US scientists found, some pills with high levels of
oestrogen can raise the risk threefold, compared with that of women who have
never used the pill or who have stopped using it.
The study conducted by the Fred Hutchinson Cancer
in Seattle also states that the pills containing low-dose
hormones carried no extra risk.
Dr Elisabeth Beaber of the Center said that the results of
the study suggested use of contemporary oral contraceptives in the past year
was associated with an increased breast cancer risk 'relative to never or
former oral contraceptive use.
This risk may vary by oral contraceptive formulation. "Our
results require confirmation and should be interpreted cautiously," she said.
Previous studies have suggested the increased risk declined
after women stopped taking the pills, Dr Elisabeth added.
The study involved 23,000 women and claims to be the first
to look at up-to-date formulations of oral contraceptives used in the 1990s and
It compared 1,102 in whom breast cancer had been diagnosed
and 21,952 without the disease. Those with breast cancer were aged 20 to 49
years, with cancer having been diagnosed between 1990 and 2009.
Pills containing high-dose oestrogen raised breast cancer
risk 2.7-fold, or 170 per cent, while those with moderate-dose oestrogen
increased the risk 1.6-fold.
Pills containing low-dose oestrogen did not increase breast
cancer risk. Across recent use of all pills, breast cancer risk increased by 50
per cent, compared with never or former use.
Meanwhile, Sarah Williams at Cancer Research UK said women
should not stop taking the Pill on the basis of this study and discuss any
concern with their GP or family planning service.
The study was published in Cancer Research
, a journal
of the American Association for Cancer Research.