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What is ovarian cancer?
Ovarian cancer is the uncontrolled growth of cells within a woman’s ovary. The ovaries are reproductive glands that are located on either side of the uterus in the lower abdomen.
The ovaries have two main functions:
- To produce the hormones estrogen and progesterone that are responsible for the development of secondary sexual features (e.g., breast growth, pubic hair) and regulation of the reproductive cycle
- To develop and release an egg into the fallopian tube once a month during childbearing years
Ovarian cancer is the fifth most common cause of cancer death in women. According to the American Cancer Society (ACS), the life-time risk of developing ovarian cancer is about 1 in 78. ACS estimates that about 22,500 new cases are diagnosed each year in the United States and nearly 14,000 women die of it. Invasive ovarian cancer is a more common cause of death than the more prevalent and easily detected cervical cancer and uterine cancer. Ovarian cancer is more difficult to detect, so it is often diagnosed at later stages, when it is more difficult to treat.
Ovarian tumors can be non-cancerous (benign) or cancerous (malignant). It is not usually possible to tell whether a tumor is cancerous until the ovary has been biopsied or removed or the cancer has spread to other parts of the body. Ovarian tumors fall into three categories:
- Epithelial tumors (majority of ovarian tumors) – begin in the epithelial cells covering the outside of the ovaries
- Germ cell tumors (less than 2% of all ovarian tumors) – occur in the egg-producing cells and are more often seen in younger women
- Stromal tumors (about 1% of all ovarian tumors) – derive from connective tissues of the ovary that produce estrogen and progesterone
While benign tumors do not spread (metastasize), cancerous (malignant) ovarian tumors will spread if left undiagnosed and untreated – first throughout the ovary, then to the uterus, bladder, rectum, and the lining of the abdomen. Eventually, cancerous cells will reach the lymph nodes and spread throughout the body.
About Ovarian Cancer
The main risk factor for ovarian cancer is a family history of ovarian cancer on either your mother’s or father’s side of the family. According to the American Cancer Society, about 5% to 10% of ovarian cancers develop from an inherited (genetic) risk. Some examples include:
- Hereditary breast and ovarian cancer syndrome—inherited harmful (pathogenic) genetic variants in the BRCA1 and BRCA2 genes are associated with a significantly increased lifetime risk of developing ovarian cancer. For women with BRCA1 pathogenic variants, the risk is estimated to be 35-70% and for women with BRCA2 pathogenic variants it is 10-30%. Women without these pathogenic variants have a lifetime risk of about 2%.
- Hereditary nonpolyposis colon cancer (Lynch syndrome)—inherited pathogenic variants in several genes (MLH1, MLH3, MSH2, MSH6, TGFBR2, PMS1, PMS2) are associated mainly with an increased risk of colon cancer, but women may also have a higher risk of ovarian cancer (a lifetime risk of about 10%).
Other risk factors include:
- Age—about half the ovarian cancers are found in women 63 years of age or older. Most ovarian cancers develop after menopause.
- Race—ovarian cancers are more common in Caucasian women than in African American women.
- Personal history of breast cancer
- Not having children or having children after age 35
- Being overweight or obese
- Taking hormone replacement therapy
- Having fertility treatment
Factors that may be associated with decreased risk include taking oral contraceptives, having children when younger than age 26, and breastfeeding.
Signs and Symptoms
The primary reasons ovarian cancers go undetected are that there is no reliable screening test and the symptoms are often not noticeable and fairly non-specific, meaning there are many non-cancerous conditions that can cause similar symptoms and often be difficult to tell apart. Some examples of signs and symptoms include:
- Abdominal discomfort, pressure, bloating, or swelling
- Strong, frequent urge to urinate and/or change in bowel habits
- Pelvic pain or discomfort
- Loss of appetite, indigestion, gas or nausea
It is important to have regular checkups and to consult with a healthcare practitioner if signs and symptoms develop.
Currently, there is no specific screening test for ovarian cancer. The U.S. Preventive Services Task Force (USPSTF) recommends against screening women for ovarian cancer. This recommendation applies to asymptomatic women (the general population) but not to women at a high risk of developing ovarian cancer, such as those with a known harmful (pathogenic) genetic variant (e.g., BRCA1/2 variant). Women with increased risk may be monitored with a combination of transvaginal ultrasounds and blood tests for the tumor marker CA-125.
The need for a reliable method for early detection of ovarian cancer among asymptomatic women continues to drive ongoing research. Molecular (gene) tests and multimarker approaches are being explored to improve early detection of ovarian cancers. In the meantime, regular physicals, pelvic exams, and an awareness of family history and symptoms are important.
Tests for increased risk
Women with a strong family history or ethnicity associated with ovarian cancer may receive genetic counseling and have genetic testing done. A common example is BRCA1 and BRCA2 testing. These tests detect harmful genetic variants that are known to increase the risk of breast and ovarian cancer. Only about 0.2% of the U.S. population carries a harmful BRCA1 or BRCA2 variant. Because of this, genetic testing is not recommended for the general population.
If an abnormality is found, such as a growth detected during an ultrasound, and ovarian cancer is suspected, a biopsy is typically required to confirm the diagnosis. A sample of the growth is removed during surgery and sent to the laboratory. A pathologist uses a microscope to examine the sample and determine whether cancer is present.
- CA-125 (Cancer antigen 125) – this is a tumor marker primarily used to monitor therapy during treatment for ovarian cancer. CA-125 is also used to detect whether cancer has come back after treatment is complete. A series of CA-125 tests that shows rising or falling levels is often more useful than a single result.
- HE4 (Human epididymis protein 4) – a relatively new tumor marker that shows promise. It may be used along with CA-125 to monitor women who have been treated for epithelial ovarian cancer. In order for HE4 to be useful as a tumor marker, it must be elevated prior to treatment.
Other tests may be ordered to help monitor different types of ovarian tumors. The tests may help determine whether treatment (e.g., surgery, chemotherapy) is successful and whether cancer has returned. Some examples include:
- Epithelial tumors
- Carcinoembryonic antigen (CEA) – less specific and sensitive than CA-125; not recommended for routine use
- Germ cell tumors
- Stromal tumors
Imaging tests that may be used to evaluate the ovaries include:
- Ultrasound (pelvic and/or transvaginal) – uses sound waves to create a picture of the uterus and ovaries; it can help determine whether an ovarian growth is likely to be a cancer or a fluid-filled cyst.
- CT scan (computerized tomography) or X-rays may be used to see if the cancer has spread.
- MRI (magnetic resonance imaging) may be used to see if the cancer has spread.
Staging and Treatment
If cancer is found, surgery to remove the cancerous tissue is performed (oophorectomy). Additional tissues may be removed to determine the stage of the disease, most commonly the fallopian tubes (salpingectomy). Ovarian cancer staging is complex but generally, one of four stages of cancer is identified, depending on the spread of the tumor. They are:
- Stage 1 – this stage includes cancer present in one or both ovaries or fallopian tubes as well as cancer that has spread to the outside surface of these organs and/or in pelvic or abdominal fluid. However, the cancer has not spread to nearby organs or lymph nodes or distant sites (about 20% of ovarian cancers diagnosed with best prognostic outcomes).
- Stage 2 – this stage includes cancer that has spread to nearby pelvic organs such as the uterus, bladder, rectum and/or lower colon but not to nearby lymph nodes or distant organs.
- Stage 3 – this stage includes cancer that has spread to the abdomen lining or surrounding lymph nodes.
- Stage 4 – cancer has spread to other organs beyond the abdomen.
Treatment usually depends on the type and stage of the cancer. The main treatment is surgery and may also include chemotherapy, hormone therapy, targeted therapy, and/or sometimes radiation treatments.
Ovarian cancer treatment is constantly evolving. New drugs, immunotherapies, and bone marrow transplants are being studied for their effectiveness. A woman’s healthcare provider and/or cancer team can help determine the treatment course that is right for her. For more information about treatment, see the links in Related Content.
Sources Used in Current Review
Current review performed by Mutasim Elfahal, PhD, DABCC, Lahey Hospital & Medical Center, Burlington, MA and the LTO Editorial Review Board.
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