One of the first studies to look at links between progestogen-only contraception and a woman's odds of developing breast cancer has identified a slight increased risk associated with using the birth control.
But the study, published in PLOS Medicine journal, states any higher risk must be viewed in the context of the well-established benefits of contraceptive use in women’s reproductive years.
Researchers examined data from over 9-thousand women in the United Kingdom who developed invasive breast cancer between the ages 20 and 49, and more than 18-thousand closely matched women without breast cancer.
According to the study, women taking progestogen-only contraceptives, and those who have recently stopped using them, are at a 20 to 30 per cent higher risk of developing breast cancer.
The rate is similar to that seen in women who take combined oral contraceptives, which use both estrogen and progestogen - this type of birth control has been much more extensively studied.
The Medical Director at Family Planning Australia, Dr Clare Boerma, says while the 20 to 30 per cent risk may be technically correct, it can also be misleading when it comes to the real risk.
"Relative risk is looking at how your risk changes, but what we really need to focus on is our absolute risk. And when the absolute risk of something is very small, so say our chance of getting breast cancer overall, even if your risk goes up with a medication of 20 to 30 per cent, your absolute numbers of your chance of getting that outcome is still a small risk. So it's important to keep in mind that the relative risk, and it can sound potentially more alarming than what the actual chance to your risk would be personally."
The small heightened risk identified mainly affects older users of progestogen-only contraceptives.
Use of this type of birth control has been increasing in Australia, in part because it can suit some women who don't tolerate combined oral contraception.
