Ovarian cancer - Gale Encyclopedia of Medicine

Definition

Ovarian cancer is a disease in which the cells in the ovaries become abnormal and start to grow uncontrollably, forming tumors. Ninety percent of all ovarian cancers develop in the cells that line the surface of the ovaries and are called "epithelial cell tumors."

Description

The ovaries are a pair of almond-shaped organs that lie in the pelvis on either side of the uterus. The fallopian tubes connect the ovaries to the uterus. The ovaries produce and release an egg each month during the menstrual cycle. In addition, they also produce the female hormones estrogen and progesterone, which regulate and maintain the secondary female sexual characteristics.

Ovarian cancer is the fifth most common cancer among women in the United States. It accounts for 4% of all cancers in women. However, the death rate due to this cancer is higher than that of any other cancer among women. The American Cancer Society estimates that in 1998, at least 26,000 new cases will be diagnosed in the United States, and there will be at least 14,500 deaths due to ovarian cancer.

Ovarian cancer can develop at any age, but more than half the cases are among women who are 65 years or older. The incidence of the disease is higher among white women. Only 50% of the women who are diagnosed with ovarian cancer will survive five years after initial diagnosis. This is because at the time of initial diagnosis, the cancer is usually in an advanced stage. It is difficult to diagnose ovarian cancer early, because often there are no warning symptoms and the disease grows relatively quickly. In addition, the ovaries are situated deep in the pelvis and, therefore, small tumors cannot be detected easily during a routine physical examination.

Causes & symptoms

The actual cause of ovarian cancer is not known, but several factors are known to increase one's chances of developing the disease. These are called risk factors.

Age may be considered a risk factor for ovarian cancer, because the incidence of the disease increases with age. Half of all cases are diagnosed after age 65. Race may be another risk factor for the disease, since the incidence of the disease is noted to be the highest among white women and lowest among blacks. A high-fat diet may have something to do with an increased incidence of ovarian cancer, because when Asian women move to the more affluent western countries and adopt a diet that is rich in fat, the incidence of ovarian cancer among them rises.

A family history of ovarian cancer puts a woman at an increased risk for developing the disease. Women who have even one close relative with the disease increase their risk threefold. In addition, if a woman has had breast cancer, she is at an increased risk for ovarian cancer.

Starting to menstruate at a very early age (before age 12) and late menopause seems to put women at a higher risk for ovarian cancer. It is believed that the longer a woman ovulates, the higher is her risk of ovarian cancer (some researchers pin the blame on exposure to estrogen during the monthly cycles). Since ovulation occurs only during the childbearing years, the longer she menstruates, the greater is the risk. Pregnancy gives a break from ovulation and exposure to estrogen for nine months. Hence, multiple pregnancies actually appear to reduce the risk of ovarian cancer. Similarly, since oral contraceptives suppress ovulation and reduce exposure to estrogen, women who take birth control pills have a lower incidence of the disease. One study has shown that prolonged use of certain fertility drugs, such as clomiphene citrate, may increase a woman's risk of developing ovarian tumors.

There have been some studies that have suggested that the use of talcum powder in the genital area may double one's risk of getting the cancer. The incidence of ovarian cancer is higher than normal among female workers exposed to asbestos. Since talc contains particles of asbestos, some researchers believe that is what accounts for the increased risk.

Ovarian cancer has no specific signs or symptoms in the early stages of the disease. There may be some vague, non-specific symptoms, which are often ignored. However, if any of the symptoms persist, it is essential to have them evaluated by a doctor immediately. Only a physician can assess whether the symptoms are an indication of early ovarian cancer. The patient may experience the following symptoms:

• Pain or swelling in the abdomen
• Bloating, and general feeling of abdominal discomfort
• Constipation, nausea or vomiting
• Loss of appetite, fatigue
• Unexplained weight gain (generally due to an accumulation of fluid in the abdomen)
• Vaginal bleeding in post-menopausal women.

Diagnosis

If ovarian cancer is suspected, the physician typically begins the diagnosis by taking a complete medical history to assess all the risk factors. A thorough pelvic examination is conducted. Blood tests to determine the level of a particular blood protein, CA125, may be ordered. This protein is usually elevated when a woman has ovarian cancer. However, it is not a definitive test because the levels may also rise in other gynecologic conditions, such as endometriosis and ectopic pregnancies. Ultrasound may be used to check the size of the ovaries.

In order to determine if the tumor is benign or cancerous, surgery is necessary. If the tumor appears to be small from the imaging tests, then a procedure known as laparoscopy may be used. A tiny incision is made in the abdomen and a slender, hollow, lighted instrument is inserted through it. This enables the doctor to view the ovary more closely and to obtain a piece of tissue for microscopic examination. If the tumor appears large, a laparotomy is performed under general anesthesia. This procedure combines both diagnosis and treatment for ovarian cancer, because the tumor is often completely removed during the procedure. A piece of the tissue that is removed will be microscopically examined to determine whether the tumor was benign or malignant. Surgery confirms the diagnosis, but ovarian cancer is often strongly suspected prior to surgery based on symptoms and ultrasound. The goal of surgery is to completely remove the cancer, but often this is not possible.

Standard imaging techniques such as computed tomography scans (CT scans) and magnetic resonance imaging (MRI) may be used to determine if the disease has spread to other parts of the body.

Treatment

The cornerstone of treatment for ovarian cancer is surgery. It is aimed at removing as much of the cancer as possible. Chemotherapy, which involves the use of anticancer drugs to kill the cancer cells, is usually administered after the surgery to destroy any remaining cancer. Radiation therapy is not routinely used for ovarian cancer.

The type of surgery depends on the extent of spread of the disease. In most procedures, the ovaries, uterus, and fallopian tubes are completely removed. In rare cases, if the cancer is not very aggressive and the woman is young and has not had children, a more conservative approach may be adopted. Only one ovary may be removed, and, if possible, the fallopian tubes and the uterus may be left intact.

Occasionally, in addition to the female reproductive organs, the appendix may also be removed. The liver and the intestine will be examined for signs of cancer and may be biopsied. Ovarian cancer spreads contiguously, which means that it moves to the organs that are next to it. The intestines, the diaphragm (which separates the abdominal cavity from the chest cavity), and the omentum (a sheet-like tissue that connects parts of the abdominal cavity)--indeed, the entire surface of the abdominal cavity--may be studded with disease. In these cases, extensive surgery may be needed to remove as much as possible.

Prognosis

Most often ovarian cancer is not diagnosed until it is in an advanced stage, making it the most deadly of all the female reproductive cancers. More than 50% of the women who are diagnosed with the disease die within five years. If ovarian cancer is diagnosed while it is still localized to the ovary, more than 90% of the patients will survive five years or more. However, only 24% of all cancers are found at this early stage.

Prevention

Since there is no known cause for ovarian cancer, it is not possible to prevent the disease. Nevertheless, there are ways to reduce one's risks of developing the disease.

Currently genetic tests are available which can help to determine whether a woman who has a family history of breast, endometrial, or ovarian cancer has inherited the mutated gene that predisposes her to these cancers. (This mutation affects only a few women, however.) If the woman tests positive for the mutation, then she can opt to have her ovaries removed (oophorectomy). However, this means that the woman cannot have any more children. Even without testing for the mutated gene, some women with strong family histories of ovarian cancer may consider having her ovaries removed as a preventative measure (prophylactic oophorectomy).

Procedures such as tubal ligation (in which the fallopian tubes are blocked or cut off) and hysterectomy (in which the uterus is removed) appear to reduce the risk of ovarian cancer. If a woman undergoes one of the procedures, she can also consider having her ovaries removed to eliminate the risk of ovarian cancer. Having one or more children, preferably having the first before age 30, and breastfeeding may decrease one's risk of developing the disease.

There are no simple tests or screening procedures to detect ovarian cancer in its early stages. High-risk women are therefore advised to undergo periodic screening with the transvaginal ultrasound or a blood test for CA125 protein.

The American Cancer Society recommends annual pelvic examinations for all women after age 40, in order to increase the chances of early detection of ovarian cancer.

Key Terms

Computed tomography (CT) scan

A series of x rays that are put together by a computer in order to form detailed pictures of areas inside the body.

Ectopic pregnancy

A pregnancy that results when the fused egg and sperm implants itself in the fallopian tubes (or other places in the body) instead of the womb.

Endometriosis

A condition that causes an inflammation of the inner lining of the uterus and sometimes results in heavy vaginal bleeding.

Laparoscopy

A diagnostic procedure in which a small incision is made in the abdomen and a slender, hollow, lighted instrument is passed through it. The doctor can view the ovaries more closely through the laparoscope, and if necessary, obtain tissue samples for biopsy.

Laparotomy

An operation in which the abdominal cavity is opened up.

Magnetic resonance imaging (MRI)

A medical procedure used for diagnostic purposes in which pictures of areas inside the body can be created using a magnet linked to a computer.

Transvaginal ultrasound

A procedure in which a device is inserted through the vagina and sound waves are bounced off the ovary walls. The echoes created by the reflected sound waves can be used to image the ovaries.

Further Reading

For Your Information

Books

• Berkow, Robert, et al., eds. Merck Manual of Diagnosis and Therapy, 16th ed. Merck Research Laboratories, 1992.
• Dollinger, Malin. Everyone's Guide to Cancer Therapy. Somerville House Books Limited, 1994.
• Morra, Marion E. Choices. Avon Books, 1994.
• Murphy, Gerald P. Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment and Recovery. American Cancer Society, 1997.

  Organizations

• American Cancer Society. 1599 Clifton Road, N.E. Atlanta, Georgia 30329. (800) 227-2345. http://www.cancer.org.
• Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623. http://www.cancerresearch.org.
• Gilda Radner Familial Ovarian Cancer Registry. Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263. (800) 682-7426.
• Gynecologic Cancer Foundation. 401 North Michigan Avenue, Chicago, IL 60611. (800) 444-4441.
• National Cancer Institute. 9000 Rockville Pike, Building 31, room 10A16, Bethesda, Maryland, 20892. (800) 422-6237. http://wwwicic.nci.nih.gov.
• Oncolink. University of Pennsylvania Cancer Center. http://cancer.med.upenn.edu.

Gale Encyclopedia of Medicine. Gale Research, 1999.