Description
The most common gynecologic cancer in the United States, ovarian cancer is the fourth leading cause of cancer death. There are many types of ovarian cancer, depending on the nature of the origin of the ovary cell affected. Epithelial ovarian cancer is the most prevalent, accounting for about 90 percent of cases.
This insidious disease is frequently detected after it has already spread to other areas of the body. The most common symptoms include stomach swelling, unusual vaginal bleeding, pelvic pressure, back or leg pain, and gas and bloating.
Statistics
Ovarian cancer can affect women of any age, though it most often occurs in women over 60. While the rate of ovarian cancer has been declining for more than a decade – its incidence has fallen about 1.4 percent since 1991 – the disease remains the fifth most common cancer in women, accounting for about 3 percent of all female cancers. An estimated 22,220 new cases will be diagnosed in the United States in 2005, and approximately 16,210 women are expected to die from it. A woman’s risk of developing ovarian cancer during her lifetime is about 1 in 70; the risk of getting the cancer and dying from it is 1 in 98.
Younger women with ovarian cancer live longer. Those younger than 65 are about twice as likely (59 percent) to live five years after diagnosis than women 65 or older (29 percent). About 77 percent of newly diagnosed ovarian cancer patients live one year after diagnosis. The five-year relative survival rate for all stages is 44 percent.
Approximately 94 percent of women who are diagnosed with ovarian cancer in the early stages live at least five years, though this accounts for only about 19 percent of all cases.
Early Detection, Diagnosis
No reliable routine screening tests exist for ovarian cancer, nor does it manifest any distinguishing symptoms, making it difficult to detect early. Only about one-fourth of these cancers are found at an early stage.
The blood level of a protein, CA-125 – which is made by some ovarian cancer cells – is used as part of a battery of tests to gauge the effectiveness of chemotherapy and to look for disease recurrence, but its use for early detection is controversial to date and under continuing study.
The National Cancer Institute-sponsored Prostate, Lung, Colorectal and Ovarian Screening Trial, aimed at determining whether certain screening tests can reduce the number of deaths from cancer, is looking at whether a pair of tests – a blood test for CA-125 and transvaginal ultrasound – can do just that. CA-125 levels may go up in women with ovarian cancer, but they also may rise during pregnancy and menstruation, and in the presence of endometriosis, benign ovarian tumors, and with other cancers.
Transvaginal ultrasound uses sound wave echoes to create a picture of the ovary. Healthy tissues, fluid-filled cysts, and cancer produce different echoes, and the test is useful in diagnosing ovarian diseases.
While additional panels of tumor markers are being studied, other researchers are looking to proteomics, studying patterns of proteins in the blood of ovarian cancer patients that might lead to early detection.
If cancer is suspected, imaging studies, including ultrasound and CT (computed tomography) scans may be done. In the latter, an X-ray beam takes a series of pictures, and a computer forms a detailed image.
About 5 to 10 percent of ovarian cancers are caused by an aberrant BRCA1 or BRCA2 gene, which also greatly increases the risk for developing breast cancer. Women carrying a mutation in BRCA1 or BRCA2 have an estimated 40 to 50 percent lifetime risk of developing ovarian cancer by age 70. Otherwise, the risk is low – only 1.7 percent.
Minimizing Risk/Prevention
Though its cause is unknown, there are several factors associated with a heightened risk of developing ovarian cancer. Knowing about these risk factors, for the most part, however, has not yielded effective ways to prevent the disease.
Having a family history of ovarian cancer – especially in first degree relatives (mother, daughter or sister) – increases the risk of developing the disease. Genetic counseling may be recommended to consider testing for the BRCA1 or BRCA2 gene mutations.
Women who never have had children may be at greater risk for ovarian cancer, as are women who have had breast or colon cancer. Taking fertility drugs and increasing ovulation appears to increase the risk. Taking birth control pills for three years or more decreases the risk of ovarian cancer. Tubal ligation or hysterectomy, especially after childbearing, is also associated with a lower risk.
For women who have BRCA mutations, having surgery to remove the ovaries has proven to substantially reduce the risk of ovarian cancer.
Latest Research
Researchers are continuing to study targeted therapies to see which should be tested in combination with various chemotherapy drugs to treat ovarian cancer. A monoclonal antibody drug called Avastin, for example, blocks VEGF, a protein that stimulates the growth of new blood vessels that help the tumor grow and spread, a process called angiogenesis. Avastin currently (March 2005) is under study in several different clinical trials and has shown promise for ovarian cancer. One trial looks at the ability of Avastin to halt disease progression, while another asks if adding Avastin to two standard chemotherapy drugs – carboplatin and paclitaxel – works better in helping patients live longer.
While there currently is much interest among scientists regarding the promise of Avastin, the majority of targeted drug studies for ovarian cancer to date have focused on the epidermal growth factor receptor (EGFR), which is expressed in approximately 30 percent to 70 percent of such cancers. EGFR inhibitors work by blocking a signaling pathway that cancer cells need to grow.
Among other targets for drug development are molecular pathways involving the cancer-blocking gene p53 and the cancer-promoting gene family, BCL-2.
Current Treatment
The outlook for ovarian cancer patients has improved over the last decade, in large part due to the use of platinum- and taxane-based chemotherapy. Surgery is initially used to both determine the extent of disease and to remove the cancer, with the goal of leaving as little disease as possible. In early stage ovarian cancer, surgery frequently can cure the patient, leaving no disease behind. Surgery is followed by a standard combination chemotherapy with paclitaxel and carboplatin. The majority – 75 percent – of patients with advanced disease responds to this therapy, and approximately 50 percent have no evidence of cancer after surgery and chemotherapy according to the standard measures, which include a normal physical exam, CT scan and CA-125 blood levels. But the disease returns in most of these patients in a little less than two years, and one-half of them will die of the disease two years later, although many patients can survive for longer periods of time.
Several studies are looking at improving chemotherapy, trying different combinations of drugs. One study – an international, randomized trial with about 4,000 patients with advanced ovarian cancer – is comparing the results of five different drug combinations to see which drug groups might help individuals live longer.
Some clinicians are studying the effectiveness of experimental stem cell transplants for advanced ovarian cancer. Other researchers are attempting to use standard drugs in new ways. Drugs such as gemcitabine, doxorubicin and topotecan, which have had some success in helping patients in whom ovarian cancer has returned, are being tried as first-time treatments in women to see if they might be effective.
As scientists continue to learn more about the biology of ovarian cancer, many are convinced that the ability to create individual molecular profiles of patient tumors will enable them to match specific treatments with biochemical abnormalities – another step in making ovarian cancer more of a chronic disease individuals can live with.
Resources
National Cancer Institute
1-800-4-CANCER
www.cancer.gov
American Cancer Society
1-800-ACS-2345
www.cancer.org
National Ovarian Cancer Coalition, Inc.
1-888-OVARIAN
www.ovarian.org