The ovaries are the sites of ovum (egg) production in women. They are also the main source of the hormones oestrogen and progesterone in premenopausal women. There are three types of ovarian tissue that can produce cancers: epithelial cells, which cover the ovary; stromal cells, which produce hormones; and germ cells, which become ova (eggs). About 85 to 90 per cent of ovarian cancers are epithelial carcinomas.
Incidence and survival rates
Ovarian cancer is the seventh most common cancer in women (and the 18th most common cancer overall) worldwide. Approximately 239,000 cases were recorded in 2012, accounting for nearly 4 per cent of all new cases of cancer in women (2 per cent overall). This cancer is usually fatal, and is the eighth most common cause of cancer death in women worldwide (14th overall).
Ovarian cancer incidence rates are greater in high than in middle- to low-income countries. Around the world, age-standardised incidence rates range from more than 11 per 100,000 women in Central and Eastern Europe to less than 5 per 100,000 in parts of Africa.
Ovarian cancer often has no symptoms at the early stages, so the disease is generally advanced when it is diagnosed. The five-year survival rate ranges from approximately 30 to 50 per cent.
Lifestyle factors and ovarian cancer risk
In this report from our Continuous Update Project (CUP) – the world’s largest source of scientific research on cancer prevention and survivorship through diet, nutrition and physical activity – we analyse global research on how certain lifestyle factors affect the risk of developing ovarian cancer. This webpage forms part of the World Cancer Research Fund/American Institute for Cancer Research Third Expert Report Diet, Nutrition, Physical Activity and Cancer: a Global Perspective.
Findings on ovarian cancer
There is strong evidence that:
- being tall INCREASES the risk of ovarian cancer
- being overweight or obese INCREASES the risk of ovarian cancer
There is some evidence that:
- breastfeeding might decrease the risk of ovarian cancer
Other causes of ovarian cancer
In addition to the findings on diet, nutrition and physical activity outlined above, other established causes of ovarian cancer include:
- life events
The risk of ovarian cancer is affected by the number of menstrual cycles during a woman's lifetime. Not bearing children, early menarche (before the age of 12) and late natural menopause (after the age of 55) all increase the risk of ovarian cancer. The reverse also applies: bearing children, late menarche and early menopause all reduce the risk of ovarian cancer. Tubal ligation (sterilisation) also decreases the risk of ovarian cancer.
Oral contraceptives protect against ovarian cancer. Use of hormone replacement therapy has been shown to increase risk.
Smoking tobacco increases the risk of mucinous ovarian cancer. It is estimated that 17 per cent of mucinous ovarian cancer cases are due to smoking tobacco.
- family history
Most ovarian cancers occur spontaneously, although five to ten per cent of cases develop due to a genetic predisposition. The latter, involving dysfunctional BRCA1 or BRCA2 genes, produces high-grade carcinomas, with poorer prognosis.
The pathogenesis of ovarian cancer is not well characterised, although various mechanisms have been suggested. Over many cycles of ovulation, the ovarian surface epithelium undergoes repeated disruption and repair. The epithelial cells are stimulated to proliferate, which increases the probability of spontaneous mutations. Alternatively, following ovulation, these cells may become trapped within the connective tissue surrounding the ovary, which can lead to the formation of inclusion cysts. If this happens, the epithelial cells are subjected to a unique pro-inflammatory microenvironment, which may increase the rate of DNA damage, thus affecting cancer risk.
Most ovarian cancers occur spontaneously, although 5–10 per cent of cases develop due to a genetic predisposition. The latter, involving dysfunctional BRCA1 or BRCA2 genes, produces high-grade carcinomas, with a poorer prognosis.
Full references and a summary of the mechanisms underpinning all the findings can be found in the ovarian cancer report.
How the research was conducted
The global scientific research on diet, nutrition, physical activity and the risk of ovarian cancer was systematically gathered and analysed, and then independently assessed by a panel of leading international scientists in order to draw conclusions about which of these factors increase or decrease the risk of developing this cancer.
Published findings in peer-reviewed journals
Selected findings from this report have been published in peer-reviewed journals. Details of the papers and links to the abstract in PubMed are below:
Anthropometric factors and ovarian cancer risk: A systematic review and non-linear dose-response meta-analysis of prospective studies. Aune D, Navarro Rosenblatt DA, Chan DS, Abar L, Vingeliene S, Vieira AR, Greenwood DC, & Norat T. Int J Cancer 2015; 136(8): 1888-98. Abstract
This webpage is a summary.
For much more, download the full chapter.