Information about the prevention of cancer and the science of screening appropriate individuals at high risk of developing cancer is gaining interest. Physicians and individuals alike recognize that the best "treatment" of cancer is preventing its occurrence in the first place or detecting it early when it may be most treatable.

Ovarian cancer has the highest mortality rate of all gynecologic cancers. It is the fifth leading cause of cancer death among U.S. women, with a projected 23,000 new cases and 14,000 deaths in the year 2001. The causes of ovarian cancer are poorly understood. However, researchers have evaluated risk factors associated with ovarian cancer. A few risk factors have been identified and others are suspected.

The chance of an individual developing cancer depends on both genetic and non-genetic factors. A genetic factor is an inherited, unchangeable trait, while a non-genetic factor is a variable in a person's environment, which can often be changed. Non-genetic factors may include diet, exercise, or exposure to other substances present in our surroundings. These non-genetic factors are often referred to as environmental factors. Some non-genetic factors play a role in facilitating the process of healthy cells turning cancerous (i.e. the correlation between smoking and lung cancer) while other cancers have no known environmental correlation but are known to have a genetic predisposition. A genetic predisposition means that a person may be at higher risk for a certain cancer if a family member has that type of cancer.

Heredity and Genetic Factors

Research has determined that 5-10% of all women with ovarian cancer have a genetic predisposition to the disease. This means that women with a family history (mother or sister) of ovarian cancer are at an increased risk of developing the disease.

The majority of hereditary ovarian cancers occur in women with a specific genetic abnormality. This is referred to as the BRCA1 or BRCA2 gene, which are located on chromosomes 17 and 13, respectively. Women with the BRCA1 gene have an 85% risk of developing breast cancer, a 60% risk of developing ovarian cancer by age 70 and an increased risk of colon cancer. Individuals with the BRCA2 gene are also at an increased risk, although their risk is lower than those with the BRCA1 gene.

Environmental or Non-Genetic Factors

Clinical research has suggested that increasing age, the use of hormone replacement therapy after menopause, the use of fertility drugs, exposure to talcum powder, and a high-fat diet may increase the risk of developing ovarian cancer.

In one clinical study, researchers examined risk factors such as a family history of ovarian cancer, a later age at menopause, not using oral contraceptives, not getting pregnant, a low intake of vegetables and a high intake of fat and concluded that these risk factors accounted for 51% of the ovarian cancer cases. These findings, and those of future studies, will help to further develop the understanding of what causes ovarian cancer and to focus more effectively on strategies to prevent this disease.

Prevention

Cancer is largely a preventable illness. Two-thirds of cancer deaths in the U.S. can be linked to tobacco use, poor diet, obesity, and lack of exercise. All of these factors can be modified. Nevertheless, an awareness of the opportunity to prevent cancer through changes in lifestyle is still under-appreciated.

Some studies have indicated that women may reduce their risk of developing ovarian cancer by using oral contraceptives, giving birth to at least one child, breastfeeding and having a hysterectomy or tubal ligation. In addition, women may want to avoid fertility drugs, talcum powder and a high-fat diet.

Removal of the Ovaries: In women who have a strong family history of ovarian cancer or the presence of the BRCA1 or BRCA2 genes, removal of the ovaries may be effective prevention of ovarian cancer; however, this procedure has not been proven to prevent cancer in all cases. Researchers also lack sufficient documentation that this is the optimal approach for young women. Women with the BRCA1 or BRCA2 gene need to consider the potential for complications and side effects before committing to this procedure. Once the ovaries are removed, women no longer produce estrogen and may need long-term hormone replacement. In addition, there are other risks associated with early menopause.

Oral Contraceptives: The use of oral contraceptives in women with the BRCA1 or BRCA2 gene may reduce the risk of ovarian cancer by 40-50% and is currently the most frequent treatment recommended in younger women with these genetic abnormalities.

Diet: Diet is a fertile area for immediate individual and societal intervention to decrease the risk of developing certain cancers. Numerous studies have provided a wealth of often-contradictory information about the detrimental and protective factors of different foods.

There is convincing evidence that excess body fat substantially increases the risk for many types of cancer. While much of the cancer-related nutrition information cautions against a high-fat diet, the real culprit is an excess of calories. Studies indicate that there is little, if any, relationship between body fat and fat composition of the diet. These studies show that excessive caloric intake from both fats and carbohydrates have the same result of excess body fat. The ideal way to avoid excess body fat is to limit caloric intake and/or balance caloric intake with ample exercise.

It is still important, however, to limit fat intake, as evidence still supports a relationship between cancer and polyunsaturated, saturated and animal fats. Specifically, studies show that high consumption of red meat and dairy products can increase the risk of certain cancers. One strategy for positive dietary change is to replace red meat with chicken, fish, nuts and legumes.

High fruit and vegetable consumption has been associated with a reduced risk for developing at least 10 different cancers. This may be a result of potentially protective factors such as carotenoids, folic acid, vitamin C, flavonoids, phytoestrogens and isothiocyanates. These are often referred to as antioxidants.

There is strong evidence that moderate to high alcohol consumption also increases the risk of certain cancers. One reason for this relationship may be that alcohol interferes with the availability of folic acid. Alcohol in combination with tobacco creates an even greater risk of certain types of cancer. Although excessive alcohol ingestion and all tobacco use are best avoided, they are not major causes of ovarian cancer.

Exercise: Higher levels of physical activity may reduce the incidence of some cancers. According to researchers at Harvard, if the entire population increased their level of physical activity by 30 minutes of brisk walking per day (or the equivalent energy expenditure in other activities), we would observe a 15% reduction in the incidence of colon cancer. The association between exercise and ovarian cancer is not as well defined.

Screening and Early Detection of Ovarian Cancer

For many types of cancer, progress in the areas of cancer screening and treatment has offered promise for earlier detection and higher cure rates. The term screening refers to the regular use of certain examinations or tests in persons who do not have any symptoms of a cancer but are at high risk for that cancer. When individuals are at high risk for a type of cancer, this means that they have certain characteristics or exposures, called risk factors that make them more likely to develop that type of cancer than those who do not have these risk factors. The risk factors are different for different types of cancer. An awareness of these risk factors is important because 1) some risk factors can be changed (such as smoking or dietary intake), thus decreasing the risk for developing the associated cancer; and 2) persons who are at high risk for developing a cancer can often undergo regular screening measures that are recommended for that cancer type. Researchers continue to study which characteristics or exposures are associated with an increased risk for various cancers, allowing for the use of more effective prevention, early detection, and treatment strategies.

The predictive value of screening may be greater for women who are at a high risk of developing ovarian cancer, but whether screening will allow for early detection and improve survival among such women remains unknown.

Annual Pelvic Examination: Currently, the most widely utilized way to detect ovarian cancer is to undergo a complete gynecologic examination at least once per year. Because ovarian cancers begin deep in the pelvis, they often do not cause any symptoms until they are at an advanced stage. In order to improve outcomes for women with ovarian cancer, the disease has to be diagnosed early, before it spreads.

Strategies to Improve Screening and Early Detection

Unfortunately, due to a lack of definitive symptoms, the majority of women with ovarian cancer are not diagnosed until their cancer has reached an advanced stage, when it is considered incurable. For this reason, ovarian cancer has been referred to as the “silent killer.” However, some recent studies have indicated that the majority of women with ovarian cancer actually do experience symptoms prior to their diagnosis. Since symptoms may be discreet and vary from person to person, many women and/or their physicians may not associate the symptoms with ovarian cancer. The symptoms include abdominal abnormalities such as increased abdominal size, abdominal bloating and abdominal pain. Other frequently experienced symptoms are indigestion, abnormal vaginal bleeding, constipation, pelvic pain, urinary frequency or incontinence, pain with intercourse, nausea, fatigue, back pain and diarrhea.

Several new methods of screening have been tried, but none have been uniformly successful. These include transvaginal ultrasound, the measurement of serum CA-125 and genetic testing for BRCA1 and BRCA2. While these options have yet to become standard procedure, they may play a role in the early detection of ovarian cancer in selected patients in the future.

Transvaginal Ultrasound: Two recent clinical studies have shown that transvaginal ultrasound may be an effective screening technique for detecting ovarian cancer. During a transvaginal ultrasound, a receiver is inserted into the vagina. The receiver transmits sound waves to create a picture of internal structures. Because cancerous tumors are a different density than normal tissue, the sound waves create a different pattern when they bounce off of the cancer. Transvaginal ultrasound has been used to detect stage I and stage II ovarian cancer in many women, dramatically increasing chances for a cure. These early stage cancers probably would not have been detected by a normal pelvic examination. Women over 50 and women at a high risk for developing ovarian cancer may want to speak with their physicians about including this test in their annual examination.

CA-125: Elevated levels of the protein CA-125 in the blood have been associated with ovarian cancer. However, elevated CA-125 levels do not necessarily suggest ovarian cancer because CA-125 levels can be elevated in a number of other cancers, benign conditions and during the first trimester of pregnancy. The normal level of CA-125 is less than 35 units per milliliter in the blood. In general, the higher the level of CA-125 found, the greater the chance of having ovarian cancer, especially for women past menopause.

Predictive Genetic Testing: The identification of cancer susceptibility genes has led to predictive genetic testing. The breast cancer susceptibility genes, BRCA1 and BRCA2, have also been associated with an increased risk of ovarian cancer. Since most ovarian cancers are not the result of known inherited mutations, not all women would benefit from genetic testing. However, women who appear to be at a high risk may benefit from undergoing a test to determine if they do carry the BRCA1 or BRCA2 gene. An accurate genetic test can reveal a genetic mutation, but cannot guarantee that cancer will or will not develop. At this point, genetic tests are used to identify individuals who are at an increased risk of developing cancer, so that these individuals may have the option of taking preventive measures, such as increased surveillance.