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Contraceptive pills may protect even highly vulnerable women
Doctors have long known that the hormones in oral contraceptives cut the risk of ovarian cancer by at least 50%.
But a new study, published in the New England Journal of Medicine, shows that the benefits also extend to women who carry the cancer gene mutations BRCA1 and BRCA2 which make them more prone to developing tumours.
Much bigger risk
Women with BRCA1 are up to 45% more likely to develop ovarian cancer. The risk is 25% among women with BRCA2.
Doctors sometimes recommend that women carrying the genes have their ovaries surgically removed once they have finished having children.
Researchers looked at 207 women with ovarian cancer whose DNA carried either the BRCA1 or BRCA2 mutation.
Women who took an oral contraceptive for six or more years had a risk reduction of 60%.
For women who took "the pill" for three years or less, the contraceptives cut the ovarian cancer rate by 20 percent.
More research required
However the scientists warned more research was required before oral contraceptives could be recommended as a way to prevent ovary tumours.
The BRCA1 and BRCA2 also increase the risk of breast cancer and it is unknown what the impact of oral contraceptives is on that risk.
In some studies, birth control pills seem to be responsible for elevating the risk of breast cancer, perhaps by 10 to 20%. But not all studies have confirmed that.
The researchers also warned that different oral contraceptives contain different combinations of hormones, and their findings do not show if one hormone mixture is better than others at preventing ovarian cancer.
They noted that surgery was still the most effective way to prevent ovariain cancer.
Never having been pregnant, eating fatty foods, taking fertility drugs and using talcum powder may also increase the risk of ovarian cancer.
'Exciting' research
Professor Gordon McVie, director general of the Cancer Research Campaign, said more research was needed before firm conclusions could be drawn.
But he said the new study opened up a potentially rich avenue of investigation which could yield more details of the mechanism of ovarian cancer.
Professor McVie said: "It is really quite exciting. We have now got the technology to identify people at risk, but as yet we do not have anything to offer them."