Ovarian Cancer. EPIDEMIOLOGY AND DIAGNOSIS
About 26,800 women are diagnosed with ovarian cancer each year in the United States. Of these women, approximately 14,200 will die of the disease. Ovarian cancer represents 55% of all deaths from gynecologic cancer. The risk of a woman developing ovarian cancer during her lifetime is 1-2%. The incidence varies with age and is 1.4 per 100,000 in women under age 40 years and 38 per 100,000 in women older than age 60 years. Figure 4 illustrates the prevalence of different types of ovarian cancer by age. Ovarian cancer is more common in Northern European and North American countries than in Asia, developing countries, or southern continents.
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The etiology of ovarian cancer is not known, but risk factors include infertility, low parity, or both; use of talc on the perineum; high-fat diet; lactose intolerance; history of breast or colon cancer; and a family history of ovarian cancer. Smoking, alcohol use, coffee consumption, estrogen replacement therapy, and viral infections (such as mumps) have not been associated with increased risk. Use of oral contraceptives, however, is protective for ovarian cancer, with an average relative risk of about 0.7 for women who have used oral contraceptives for 2 years and a 0.5 relative risk for women who have used oral contraceptives for 5 years or more. The protective effect of oral contraceptive use appears to be long term, with some studies indicating a lifetime risk reduction.
Table 6 illustrates the relative stage at diagnosis and the survival by stage for ovarian cancer in relation to other gynecologic cancers. The 5-year survival rate for ovarian cancer by stage is not significantly different from the 5-year survival rate for other gynecologic cancers; however, there is a significant difference in stages, with ovarian cancer usually having spread into the abdomen in about two thirds of patients at the time of diagnosis. It is clear from these data that the single most important factor in the large number of deaths from ovarian cancer is the failure to diagnosis the disease at an early stage. The reasons for this failure correspond to the growth and spread patterns of the disease. Because the ovary floats freely in the pelvic cavity, a tumor can grow for some time without producing symptoms associated with involvement of, or pressure on, other organs.