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Ovarian Cancer (cont.)

Ovarian Cancer Causes and Risk Factors

In most ovarian cancer cases, no identifiable cause is present; however, family history does play a role.

  • The lifetime risk for U.S. women of developing ovarian cancer is low.
  • If one first-degree relative -- a mother, sister, or daughter -- has the disease, the risk increases.
  • The risk can climb to 50% if two first-degree relatives have the disease.
  • If a woman has ovarian cancer and her daughter develops ovarian cancer, the daughter will probably develop the cancer at a relatively young age (younger than 60 years).

Ovarian cancer has been linked with three hereditary syndromes.

  • Breast-ovarian cancer syndrome
  • Hereditary nonpolyposis colorectal cancer syndrome
  • Site-specific ovarian cancer syndrome

Breast-ovarian cancer syndrome: A mutation in a gene called BRCA1 has been linked to increased risk of both breast and ovarian cancer.

  • Some women who have this mutation develop ovarian cancer.
  • Another mutation, involving the BRCA2 gene, also increases the risk of ovarian cancer but to a lesser degree.
  • These mutations are hereditary.
  • Clues that may indicate the presence of these mutations include family members who have ovarian cancer or breast cancer (especially those who are diagnosed with these cancers when younger than 50 years), a relative with both breast and ovarian cancer, or a male relative with breast cancer.
  • Development of more precise estimates of cancer risk and better genetic testing for carriers of these genes is taking place.

Hereditary nonpolyposis colorectal cancer (HNPCC) syndrome (Lynch syndrome II): This genetic syndrome has been dubbed "family cancer syndrome" and is associated with colon cancer developing in people younger than 50 years.

  • Other organs that can be involved include the uterus, ovary, breast, stomach, and pancreas.
  • A mutated gene causes this syndrome.
  • Women with this syndrome have a chance of developing ovarian cancer.

Site-specific ovarian cancer syndrome: This is the least common of the three syndromes and experts don't know much about it, yet. This syndrome may be due to mutations of the BRCA1 gene.

Other factors that increase ovarian cancer risk include the following:

  • Age greater than 50 years
  • No pregnancies
  • Use of fertility drugs: Some studies have shown that the use of fertility drugs increases the risk of ovarian cancer, but study results have not been consistent.
  • Ashkenazi Jewish heritage
  • European (white) heritage: White women are much more likely to have ovarian cancer than African American women.
  • Asbestos exposure
  • Repeated exposure of the genitals to talc
  • Irradiation of the pelvic area
  • Some viruses, especially the virus that causes mumps

Some findings suggest that estrogen may promote ovarian cancer in women who have been through menopause. For years, the cancer risks involved with using hormone replacement therapy divided the medical community. Research findings in 2002 and early 2003 showed that hormone replacement therapy does not provide many of the benefits it was believed to have, and it increases the risk of heart disease. Experts no longer routinely recommend long-term hormone replacement therapy for most women, though the issue can be considered on a case by case basis.

Some factors decrease ovarian cancer risk.

  • Any factor that inhibits ovulation (release of an egg from the ovary) seems to protect against development of ovarian cancer. This may be because ovulation disrupts the epithelial layer of the ovary. As cells divide to repair the damage, uncontrolled division and malignant changes may occur.
  • Term pregnancy (lasting the full nine months) significantly reduces the risk of ovarian cancer. As the number of pregnancies increases, the risk of ovarian cancer decreases.
  • Use of oral contraceptives (birth control pills) reduces the risk of ovarian cancer.
  • Breastfeeding lowers risk of ovarian cancer, and the risk decreases with increasing duration of breastfeeding.
  • Removal of the ovaries before cancer reduces the risk of cancer arising in the ovaries to zero. However, cases of a closely related condition called primary peritoneal carcinoma due to embryonic remnants of ovarian formation can still occur. This may be a consideration in women with inherited cancer risks. Experts should base this decision on genetic testing and counseling.
  • Having the woman's "tubes tied" (tubal ligation) to prevent pregnancy.
  • Having a hysterectomy lowers the risk of ovarian cancer.
Medically Reviewed by a Doctor on 9/9/2015
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