February 2008
An analysis of 45 studies involving over 110,000 women has found the use of oral contraceptives provides long-term protection against ovarian cancer.
Background
The use of oral contraceptives has long been known to reduce the risk of ovarian cancer. This study brings together 45 studies from 21 countries providing more detail regarding:
- the extent of risk reduction,
- the length of time of the protective effect,
- the impact of different formulations of oral contraceptives, and
- the types of ovarian cancer affected.
Research findings
The researchers found that ten years use of oral contraceptives was estimated to reduce the incidence of ovarian cancer before the age of 75 from 12 cases per 1000 women to 8 cases per 1000 women. The same length of oral contraceptive use was also found to reduce ovarian cancer mortality from 7 deaths per 1000 women to 5 deaths per 1000 women.
Looking at this from a population level, the researchers suggest that during the past 50 years, 200,000 cases of ovarian cancer and 100,000 deaths have been prevented worldwide through use of the oral contraceptive pill.
The researchers also note the longer that women had used oral contraceptives, the greater the reduction in ovarian cancer risk. The reduction in risk is significant for more than 30 years after a woman stopped using oral contraceptives. However, the protective effect was found to slightly decrease over time.
The protective effect was similar for epithelial and non-epithelial ovarian cancers, but there was less evidence that oral contraceptives reduce the risk of mucinous tumours, which account for less than 15 per cent of all ovarian cancers.
There was no apparent difference in the level of risk reduction provided by oral contraceptive formulations taken during the 1960s, 1970s or 1980s.
National Breast and Ovarian Cancer Centre comment
This study provides strong evidence of the benefit of the oral contraceptive pill in providing a protective effect against ovarian cancer. However, it is also well established that there are certain risks associated with taking oral contraceptives including slightly increased risk of breast cancer and cervical cancer.
The primary reason for oral contraceptive pill use remains for contraceptive purposes rather than cancer prevention. The National Breast Cancer Centre recommends that women make decisions regarding the use of oral contraceptives in consultation with their general practitioner weighing up the risks and benefits based on their individual medical history.
Source
January 2008
- Ovarian cancer and oral contraceptives: collaborative reanalysis of data from 45 epidemiological studies including 23,257 women with ovarian cancer and 87,303 controls. The Lancet (371) Online 26 January 2008: 303-314.
