Ovarian Cancer Causes

A number of causes of cancer of the ovaries have been identified, ranging from age and family genetics to prolonged use of hormone replacement therapy (HRT). A woman’s reproductive history may also play a role in determining ovarian cancer risk levels.

Most clinical studies into causes of cancer of the ovaries have examined the most common form of ovarian cancer. Epithelial carcinoma begins on the surface of the ovaries, and is responsible for the majority of malignant tumors. The causes of germ cell and stromal tumors, the two less common forms of ovarian cancer, are slightly different.

Healthy OvariesAge and Incidence Rates

Age is perhaps the greatest risk factor for ovarian cancer. The chance of developing the disease increases just before menopause and continues to rise in postmenopausal women as they age. Half of all cases are diagnosed after the age of 65, and the peak incidence rate occurs between the ages of 70 and 79.


Statistically, Caucasians have a higher risk of ovarian cancer than people of African descent. Approximately nine out of every 100,000 African American women develop the disease. In comparison, 14 out of every 100,000 Caucasian women are diagnosed with ovarian cancer.

Ovarian TumorsEthnically, the highest incidence rate occurs in European women of Jewish ancestry. Incidence rates jump to more than 17 out of every 100,000 women in this ethnic group.

Genetics and Breast Cancer

Genetics play a role in ten percent of ovarian cancer cases. In these cases, the affected women inherit the mutated genes BCRA1 and BCRA2. These genes also increase the risk of developing breast cancer.

Personal and Family History

Genetics are closely tied to family histories of cancer. Women who have a parent or sibling (first-degree relative) with ovarian, endometrial, breast, or colon cancer are at greater risk of developing ovarian tumors.

The risk of developing ovarian cancer increases even more if two first-degree relatives have one of the listed diseases. Having a grandparent, aunt, uncle or cousin (second-degree relative) with one of these cancers also increases personal risk levels, but not as significantly as a first-degree relative.

A personal history of colon, endometrial or breast cancer also raises the risk of ovarian cancer development.

Reproductive History and Oral Contraceptives

The longer a woman ovulates, the greater the risk of ovarian cancer. As a result, women who start to ovulate early in life or those who experience delayed menopause are at higher risk than other women.

Pregnancy appears to reduce the risk. Not becoming pregnant or having one’s first child after age thirty increases the risk. Breastfeeding, even for a short time, appears to provide some protection against ovarian cancer.

The use of oral contraceptives reduces the risk by up to fifty percent in high-risk women, a protective factor that lasts for years after taking the medication.


A high fat diet appears to increase the chances of developing ovarian cancer. The National Cancer Institute recommends a balanced diet high in fruit and vegetables as a possible preventive measure for many forms of cancer. Clinical trials linking ovarian tumors to high lactose and caffeine consumption have produced varying results.

Hormone Replacement Therapy and Estrogen

Hormone replacement therapy has been studied as one of the possible causes of cancer. To date, only one clinical study has produced evidence that hormone replacement therapy increases the chances of ovarian cancer. However, the women studied were on long term HRT with estrogen alone for ten or more years. Combination estrogen and progesterone therapy, however, is not associated with any increase in risk.


Rymer, J., Wilson, R., Ballard, K. (2003, February 8). Making decisions about hormone replacement therapy. British Medical Journal 326, 322-326.