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Tuesday, 1 January, 2002, 23:46 GMT
Pill hormone 'cuts cancer risk'
Pill packs
The pill may cut cancer risk
Oral contraceptives with higher levels of the hormone progestin seem to be most effective at reducing a woman's risk of ovarian cancer, say scientists.

The pill has long been associated with a decreased risk of ovarian cancers.

Some studies show that using it for at least three years reduces the risk of developing cancer in the lining of the ovaries by up to 50%.

If reduction in ovulation alone was the only protective effect of oral contraceptives, then we would find that all formulations had the same reduction in risk

Dr Joellen Schildkraut
The longer you take it, the smaller the risk.

It has commonly been thought that this protective effect is down to the reducing the number of times a woman ovulates.

However, a study by a team from Duke University Medical Center in the US indicates that the progestin level in oral contraceptives might be as important. Progestin is a synthetic form of the female sex hormone progesterone.

Different effects

The researchers studied 390 women with epithelial ovarian cancer and 2,865 control subjects.

Researcher Dr Joellen Schildkraut said: "If reduction in ovulation alone was the only protective effect of oral contraceptives, then we would find that all formulations had the same reduction in risk.

"That's not what we found in this study."

The study showed that women who took pills with higher progestin levels showed a significant reduction in risk.

The effect held good even when the pills were taken for a short period of time.

Levels of oestrogen, another hormone contained in oral contraceptives, did not seem to have any impact on the risk of developing ovarian cancer.

Women who did not take the pill at all seemed to be at the greatest risk of developing the disease.

Biological effects

The findings of the study by a second piece of research conducted at Duke into the biological effects of progestin.

This study, carried out on monkeys, suggests that progestin is linked to a more rapid turnover of cells in lining, or epithelium, of the ovaries.

The researchers believe that if the cells in the ovarian epithelium live for a shorter period, there is a greater chance of eliminating damaged cells that can turn cancerous.

Dr Schildkraut warned that while pills that are higher in progestin are protective against ovarian cancer, they might increase risk of certain types of breast cancer.

She said other agents, such as vitamin D, may be able to have the same positive effect without increasing breast cancer risk.

She also admitted the study did have limitations. For instance, the average age of the women who took part was just 44 compared with an average age of 59 for women who develop ovarian cancer in the general population.

This makes it difficult to know whether these results would apply to menopausal women who develop ovarian cancer.

Hormone levels cut

Dr Anne Szarewski, of the Imperial Cancer Research Campaign, told BBC News Online that the study was interesting, but not conclusive.

She said the amount of progestin, and other hormones included in the pill had been cut in recent years because of fears that they might increase the risk of cardiovascular disease.

She said: "All contraceptive pills, no matter what their dose of progestin, seem to confer protection against ovarian cancer.

"It is likely that this is primarily due to the effect on ovulation, but it might be that there is an extra benefit from higher levels of progestin."

However, Dr Szarewski said the contraceptive injection Depo Provera had not been shown to protect against ovarian cancer, despite containing progesterone at levels much higher than those found in any contraceptive pill.

The research is published in the Journal of the National Cancer Institute.

See also:

15 Nov 01 | Health
Ovarian cancer rates soar
07 Jan 99 | Health
A short history of the pill
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