"Beyond the fact that they provide an effective means of contraception and may benefit women with dysmenorrhea or menorrhagia, the use of oral contraceptives is associated with substantial reductions in the risks of ovarian, endometrial, and colorectal cancers later in life", he wrote, highlighting this further emphasizes the need for a new form of hormonal contraceptive that does not carry an associated breast cancer risk.
Use of oral contraceptives may increase risk of breast cancer, although the overall absolute increase was relatively small, according to a study from Denmark.
Compared to what the group of researchers found in one of their other papers-that using hormonal contraception was associated with a 300 percent increase in suicide risk-"it is a modest increase", said Dr. Øjvind Lidegaard, one of the authors of the paper and a gynecologist at the University of Copenhagen.
However, the absolute risk for developing breast cancer for most women is extremely low.
"There had been some changes to oral contraceptive formulations in the '90s, and there was the hope those formulations would result in a lower risk of breast cancer", said Gaudet, who was not part of the study. "But we should make an individual assessment-doctor and a woman, together-to see what is the most appropriate thing for her to use". Using hormonal contraception for less than one year did not increase women's risk of breast cancer.
The study builds on earlier findings linking hormonal birth control and breast cancer, but the new study focused on newer forms of birth control. After all, it means that almost a quarter of American women are doing something that might increase their risk of developing breast cancer by a third-in theory. But these earlier studies looked mainly at older types of birth control pills, which had a higher dose of estrogen than today's pills. Relative to the increased risk posed by other environmental factors, like smoking for lung cancer-that's about a 10 times greater risk-and having a human papillomavirus infection for cervical cancer-that may increase risk about 50 or 60 times-38 percent really isn't that much.
The new study "confirms that the increased breast cancer risk. that was initially reported with the use of older, often higher-dose formulations also applies to contemporary formulations" of birth control, David Hunter, a professor of epidemiology and medicine at Oxford University's Nuffield Department of Population Health in the United Kingdom, wrote in an editorial that accompanied the study. Exclusion criteria included women with venous thromboembolism, history of cancer excluding nonmelanoma skin cancer, and a history of infertility treatment.
Mørch said that "knowledge is needed on the potential beneficial influence of newer contraceptives on the risk of ovarian and colorectal cancer, since evidence now relates to older types of hormonal contraceptives".
Duration of use also contributed to associated breast cancer risk.
Most breast cancers are fueled by estrogen. "It has been known that progesterone probably plays a role in breast cancer, although our research is not as mature as it is for estrogen".
The study is published today (Dec. 6) in The New England Journal of Medicine.
Lindegaard speculated that the hormones in birth control may trigger certain cells that are ready to turn into cancer, he said, given that the risk seems to increase after only a few months of use.