Ovarian Cancer: Risk Factors

A number of genetic and non-genetic factors can increase the risk of ovarian cancer. These include:

Non-genetic risk factors

Ovarian cancer risk increases with age and is most commonly a cancer seen in postmenopausal women. Obesity has also been associated with an increased risk of ovarian cancer. A number of hormonal treatments may be associated with an increased risk of ovarian cancer. The fertility drug clomiphene citrate used for long periods of time (greater than one year) may increase the risk of ovarian cancer. Similarly, postmenopausal hormonal replacement therapy, particularly estrogen alone, may increase the risk of ovarian cancer.

There are also a number of factors that are protective against ovarian cancer. The risk of ovarian cancer is lowered in women taking birth control pills (oral contraceptive pills). The reduced is risk of ovarian cancer may be seen after only 3 months of use. Five years of oral contraceptive pill use reduces the risk of ovarian cancer by 50%. In addition to birth control pills, depot medroxyprogesterone acetate (DMPA) may reduce the risk of ovarian cancer. Other protective factors against ovarian cancer include pregnancy and tubal ligation (having your tubes tied). Finally, a low-fat diet may reduce the risk of ovarian cancer.

Genetic risk factors

Inherited genetic syndromes are also associated with the development of ovarian cancer. The most common hereditary form of ovarian cancer is associated with the BRCA1, BRCA2, and the mismatch repair genes MLH1, MSH2, MSH6, and PMS2. These genes normally act to prevent the abnormal growth of cells and to help repair DNA damage. When mutated, or altered, these genes can increase the risk of developing cancer. In fact, germline mutations in these genes are present in approximately 15% of ovarian cancer cases.

Recently, germline mutations in a number of other DNA repair genes were detected in ovarian cancer patients and have been associated with an increased risk of the disease. Such genes include BRIP1, NBN, BARD1, PALB2, RAD51C, RAD51D and others in the Fanconi Anemia pathway.

For women with a mutation of the BRCA1 gene the lifetime risk of ovarian cancer is estimated to be 35-70%. For women who harbor a BRCA2 mutation, the risk of ovarian cancer is 10-30%. Women diagnosed with ovarian cancer are now commonly tested for BRCA gene mutations. Those women who harbor a BRCA mutation but have not developed an ovarian cancer usually undergo surveillance monitoring or prophylactic surgery. 

Personal History

  • Have had breast cancer at age 50 or younger

  • Have ever had ovarian cancer

  • Are male and have had breast cancer at any age

  • Are of Ashkenazi Jewish descent and have a personal or family history of breast, ovarian, prostate or pancreatic cancer

Family history

  • Has had two breast cancers in the same person or on the same side of the family

  • Has had someone diagnosed with triple negative breast cancer at any age

  • Has had pancreatic cancer and an HBOC-associated** cancer in the same person or on the same side of the family

  • Has three or more family members with breast cancer on the same side of the family has had a previously identified BRCA1, BRCA2 or other gene mutation in the family