NEW YORK, Aug 08 (Reuters Health) - Birth control pills with low doses of
the hormones estrogen and progestin appear to be just as effective at reducing
ovarian cancer risk as higher-dose pills, researchers report.
"The protection afforded by oral contraceptives against ovarian cancer
appears to be independent of the dose of estrogen or progestin," conclude Dr.
Roberta B. Ness of the University of Pittsburgh in Pennsylvania, and colleagues.
What's more, the protective effect of low-dose pills continued 30 years or
more after women stop taking them and occurred after as little as 1 year of
exposure, the authors report in the August 1st issue of the American Journal of
Epidemiology.
Birth control pills, or oral contraceptives, have been shown to lower a
woman's risk of developing ovarian cancer due to synthetic forms of the hormones
estrogen and progestin. However, high doses of these hormones are also
associated with increased risk of breast cancer and stroke.
For this reason, oral contraceptives with lower hormonal doses have replaced
earlier versions. While low-dose pills are equally effective as higher-dose
pills at suppressing ovulation, their effect on ovarian cancer risk is not
known.
In the study, nearly 800 women with ovarian cancer were compared with more
than 1,300 women who did not have cancer. Overall, women who used birth control
pills had a 40% lower risk of developing ovarian cancer. The risk was further
reduced the longer the duration of oral contraceptive use.
But the risk of developing ovarian cancer was the same for women who began
using oral contraceptives before 1972, when high-dose pills dominated the
market, and those who began using oral contraceptives after the 1980s, when
lower-dose pills were the norm. High-dose pills contain at least 50 micrograms
of estrogen.
"In summary, our findings indicate that oral contraceptive formulations in
common use today protect against ovarian cancer and that this effect continues
long after use has stopped," Ness and colleagues conclude.
