Ovarian cancer is the fifth leading cause of cancer death in women,
the leading cause of death from gynecological malignancy, and the
second most commonly diagnosed gynecologic malignancy .
It is idiopathic, meaning that the exact cause is usually unknown.
The disease is more common in industrialized nations, with the exception
of Japan. In the United States, females have a 1.4% to 2.5% (1 out
of 40-60 women) lifetime chance of developing ovarian cancer.
Older women are at highest risk. More than half of the deaths from
ovarian cancer occur in women between 55 and 74 years of age and approximately
one quarter of ovarian cancer deaths occur in women between 35 and
54 years of age.
The risk for developing ovarian cancer appears to be affected by several
factors. The more children a woman has, the lower her risk of ovarian
cancer. Early age at first pregnancy, older ages of final pregnancy
and the use of low dose hormonal contraception have also been shown
to have a protective effect. Ovarian cancer is reduced in women after
The link to the use of fertility medication, such as Clomiphene citrate,
has been controversial. An analysis in 1991 raised the possibility
that use of drugs may increase the risk for ovarian cancer. Several
cohort studies and case-control studies have been conducted since
then without providing conclusive evidence for such a link.  It
will remain a complex topic to study as the infertile population differs
in parity from the "normal" population.
There is good evidence that in some women genetic factors are important.
Carriers of certain mutations of the BRCA1 or the BRCA2 gene, more
frequent in some populations (e.g. Ashkenazi Jewish women) are at
a higher risk of both breast cancer and ovarian cancer, often at an
earlier age than the general population. Patients with a personal
history of breast cancer or a family history of breast and/or ovarian
cancer, especially if at a young age, may have an elevated risk. A
strong family history of uterine cancer, colon cancer, or other gastrointestinal
cancers may indicate the presence of a syndrome known as hereditary
nonpolyposis colorectal cancer (HNPCC, also known as Lynch II syndrome),
which confers a higher risk for developing ovarian cancer. Patients
with strong genetic risk for ovarian cancer may consider the use of
prophylactic oophorectomy after completion of child-bearing.
A Swedish study, which followed more than 61,000 women for 13 years,
has found a significant link between milk consumption and ovarian
cancer. According to the BBC, "[Researchers] found that milk
had the strongest link with ovarian cancer - those women who drank
two or more glasses a day were at double the risk of those who did
not consume it at all, or only in small amounts."  Recent
studies have shown that women in sunnier countries have a lower rate
of ovarian cancer, which may have some kind of connection with exposure
to Vitamin D.
Other factors that have been investigated, such as talc use, asbestos
exposure, high dietary fat content, and childhood mumps infection,
are controversial and have not been definitively proven.
"Associations were also found between alcohol consumption and
cancers of the ovary and prostate, but only for 50 g and 100 g a day."