COPENHAGEN, Dec 7 — Newer birth control drugs developed to replace those tied to cancer risk were thought to improve safety for the women who took them. It turns out they didn’t, according to a massive new study.
While contraceptive drugs that contain oestrogen have long been suspected of increasing the likelihood of breast cancer, researchers had expected smaller doses of the hormone, often combined with the drug progestin, would be safer, said Lina Morch, an epidemiologist at Copenhagen University Hospital who led a study analysing the records of 1.8 million women in Denmark.
The study’s results, published yesterday in the New England Journal of Medicine, show not only that the danger persists in the newer formulations, but that it was also seen in other hormonal contraceptive drugs, including intrauterine devices that use progestin only.
“We had hoped that one of the products would be a better alternative,” she said in an interview. “Unfortunately, none of these products are risk-free.”
The overall increase in breast cancer risk was relatively small, about 20 per cent higher among current and recent users of oral contraceptives than among those who never used the drugs. The rate, similar to that among women who took older versions, translates to about one extra case of breast cancer among every 7,690 women taking the drugs, the researchers said.
Despite the risk, women will continue to use the pharmaceuticals, Morch said. What they should know, however, is that the longer they take them, the greater the chance they will develop breast cancer. And for those who take the drugs for five years or more, the risk will persist for as long as five years after they stop, she said. (Hormonal contraceptives also increase the risk of cardiovascular disease, she noted.)
“There was some optimism regarding the development of a formulation that would reduce a woman’s risk of breast cancer”
Those dangers are somewhat offset by reduced risks of cancer — of the ovaries, endometrium, and digestive system — that other studies have linked to birth control pills, according to David Hunter, an Oxford University epidemiologist who wrote a commentary on the study. Still, the data show that the search for birth control drugs that don’t increase breast cancer risk must continue, he said.
“In the 1980s and 1990s, there was some optimism regarding the development of a formulation that would reduce a woman’s risk of breast cancer,” he said in the commentary, “but research into this possibility appears to have stalled.”
Morch’s team pored through years of electronic health records collected by the Danish health system, using prescription data to identify which women had taken the drugs and then track their health outcomes. Traditionally, such studies have involved recruiting thousands of patients, tracking them as their lives take new turns through new jobs and home addresses, sending questionnaires, and sometimes telephoning them. Researchers using the approach often lose contact with some patients, and conducting such studies often cost “a fortune,” Morch said.
But by using computer databases from national health systems, which in Denmark are comprehensive, researchers can look at years of patient data far more cheaply, and with no risk of losing contact.
The data are “a gold mine for doing these kinds of analyses,” she said. “It’s almost unethical not to do this kind of analysis on data that’s already there, and it’s for the benefit of women and people in general to do it.”
For now, Morch said, even with the newer pharmaceuticals, women whose families have a strong history of breast cancer or heart disease may want to consider using other methods of birth control, such as employing condoms or spermicidal devices. — Bloomberg