Deepti Babu. The Gale Encyclopedia of Genetic Disorders. Ed. Brigham Narins. 2nd edition. Volume 2. Detroit: Gale, 2005.
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.”
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 a woman’s menstrual cycle. In addition, they also produce the female hormones estrogen and progesterone, which regulate and maintain the proper growth and development of 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, ovarian cancer is very difficult to discover in the early stages. This is often because there are no obvious warning signs, and the disease can grow relatively quickly. In addition, the ovaries are situated deep in the abdomen and small tumors may not be detected easily during a routine physical examination. Because of this, the death rate due to ovarian cancer is higher than that of any other cancer among women, since it may only be detected at advanced stages.
Ovarian cancer can develop at any age, but more than half the diagnoses are among women who are 60 years or older. The vast majority of people with ovarian cancer have no family history of the disease. However, for about 5-10% of individuals, there may be a very strong family history of ovarian cancer or other cancers, such as breast cancer. In these cases, a specific genetic alteration may be in the family, causing a predisposition to ovarian cancer and other associated cancers.
Cells in ovarian tissue normally divide and grow, according to controls and instructions by various genes. If these genes have changes within them, the instructions for cellular growth and division may go awry. Abnormal, uncontrolled cell growth may occur, causing ovarian cancer. Therefore, all ovarian cancers are genetic because they all result from changes within genes. The difference is that most ovarian cancers are caused by sporadic changes within the genes, and only a minority are caused by inherited genetic alterations. Most ovarian cancers occur later in life after years of exposure to various environmental factors (such as the body’s own hormones, asbestos exposure, or smoking) that can cause sporadic genetic alterations.
A small proportion of ovarian cancer is caused by inherited genetic alterations. A genetic alteration causing a predisposition solely to ovarian cancer has not yet been identified. However, in 1994 a breast and ovarian cancer susceptibility gene, known as BRCA1 (location 17q21), was identified. The discovery of BRCA2 (location 13q12) followed shortly in 1995. Women with alterations in these genes have an increased risk for breast and ovarian cancer, and men have an increased risk for prostate cancer. Men with a BRCA2 alteration have an increased risk for breast cancer. Slightly increased risks for colon and pancreatic cancers (in men and women) are also associated with BRCA2 alterations.
BRCA1 and BRCA2 alterations are inherited in an autosomal dominant manner; an individual who has one copy of a BRCA alteration has a 50% chance to pass it on to each of his or her children, regardless of that child’s gender. Nearly all individuals with BRCA alterations have a family history of the alteration, usually a parent with it. In turn, they also may have a very strong family history of breast, ovarian, prostate, colon, and/or pancreatic cancers. Aside from BRCA1 and BRCA2, there likely are other cancer susceptibility genes that are still unknown.
In addition to BRCA1 and BRCA2, ovarian cancer may be present in rare genetic cancer syndromes. In these instances, an individual may have other health problems (unrelated to cancer) and a family history of a wide variety of cancers and symptoms. As an example, Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is a syndrome that often involves cancers of the colon, uterus, ovaries, and stomach. HNPCC is due to changes in several genes including hMLH1, hMSH2, hMSH6, and hPMS2. These genes are unrelated to BRCA1 and BRCA2.
On average, a North American woman faces a lifetime risk of approximately 2% to develop ovarian cancer. The incidence of ovarian cancer is higher among Caucasian women. The American Cancer Society stated that in the year 2000 about 23,100 new cases of ovarian cancer were diagnosed in the United States, and 14,000 women died from the disease. Specific BRCA alterations are common in certain ethnic groups, which may make hereditary ovarian cancer more common in these populations. Certain BRCA alterations are more common in the Ashkenazi (Eastern European) Jewish, Icelander, Dutch, French Canadian, and West African populations.
Signs and Symptoms
Ovarian cancer has no specific signs or symptoms in the early stages of the disease. However, one may experience some of the following:
- Pain or swelling in the abdominal area
- Bloating and general feeling of abdominal discomfort
- Constipation, nausea or vomiting
- Loss of appetite, tiredness
- Unexplained weight gain (generally due to fluid building up from the cancer in the abdomen)
- Vaginal bleeding in women who have already gone through menopause
Only a physician can assess whether or not the symptoms are an indication of early ovarian cancer. This is why it is important for a physician to be informed right away if any of the above symptoms are present.
A family history of ovarian cancer puts a woman at an increased risk for developing the disease. In addition, if a woman has had, or has a family history of breast cancer she may be at an increased risk for ovarian cancer. Signs of a possible BRCA1 or BRCA2 alteration in a family, signifying hereditary breast or ovarian cancer, include:
- Several relatives with cancer
- A large number of relatives with cancer versus unaffected relatives
- Close genetic relationships between people with cancer, such as parent-child, sibling-sibling
- Earlier ages of cancer onset, such as before ages 45-50
- An individual with both breast and ovarian cancer
- An individual with bilateral or multi-focal breast cancer
- The presence of ovarian, prostate, colon, or pancreatic cancers in the same family
- Case(s) of breast cancer in men
Suspicion of a BRCA alteration may be raised if someone has the above features in their family and they are of a particular ethnic group, such as Ashkenazi Jewish. This is because specific BRCA1 and BRCA2 alterations are known to be more common in this group of individuals.
If a woman has symptoms of ovarian cancer, a pelvic examination is usually conducted to feel the ovaries to see if they have enlarged, indicative of a tumor. Blood tests to determine the level of a protein, known as carbohydrate antigen 125 (CA-125), may be done. CA-125 blood levels can be high when a woman has ovarian cancer. Additionally, a pelvic or transvaginal ultrasound (with color Doppler imaging) may be used to get several views of the ovaries, carefully checking their shape and structure. A CT scan may be helpful if the ultrasound is technically unsatisfactory for accurate interpretation.
A biopsy and surgery is necessary in order to determine the type of tumor, as not all tumors are cancerous. If the tumor appears to be small, 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 biopsy. If the ovary has suspicious findings on laparoscopy and biopsy, a laparotomy (open surgery performed under general anesthesia) and removal of that ovary is usually performed. Large masses are investigated by open surgery.
Standard imaging techniques such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) may be used to determine if the disease has metastasized (spread) to other parts of the body.
There is DNA-based genetic testing to identify a BRCA1 or BRCA2 alteration in an individual. In the United States, Myriad Laboratories in Utah is the only place to offer this costly testing (as of 2001, it was about $2,700 for initial analysis). A blood sample is used, and both BRCA genes are studied for alterations. There is also targeted testing for people in high-risk ethnic groups (such as Ashkenazi Jewish) in which only the common BRCA alterations can be tested. Even with current technology, only certain regions of the BRCA genes can be studied, which leaves some alterations unable to be found.
For women without cancer who test positive for a BRCA alteration, this now places them at a significantly increased risk to develop the associated cancers. A woman’s risks associated with a BRCA1 alteration are: 40-60% for ovarian cancer by age 70 and 3-85% for breast cancer by age 70. A woman’s risks with a BRCA2 alteration are: 16-27% for ovarian cancer by age 70 and 4-86% for breast cancer by age 70.
For women with ovarian cancer who are found to have a BRCA alteration, this now places them at an increased risk to develop breast cancer. For some women, this may be a new risk they were not aware of before the testing, particularly if they have no family history of breast cancer.
For all women with a BRCA2 alteration, there may be a slightly increased risk for colon and pancreatic cancers. Additionally, because the testing process and test results are quite complex (and may have strong emotional consequences) everyone should receive proper genetic counseling before pursuing any BRCA1 and BRCA2 testing. Prenatal BRCA testing is available, but is rarely performed unless accompanied by extensive genetic and psychological counseling.
Treatment and Management
As with many other cancers, treatment is determined by the exact size and type of ovarian cancer, so it is often unique to an individual. However, the cornerstone of treatment for ovarian cancer is surgery. This may require a laparotomy procedure in order to remove as much cancerous tissue as possible. Other organs, such as the uterus and fallopian tubes, may also be removed (especially if the cancer has spread there). Chemotherapy, the use of strong chemicals to kill cancer cells, is usually done following surgery. The purpose is to destroy any remaining cancer cells. Radiation therapy (using radioactive waves to kill cancer cells) is not typically used for ovarian cancer because it is not as effective as other treatments.
Screening recommendations for women at high risk to develop ovarian cancer (such as those with a strong family history of the disease) may include:
- Pelvic examination every six months or yearly, starting at age 25-35
- Transvaginal ultrasound with color Doppler imaging every six months or yearly, beginning at age 25-35
- Yearly blood CA-125 testing, starting at age 25-35
- For women with a BRCA1 or BRCA2 alteration, they are also at an increased risk for breast cancer. Screening recommendations for them may include:
- Examining their own breasts monthly
- Examination of their breasts by a physician/nurse every six months or yearly, starting at age 25-35
- Mammograms (x rays of the breasts) yearly, starting at age 25-35
Specific screening programs may vary by physician. In addition to cancer screening, women with BRCA1 or BRCA2 alterations should know about their preventive surgery options. They may consider having their healthy ovaries and/or breasts removed, in order to reduce their risks to develop ovarian and/or breast cancer. Women may be more agreeable to having their ovaries removed because ovarian cancer is difficult to detect. However, this ends their ability to have children and automatically begins menopause for them. Both preventive surgeries greatly reduce a woman’s cancer risk, but they can never eliminate the risk entirely.
For people with cancer or at high risk for it, there often are support and discussion groups available. These may be invaluable for those who feel alone in their situation, because they can meet others who are dealing with the exact same issues.
Because ovarian cancer is not usually diagnosed until it is in an advanced stage, it is the most deadly of all the female cancers of the reproductive organs. Only 46% of women diagnosed with ovarian cancer will survive past five years. If ovarian cancer is diagnosed before it has spread to other organs, more than 90% of the patients will survive five years or more. Unfortunately, only 24% of all cancers are found at this early stage.
There appears to be no difference in how a woman with ovarian cancer will do, whether or not she has a BRCA alteration. Because unaffected people in a family with a BRCA alteration may be in high-risk screening programs, the hope is that they may be able to have any of their cancers detected earlier, giving a better prognosis.