Women taking birth control pills have a 50 per cent higher
overall risk of developing breast cancer, a new study has found.
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 Research Center in Seattle also states that the pills containing low-dose hormones carried no extra risk.
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 2000s.
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.