Oncology

Oral Contraceptives Stave off Cancer after Use Stops

The reduced risk of ovarian cancer seen with oral contraceptives, though "somewhat attenuated over time," lasts for more than 30 years after these agents are discontinued, according to an analysis of patient-level data from numerous epidemiologic studies.

It is well-established that oral contraceptive use cuts the risk of ovarian cancer, Dr Valerie Beral and colleagues, from the Collaborative Group on Epidemiological Studies of Ovarian Cancer, point out. But what has been less clear, and is of key importance from a public health standpoint, is how long the protective effect lasts after women no longer take the pills.

To investigate, the researchers analysed data from 45 studies that included 23,257 women with ovarian cancer and 87,303 controls. They report their findings in the January 26 issue of The Lancet.

Thirty-one percent of case patients and 37 per cent of controls had ever used oral contraceptives, with corresponding average durations of use of 4.4 and 5.0 years, the report indicates. Consistent with previous reports, the risk of ovarian cancer fell as the duration of oral contraceptive use increased. However, as noted, even after stopping these drugs, protection was still apparent many years later.

Oral contraceptive use for five years followed by non-use for less than 10 years was associated with a 29 per cent reduced risk of ovarian cancer. As the period of non-use increased, the risk reduction fell; with 20 to 29 years of non-use, a 15 per cent reduction in risk was seen. Oral contraceptives appeared to have little effect on the risk of mucinous tumors, which accounted for 12 per cent of the malignancies seen.

The authors estimate that in high-income countries, the use of oral contraceptives for 10 years reduces the occurrence of ovarian cancer before age 75 from 1.2 to 0.8 cases per 100 users and cuts related mortality from 0.7 to 0.5 per 100 users.

Reuters Health