Ovarian cancer is the most common cause of cancer death due to gynecologic tumors in the United States. More than 200,000 women in the world are estimated to develop ovarian cancer every year and about 100,000 die from the disease. The lifetime risk of a woman developing epithelial ovarian cancer is 1 in 70. While believed to arise from the surface of the ovaries, many of these actually originate in the fallopian tubes.
The precise cause of ovarian cancer is unknown. However, several risk and contributing factors (including both reproductive and genetic factors) have been identified.
Risk Factors for Ovarian Cancer
1. Live births or pregnancies that are of longer duration, regardless of outcome, lower one’s risk of ovarian cancer. The risk of the most common type of ovarian cancer is increased in women who have not had children and possibly those with early menarche or late menopause. Women who have been pregnant have a 50% decreased risk for developing ovarian cancer compared with women who have never had a child. Multiple pregnancies offer an increasingly protective effect.
2. Oral contraceptive use decreases the risk of ovarian cancer significantly.
These factors support the idea that risk for ovarian cancer is related to ovulation.
Thus, the probability of ovarian cancer may be related to the number of ovulatory cycles, and conditions that suppress the ovulatory cycle (such as birth control pills) may play a protective role. However, fertility drugs to cause ovulation have not been shown to increase the risk of ovarian cancer
1. Family history plays an important role in the risk of developing ovarian cancer. The lifetime risk for developing ovarian cancer is 1.6% in the general population. This compares with a 4-5% risk when 1 first-degree family member is affected, rising to 7% when 2 relatives are affected. From 5-10% of cases of ovarian cancer occur in an individual with a family history of the disease.
Hereditary ovarian cancer occurs at a younger age (approximately 10 years younger) than nonhereditary epithelial ovarian cancer, but the prognosis may be somewhat better.
2. Evidence from the Cancer Genome Atlas Network showed that some types of ovarian tumors and breast tumors shared a number of genetic characteristics, such as the types and frequencies of gene mutations, suggesting that ovarian and breast cancer may have a related cause and potentially similar responsiveness to some of the same therapies.
At least two syndromes of hereditary ovarian cancer are clearly identified, involving either (1) disorders of the genes associated with breast cancer, BRCA1 and BRCA2, or (2) more rarely, genes within the Lynch II syndrome complex.
Breast/ovarian cancer syndrome is associated with early onset of breast or ovarian cancer. Inheritance can come from either parent.
Most cases are related to the BRCA1 gene mutation. BRCA1 is a tumor suppressor gene that inhibits cell growth when functioning properly meaning that a mutation of it causes it to not function properly.
Approximately 1 person in 4000 in the general population carries a mutation of BRCA1. Some populations have a much higher rate of BRCA1 and BRCA2 mutations, especially Ashkenazi Jews.