| The protection that birth control pills help give against ovarian
cancer may not come from their disruption of ovulation, as previously assumed, but from
the direct action of the hormone progestin in the pills, researchers reported on Sunday. The
finding could lead to better ways to fight ovarian cancer -- the fourth-leading cause of
cancer deaths among women -- both among women who take the pills and those who do not, the
scientists said.
Previous research has found that routine use of oral contraceptives for as little
as three years can decrease ovarian cancer risk by as much as half, according to the
studies released at the annual meeting of the Society of Gynecologic Oncologists. But
little research has been done into what is behind the effect.
"Since the birth control pill inhibits ovulation, it has been presumed that
the pill's protective effects occur in conjunction with stopping the ovulation
cycle," said Gustavo Rodriguez of Duke University Medical Center in Durham, North
Carolina.
"What is exciting is that for the first time, these findings suggest that it
may be the progestin component in oral contraceptives that provides the greatest
protection -- in a biologic way that is totally unrelated to ovulation inhibition,"
he said.
IMPLICATIONS SPELLED OUT
"The implications of these findings could be very far-reaching," he
said.
"If the mechanism by which the birth control pill protects against ovarian
cancer is well understood and involves a biologic effect unrelated to effects on
ovulation, then it may be possible to develop birth control pills in formulations that
would provide enhanced ovarian cancer prevention benefits and to develop a pharmacologic
preventive strategy that can benefit all women -- including menopausal women, for example,
who don't ovulate and who represent one of the groups of women at greatest risk of ovarian
cancer."
Rodriguez collaborated on the two studies, both of which were done at Duke.
One involved more than 3,000 women, some with cancer and others without, who were
questioned about birth control pill use. It found that high-potency progestin pill
formulations appeared to be twice as protective as low-potency ones against the
development of ovarian cancer.
By contrast, no difference was detected in the protective effect of high vs. low
concentrations of estrogen in oral contraceptives.
The second study involved research on macaque monkeys and was designed to
determine exactly how progestin might act within the ovary. It found that the hormone had
a beneficial effect on the production of transforming growth factor beta, a molecule known
to have cancer-preventing properties. |
