A new study has revealed that longer hormone replacement therapy (HRT) can dramatically increase women's chances of developing breast cancer. The research led by scientists in California has found that the risk was 83 percent greater for those using the oestrogen and progesterone combined pill for 15 or more years. "This study confirms that risk is increased for women who are using HRT, but that it gradually returns to normal after stopping treatment," express.co.uk quoted Dr Claire Knight, of Cancer Research UK, as saying. The study is the latest in a string of conflicting reports. John Stevenson, a HRT expert at London's Royal Brompton Hospital, said: "The risk is less than that seen with so many physical and lifestyle factors. "So women should not be put off taking HRT for any length of time if they need it."