Women who take the birth control pill for 10 years have nearly double the normal
risk of developing cervical cancer, but the risk begins falling as soon as they
stop and returns to near normal within 10 years, according to a study released
Thursday.
The study confirms previous research linking the pill with an increased risk of
cervical cancer and reveals for the first time that the risk falls after pill
use stops, said Dr. Jane Green, a University of Oxford clinical epidemiologist
who led the study, which was reported in the medical journal Lancet.
Green said that the pill's increased risk of cervical cancer -- like its
increased risk of breast cancer, revealed in previous studies -- is small and is
"outweighed by reduced risks for ovarian and womb cancer."
The results should "reassure women that fear of cervical cancer should not be a
reason not to take oral contraception," wrote Dr. Peter Sasieni, a professor at
the Queen Mary University of London, in an editorial accompanying the report.
Researchers were interested in how long the increased risk persisted, because
the incidence of cervical cancer peaks in women's 30s, several years after many
have stopped using the pill.
Green and her colleagues from the International Collaboration of Epidemiological
Studies of Cervical Cancer combined results from 24 studies involving more than
52,000 women in 26 countries.
In industrialized countries, they concluded, the overall rate of cervical cancer
among women who have never taken the pill is 3.8 cases per 1,000 women. The rate
rises to 4.0 per 1,000 in women who took the pill for five years and 4.5 for
those who took it for 10 years.
For women who are well-screened, Sasieni said, that translates into an
additional two cases per 10,000 women. In less-developed countries where
screening is not as prevalent, however, that translates to an increased risk of
about 40 cases per 10,000, he said.
The hormones contained in the pill are only a secondary cause of cervical
cancer, Green and Sasieni emphasized. The disease's primary cause is the human
papillomavirus. Researchers are not sure how the pill's hormones increase risk,
but they may work by making cervical cancer cells more susceptible to infection
or by accelerating the cancer's progression once an infection occurs.
Increased use of HPV vaccines should significantly reduce the incidence of the
disease, said Dr. Lesley Walker, director of Cancer Research UK, which sponsored
the study along with the World Health Organization and the International Agency
for Research on Cancer.
