Ovarian Cancer

Introduction to Ovarian Cancer

Ovarian cancer is the 5th most common cancer in women, with 1 in 70 women in the United States developing it by age 70. Ovarian cancer occurs most frequently in women over age 60. Five percent of all cancer deaths among women in the United States are caused by ovarian cancer. However, there are marked differences in survival among patients with ovarian cancer, depending upon the age of the individual and the cancer stage at the time of diagnosis, in addition to the cancer tissue type.

What is Ovarian Cancer?

Ovarian cancer is a disease caused by the rapid growth and division of cells within one or both ovaries. The ovaries are the reproductive glands that make the ova (eggs) and the female sex hormones, such as estrogen and progesterone. Ovarian cancer is a general term that includes cancer of 30 different tissue types falling into 3 categories:

 

  1. Epithelial cancers, which arise from cells lining or covering the ovaries: These are the most common ovarian cancers and account for 85 to 90% of ovarian cancer cases.

     

  2. Germ cell cancers, which start from germ cells within the ovaries: These are the cells that are destined to form eggs and these cancers account for 10 to 15% of all ovarian cancer cases.

     

  3. Sex cord, or stromal cell cancers: These begin in the cells that hold the ovaries together and produce female hormones such as estrogen and progesterone. This type of ovarian cancer is very rare.

What Are Risk Factors for Ovarian Cancer?

Both non-genetic and genetic risk factors have been determined for ovarian cancer.

Non-genetic risk factors are:

  • Age: The majority of ovarian epithelial cancers occur after menopause

     

  • Family history of ovarian cancer: This is the most important factor to consider when estimating the risk for ovarian cancer. Studies have suggested that a woman has up to a 50% risk of developing ovarian cancer if two or more of her 1st or 2nd degree relatives have had ovarian cancer.

     

  • Hormonal history: It has been suggested that the more menstrual cycles a woman has in her lifetime, the higher her risk for developing ovarian cancer. A somewhat increased risk for ovarian cancer is seen in women who:
    – Began menstruating before age 12
    – Went through menopause after age 50
    – Are nulliparous (never gave birth)
    – Have had a first child after the age of 30

It has also been suggested that multiple pregnancies, long-term oral contraceptive use, or breast-feeding have an increasingly protective effect, perhaps related to their suppression of ovulation.
See The Role of Estrogen in Breast and Ovarian Cancer for more information.

 

  • Other potential risk factors include obesity and a high fat diet. However, researchers have yet to prove a direct connection between any of these last potential risk factors and an increased risk for ovarian cancer.

    Genetic risk factors include:

    • Mutations in specific oncogenes: Oncogenes are genes that control cellular growth and, when mutated, they allow cells to divide and reproduce out of control. Studies have suggested that mutations acquired in the HER2 and p53 oncogenes are associated with the development of ovarian cancer. This remains unproven.

       

    • Mutations in predispositional tumor suppressor genes BRCA1 and BRCA2: These tumor suppressor genes have also been associated with ovarian cancer. See BRCA1, BRCA2, and Possibilities for BRCA3 for more in-depth information.

       

    • Other genes not yet discovered: It is assumed that there are also other genes not yet known that are related to familial forms of breast and ovarian cancer.

    What Can I do to Monitor My Risks for Ovarian Cancer?

    Unfortunately no effective screening exists that decreases the mortality and morbidity of ovarian cancer. Therefore, no surveillance is recommended for the general population. For women at a high risk to develop ovarian cancer, suggested surveillance is:

     

  • Annual or semi-annual pelvic examinations beginning at age 25 to 35

    Experimental protocols that may be helpful in women at high risk but that are currently unproven include:

     

  • Transvaginal ultrasound with CA-125 levels

     

  • Proteomic marker profile

    What Happens When Ovarian Cancer Has Been Diagnosed?

    Once an ovarian mass or tumor has been found, surgery is almost always done to remove as much of the tumor mass as possible and then to analyze and stage the tumor. If ovarian cancer is diagnosed from the results of this analysis, surgery is generally done to remove the uterus, ovaries, and fallopian tubes. Fatty tissue covering the bowels may also be removed to check for metastasis. Women with epithelial ovarian cancers at high risk of recurrence or in who cancer remains after the surgery receive chemotherapy after surgery (or occasionally before surgery). Prophylactic removal of the ovaries (oophorectomy) may also be considered in women who are at a high risk for developing ovarian cancer but who have not yet developed it.

    __________________________________________________________________

    Reviewed by Wendy Rubinstein, MD, PhD, Center for Medical Genetics, Evanston Northwestern Healthcare 8/03.