(January 24, 2008 - Insidermedicine) Oral contraceptive use provides substantial protection against ovarian cancer, with the level of protection increasing the longer the drug is taken, according to a meta-analysis published in The Lancet.

Here are some facts about ovarian cancer:

•    Worldwide, more than 190,000 new cases of ovarian cancer occur each year, accounting for around 4% of all cancers diagnosed in women.

•    Incidence rates for ovarian cancer vary considerably by geographical region. The highest rates are in the USA and Northern Europe, and the lowest rates in Africa and Asia.

•    Ovarian cancer occurs mainly in older women, with the vast majority being diagnosed in women over the age of 50.

Researchers from the Collaborative Group on Epidemiological Studies of Ovarian Cancer conducted a meta-analysis of 45 epidemiological studies of ovarian cancer. Together, these studies included data on over 23,000 women with ovarian cancer, 31% of whom had used oral contraceptives at some point in their lives, and over 87,000 women without ovarian cancer, 37% of whom had a history of using oral contraceptives.

In high income countries, where rates of ovarian cancer are highest, ten years of oral contraceptive use reduced ovarian cancer incidence before age 75 from an estimated 12 per 1,000 to 8 per 1,000. It also reduced mortality from ovarian cancer from an estimated 7 per 1,000 to 5 per 1,000. Every 5,000 woman years of oral contraceptive use prevented about two ovarian cancers and one death from ovarian cancer before age 75. Changes in hormone dose of oral contraceptives throughout the years did not appear to have an impact on their effect on ovarian cancer risk.

Based on these findings, the authors conclude that oral contraceptive use confers long-term protection against the development of ovarian cancer. This adds a new dimension to the risk/benefit analysis of taking oral contraceptives.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.