We know that ovarian cancer is more common in women whose ovaries have continued to produce eggs without interruption over their lifetimes. Every time you ovulate, the surface of the ovary splits open to let the egg out. When the surface cells grow rapidly in order to heal over the opening, they become more vulnerable to substances (carcinogens) that can cause abnormal changes in the cells. To date, the identity of these carcinogens is not certain. In order for cancer to develop, it is thought likely that a number of factors must be present: the presence of a carcinogen, some tendency to developing an abnormal growth of the ovarian cells, and uninterrupted ovulation that increase the chances of the carcinogen getting into the cell.
A number of factors have been shown to decrease a woman's risk of developing ovarian cancer. However, as seen in the table below, the decrease in risk associated with these factors is small. Events that prevent ovulation, such as pregnancy, breast -feeding, and taking birth control pills, will decrease your risk of developing ovarian cancer. During pregnancy, your ovaries do not produce any eggs for nine months. Breast- feeding, as a result of associated hormonal changes, keeps the ovaries at rest for an additional few months. Birth control pills work by preventing ovulation: the release of eggs from the ovary. Likewise, the late onset of your periods or early onset of menopause, which result in a decrease in the total number of times you ovulate in your lifetime, will also decrease your risk of getting ovarian cancer. Fewer ovulations lead to fewer vulnerable healing, rapidly dividing cells and less risk of ovarian cancer.
Genetic factors also appear to play a role in your risk of developing ovarian cancer. Caucasian women have a higher risk, as compared to women of African or Asian heritage. And, as discussed (LINK), a strong family history of ovarian cancer may increase your risk.
WOMEN AT LOW RISK FOR OVARIAN CANCER
A note about statistics: you probably already know that statistics need to be interpreted carefully. For instance if I tell you that your risk of ovarian cancer goes down 50% if you take birth control pills for more than 5 years, that sounds pretty good. And, it is good. But, it only changes your risk from 1 in 70 women during their lifetimes to 1 in about 140 women in their lifetimes. Another way to look at this is that without taking the pill, 98.6% of women will not get ovarian cancer and, for women who take the pill for 5 years or more, 99.3% of women will not get ovarian cancer.
- ONE OR MORE CHILDREN - decrease risk from 1 in 70, to about 1 in 140
- TAKEN BIRTH CONTROL PILLS (for more than one year) decreases risk from 1 in 70, to about 1 in 140.
- NO FAMILY HISTORY OF OVARIAN CANCER (see below)
- BLACK AND ASIAN WOMEN
- LATE ONSET OF PERIODS (after age 12) possibly decreases risk from 1 in 70, to about 1 in 77
- EARLY ONSET OF MENOPAUSE (before age 45) possibly decreases risk from 1 in 70, to about 1 in 84
WHAT IS YOUR RISK OF OVARIAN CANCER IF SOMEONE IN YOUR FAMILY HAS HAD IT?
The issue of family ovarian cancer has received a lot of attention from the press and caused a great deal of anxiety for many women. However, less than 10% of women found to have ovarian cancer have inherited this disease. Therefore, the vast majority (9 0 %) of women who get ovarian cancer have no family history of it. If someone in your family has had ovarian cancer, your risk will depend on how close the relative is to you, how old they were at the time they developed the disease, and how many of your relatives have had the disease. Knowing the specifics of your family history can either alert you to a possible problem or, more likely, be a source of reassurance.
Women with no family history of ovarian cancer have a 1.4% risk of developing ovarian cancer if they live to be 90 years old. Therefore, about 1 woman out of 100 will develop this disease in their lifetimes. To put this in some perspective, about 33 women out of 100 will die of heart disease and 20 women out of 100 will die of lung cancer. If your mother had ovarian cancer your risk of developing ovarian cancer increases to 7 out of 100 women. If your sister had ovarian cancer your risk is about 5 out of 100. Having a grandmother or aunt with ovarian cancer increases your risk to about 3 out of 100. If you have two or more close relatives with ovarian cancer your risk of developing ovarian cancer increases to 14 out of 100 women.
This information comes from studies of large numbers of women who have been diagnosed with ovarian cancer. However, the risk of inheriting ovarian cancer is higher in Jewish women of eastern European (Ashkenazi) descent where specific ovarian cancer gene mutations have been found to be more common. While only 1 out of 1,000 non Ashkenazi Jewish women has these particular mutations, about 20 out of 1,000 Ashkenazi Jewish women have these mutations. A non- Ashkenazi Jewish woman with one close relative with ovarian cancer has a 5% chance of having this mutation, while an Ashkenazi Jewish woman with one close relative with ovarian cancer has a 15% chance of having the mutation. For this reason, Ashkenazi Jewish women with a close relative with ovarian cancer might consider getting tested for this gene.
ARE THERE ANY MEDICATIONS THAT CAN DECREASE YOUR RISK OF OVARIAN CANCER?
Yes, believe it or not, birth control pills have been shown to decrease your risk of ovarian cancer. Continuous ovulation during your lifetime increases the risk of ovarian cancer. Birth control pills work by preventing ovulation, and thus decrease your risk. Even taking the pill for just one year will decrease your risk of ovarian cancer by about 10%. Taking the pill for 5 years or more decreases your risk by 50-70% . The same decreased risk associated with the use of birth control pills also appears to be true for women considered at high risk of developing ovarian cancer because of a strong family history.
Many people have had a fear or a distrust of taking birth control pills. Early studies, performed 20 years ago when the doses of the pill were extremely high, found a slightly increased risk of heart attack for women on the pill. But, for women on the low doses of hormone found in the pill today, the risk of a heart attack is less than 1 in 20,000. For comparison, the high levels of estrogen present during pregnancy increase the risk of heart attack to 1 in 10,000 women.
Unfortunately, the medical community has not communicated these positive facts adequately to the public. A recent study of women faculty, students and employees at Yale University found that 80% of these women did not know that the pill could decrease the risk of ovarian cancer.
CAN SOME TYPES OF SURGERY DECREASE YOUR RISK OF OVARIAN CANCER?
Surprisingly, both tubal ligation (getting your tubes "tied") and hysterectomy (without removal of the ovaries) have been shown to decrease the risk of subsequently developing ovarian cancer by almost 50%. Although the reasons for this decrease are not entirely clear, there are a few theories as to why this might be. Blocking off the tubes (tubal ligation) and removing the uterus (hysterectomy) both prevent any substances in the vagina from moving up inside the uterus and out the tubes, where they can land on the ovaries. Although these substances have not been identified, the theory suggests that once these substances are present on the ovary, they may induce the development of cancer. One substance that is a possible candidate for inducing ovarian cancer is talc. Talc has sometimes been found in the ovaries of women with ovarian cancer. Presumably this comes from talcum powder used in hygiene products, which may get into the vagina and then end up on the ovary. While the association between talc and ovarian cancer is still theoretical, if you are using a powder that is labeled as "talcum powder" or "containing talc", it is advisable to switch to another powder.
Another, more recent theory, is that damaging the tissues of a woman's reproductive organs may cause the body to form antibodies which destroy early ovarian cancer cells. Thus, the cells are destroyed before they have a chance to develop obvious ovarian cancer.
We in the medical field are still at the supposition and educated guess stage regarding the possible factors in the development of this worrisome disease.