rectal carcinoma, endometrial carcinoma and in some cases, ovarian carcinoma
  • site-specific ovarian cancer

Causes of Ovarian Cancer

In the breast-ovarian cancer syndrome, about 90% of cases can be explained by mutation in two genes, BRCA1 and BRCA2. These are the two breast/ovarian cancer genes that have been identified to date.

Women who have these inherited genetic mutatations have as high as a 40-45% risk of ovarian cancer and as high as an 85% risk for breast cancer. If their relatives with breast or ovarian cancer have their disease onset at less than 50 years of age, or if they are of Ashkenazi Jewish heritage, that is even more suspicion that the family members carried the gene mutation.

In order to differentiate women who have a risk of an hereditary ovarian cancer syndrome (only about 5-10% of all ovarian cancers) versus just having relatives with cancer but no increased genetic risk, the following questions should be asked.

Family history of Increased ovarian cancer risk if...
ovarian cancer 1st degree relative (mother, daughter, sister) with ovarian cancer especially if age onset is less than 50
breast cancer 1st degree relative (mother, daughter, sister) with ovarian cancer especially if age onset is less than 50
any 1st or 2nd degree relative with a bilateral breast cancer
endometrial (uterine) cancer 1st degree relative (mother, daughter, sister) with ovarian cancer especially if age onset is less than 50
colon or rectal cancer if not arising in a polyp (nonpolyposis); this represents about 10-20% of all colorectal cancer
prostate cancer a 1st or 2nd degree relative with prostate cancer, especially at an early age, can sometimes have BRCA1 or BRCA2 gene mutations

Now What?

Well now that we've asked the questions and determined there is an increased risk for ovarian cancer, what are the next steps? With any increased risk due to family history, these authors reccomend:

  • establish a complete family history with medical records if possible
  • try to get genetic testing done on the family member with the cancer history if they are still alive
  • armed with all the information possible, obtain good genetic counseling
  • screen for early lesions using ultrasound and CA-125 starting at least 5 years before the earliest age of cancer onset in the family member
  • consider chemoprevention such as oral contraceptives which can reduce the risk of hereditary cancer by 50% or more
  • consider prophylactic removal of ovarian tissue only if the risk is proved to be substantial

Other Related Articles

How to tell if an Ovarian Mass is Malignant?
Hereditary Ovarian Cancer Reduced by Oral Contraceptives

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