February 19, 2015
Risk Factors and Ovarian Cancer
Written by Board Member and Medical Advisor Sarah Adams, MD
Ovarian cancer is characterized by presentation at late stages, usually when women have tumors throughout the abdomen and pelvis. This is due in part to the lack of effective screening strategies, but may also be due to the early spread of cancer cells in the abdominal cavity and to rapid tumor growth. It has long been hoped that a better understanding of the causes of ovarian cancer and factors that promote tumor development would lead to earlier detection and better outcomes for women with this disease.
The best understood risk factor for ovarian cancer development is a family history of breast or ovarian cancer, and specifically the presence of mutations in the BRCA1 or BRCA2 genes. Women who inherit a dysfunctional copy of BRCA1 or BRCA2 are more likely to develop ovarian cancer– with a lifetime risk as high as 40%. Fortunately women who are found to have a BRCA gene mutation can significantly reduce their risk either by having their ovaries removed if they have completed child-bearing, or by taking birth control pills. Currently genetic testing is recommended for all women diagnosed with ovarian cancer, and genetic counseling to assess cancer risk is recommended for women with a family member who has had breast or ovarian cancer. Importantly, additional genes that are often dysfunctional in ovarian cancers have recently been identified. As the impact of these mutations on cancer risk is evaluated, additional women with inherited susceptibility can be identified and offered risk-reduction options.
Other factors that have been associated with ovarian cancer development are less well understood. An early theory suggesting a link with the use of talc powder has recently been disproven in a large study of over 60,000 women (Houghton SC et al, J Natl Cancer Inst 2014). A more established factor that modulates risk of ovarian cancer is a woman’s reproductive history. Women who have never had children, or who have early onset of menstrual periods or late menopause have been shown to have a higher rate of ovarian cancer development. This increased risk of cancer is associated with increases in the number of ovulatory cycles a woman has in her lifetime – each ovulation event induces local inflammation and requires tissue repair, which could result in cells acquiring cancer-causing mutations. Conversely, pregnancy, breastfeeding, and the use of oral contraceptive pills, which interrupt ovulation cycles, all reduce the risk of ovarian cancer.
Interestingly, recent studies suggest that a significant proportion of ovarian cancers actually originate in the fallopian tubes, with early cancers seeding the ovaries before spreading beyond the pelvis. This data derives from careful examination of the ovaries and fallopian tubes removed from women with BRCA gene mutations for cancer risk reduction. This shift in the understanding of the origin of ovarian cancer has led to a new interest in the impact of ovulation on local conditions that could affect both the ovarian surface cells and the nearby fallopian tube. As a result, physicians have begun to evaluate whether removing just the fallopian tubes, and not the ovaries, in young women would provide protection from cancer development without rendering women prematurely menopausal. Ongoing studies are expected to clarify the risks and benefits of this approach, which will allow women and clinicians to make decisions that will best prevent ovarian cancer development.
Women should talk with their health care providers to determine whether genetic counseling or risk reduction procedures are indicated for them. Additional information about ovarian cancer risk and genetic testing is available at the following sites:
National Cancer Institute: Cancer Genetics Services Directory www.cancer.gov/cancertopics/genetics/directory
Dr. Sarah Adams is the Victor and Ruby Hansen Surface Professor in Ovarian Cancer Research and the Assistant Professor, Gynecologic Oncology at the University of New Mexico Cancer Center