A new study suggests that the use of progestogen-only hormonal contraceptives is associated with a higher risk of breast cancer.
“Current or recent use of progestogen-only birth control is associated with a small increase in breast cancer risk,” the University of Oxford researchers concluded, which is of the same magnitude as with combined hormonal contraceptives.
However, they emphasize that excessive risks “need to be considered in the context of the demonstrated benefit of using contraceptives in a woman’s reproductive years.”
Previous studies have shown that the use of combined estrogen and progestin birth control pills is associated with a small increase in breast cancer risk, which declines when the use is stopped.
Kirstin Peary, one of the lead authors at Oxford Population Health, said the overall risk is lower for younger women.
She explained: “Because the underlying risk of developing breast cancer in a person increases with age, the absolute excess risk of breast cancer associated with any type of oral contraceptive is lower in women who use it at a younger age.”
Claire Knight of Cancer Research UK, who funded the study, said: “Progestogen-only combined hormonal contraceptives may increase the risk of breast cancer, but the risk is small.
“Women who use contraceptives most often are younger than 50, when the risk of breast cancer is even lower.
“For those looking to reduce their risk of cancer, quitting smoking, eating a healthy, balanced diet, drinking less alcohol and maintaining a healthy weight are of the utmost importance.
“There are many potential benefits of using birth control, as well as other non-cancer risks. Therefore, the decision to take them is a personal choice and should be made in consultation with your doctor so that you can make the decision that is right for you.
What did the study give?
Scientists studied NHS records of 10,000 women under the age of 50 who were diagnosed with breast cancer between 1996 and 2017.
Their medical history was compared with a control group of 18,000 women of the same age from the same primary care practice who had not been diagnosed with the disease.
How high is the risk?
A 25 percent increase in risk corresponds to 61 women aged 25 to 29 for every 100,000 diagnosed cases of breast cancer over a 15-year period. During the same period, those aged 35 to 39 had an increased risk of 265 women per 100,000 people.
However, the researchers said the findings do not mean women should stop using hormonal birth control pills.
Professor Reeves said: “I suspect that if women have historically been willing to take this risk in exchange for the many benefits of taking hormonal contraceptives, they may continue to do so.”
Cancer experts have found that women who use contraceptives most often tend to be younger than 50, when the risk of breast cancer is lower and other factors such as exercise, smoking and drinking are more likely to play a role.
Gillian Reeves, professor of statistical epidemiology and director of the Department of Cancer Epidemiology at the University of Oxford, said: “I don’t see any indication here that women need to necessarily change what they do.”
She added: “Yes, there is an increase here, and yes, no one wants to hear that what they are taking increases their risk of breast cancer by 25 percent.
“The main goal of this study was to fill a knowledge gap.
“We have known for many years that combined oral contraceptives, which women have been using for decades, also affect breast cancer risk, a small increase in risk that is temporary.
“We weren’t completely sure what the equivalent effect of these progestogen-only birth control would be.
“We have shown that they are exactly the same in terms of breast cancer risk, they seem to have a similar effect to other contraceptives, and an effect that we have known for many years.
“I suspect that if women in the past had been willing to take this risk in exchange for the many benefits of taking hormonal contraceptives, they might have been willing to continue doing so.”
Analysis I Health Editor Paul Gallagher
Birth control pills were already known to slightly increase the risk of breast cancer (and reduce the risk of ovarian and uterine cancer), but a new study shows that the risks are the same regardless of the type of pill used.
Researchers have shown that oral contraceptives are associated with a small but significant increase in breast cancer risk and that progestogen-only contraceptives have similar effects to combined contraceptives. Previous studies had very little data on progestogen-only contraceptives and breast cancer risk, but due to their growing popularity (they now account for half of prescriptions), this is no longer the case.
Women have previously accepted the risks associated with estrogen-progestin combined contraceptives, so the authors expect this to remain as more is known about progestin-only pills. And, as with combination pills, the risk decreases when women stop using birth control.
One limitation of the study is that it did not take into account which hormonal birth control the women used in the past or how long they used progestogen-only birth control. It also didn’t matter if family history contributed to her risk level, which prompted Breast Cancer to now call for more research to fully understand the implications of using this type of birth control.
Although the results suggest a short-term association between hormonal contraceptive use and breast cancer risk, the researchers caution that they do not provide information on long-term associations or the effect of total duration of contraceptive use on breast cancer risk.
Studies show that the use of progestogen-only contraceptives has increased significantly in recent years, but information about their association with breast cancer risk is limited.
In 2020, nearly as many prescriptions for progestogen-only oral contraceptives were filled in England as for combination pills.
The researchers analyzed data from 9,498 women who developed invasive breast cancer between the ages of 20 and 49 and 18,171 women who did not have breast cancer.
Data was collected from the Clinical Practice Research Data Channel (CPRD).
About 44 percent of women with breast cancer and 39 percent of women without breast cancer who took part in the study received a prescription for hormonal birth control an average of three years before diagnosis.
About half of these women were last prescribed progestogen-only birth control.
The researchers combined the results of the CPRD on oral contraceptive use with those of other previously published studies to estimate the absolute additional risks.
The scientists note that their study, published in Plos Medicine, did not provide any information about long-term links between hormonal contraceptives and breast cancer risk.
The study was funded by core funding provided by Cancer Research UK’s Cancer Epidemiology Unit.
Dr. Kotrina Temchinaite, head of scientific communications at Breast Cancer Now, said: “With both types of birth control, this excess breast cancer risk decreases over time when you stop using them.
“The study did not look at what hormonal birth control the women used in the past or how long they used progestogen-only birth control.
“It also didn’t matter if her family medical history contributed to her risk. Therefore, more work is needed to help us fully understand the implications of using this type of birth control.
“Breast cancer is rare in young women. A slight increase in risk when taking hormonal contraceptives means that several more cases of the disease are diagnosed.
Additional Press Association coverage
Source: I News
I’m Raymond Molina, a professional writer and journalist with over 5 years of experience in the media industry. I currently work for 24 News Reporters, where I write for the health section of their news website. In my role, I am responsible for researching and writing stories on current health trends and issues. My articles are often seen as thought-provoking pieces that provide valuable insight into the state of society’s wellbeing.