The term ‘ovarian cancer’ describes cancers that appear to arise in the ovary. However, we now know that many of the cancers that are called ovarian cancers actually start in the fallopian tubes which carry the eggs from the ovary to the uterus or womb. They then spread to the ovaries.
It is estimated that 1,532 women will be diagnosed with ovarian cancer in 2020 and 1,068 women will die from the disease. In Australia, ovarian cancer is the 10th most common type of cancer in women and the second most common type of gynaecological cancer after cancer of the uterus, and women have a 1 in 85 chance of being diagnosed with ovarian cancer before their 85th birthday. Ovarian cancer is most common in women over the age of 60.
Women who have a defect in one of the breast cancer or BRCA genes have a greatly increased risk of developing ovarian as well as breast cancer. However, these mutations are rare and they only account for about one tenth of all ovarian cancers. Women with endometriosis are also more likely to develop ovarian cancer. In contrast, pregnancy, breastfeeding and use of the contraceptive pill all reduce a woman’s risk of developing epithelial ovarian cancer.
Ovarian cancer is sometimes called the ‘silent killer’ because it does not cause distinctive symptoms and is hard to diagnose. This means that the cancers have often spread beyond the ovaries by the time they are diagnosed. Cancers that have spread are harder to treat and they often come back after treatment has finished. As a result, survival rates for ovarian cancer are worse than for many other cancers and fewer than five of every ten women diagnosed with ovarian cancer will still be alive five years later. This means that, although ovarian cancer is the 10th most common cancer in Australian women, it is the 6th most common cause of cancer death.
Ovarian cancer is not a single disease. Even within the main group of ‘epithelial’ ovarian cancers, there are several different types of cancer and they have different risk factors and respond differently to treatment. For example, one type is more common in women who smoke and other types seem to be more common in women who are overweight or obese. Even within these groups, we now know there are subtypes with different molecular changes and these also affect how the cancers respond to different drugs. This makes ovarian cancer challenging to study because we need to look at the different types separately and need to develop different therapeutic strategies to target the more aggressive forms of ovarian cancers.
There is currently no screening test for ovarian cancer and, aside from reducing rates of obesity and stopping women smoking which will prevent a small proportion of cases, we do not have a simple method to prevent women from developing it.