Many women worry hormonal contraceptives have dangerous side-effects including increased cancer risk. But this perception is often out of proportion with the actual risks.

So, what does the research actually say about cancer risk for contraceptive users?

And is your cancer risk different if, instead of the pill, you use long-acting reversible contraceptives? These include intrauterine devices or IUDs (such as Mirena), implants under the skin (such as Implanon), and injections (such as Depo Provera).

Our new study, conducted by the University of Queensland and QIMR Berghofer Medical Research Institute and published by the Journal of the National Cancer Institute, looked at this question.

We found long-acting contraceptives seem to be as safe as the pill when it comes to cancer risk (which is good news) but not necessarily any safer than the pill.

How does the contraceptive pill affect cancer risk?

The International Agency for Research on Cancer, which compiles evidence on cancer causes, has concluded that oral contraceptives have mixed effects on cancer risk.

Using the oral contraceptive pill:

• slightly increases your risk of breast and cervical cancer in the short term, but
• substantially reduces your risk of cancers of the uterus and ovaries in the longer term.

Our earlier work showed the pill was responsible for preventing far more cancers overall than it contributed to.

In previous research we estimated that in 2010, oral contraceptive pill use prevented over 1,300 cases of endometrial and ovarian cancers in Australian women.

It also prevented almost 500 deaths from these cancers in 2013. This is a reduction of around 25% in the deaths that could have occurred that year if women hadn’t taken the pill.

In contrast, we calculated the pill may have contributed to around 15 deaths from breast cancer in 2013, which is less than 0.5% of all breast cancer deaths in that year.

What about long-acting reversible contraceptives and cancer risk?

Long-acting reversible contraceptives – which include intrauterine devices or IUDs, implants under the skin, and injections – release progesterone-like hormones.

These are very effective contraceptives that can last from a few months (injections) up to seven years (intrauterine devices).

Notably, they don’t contain the hormone oestrogen, which may be responsible for some of the side-effects of the pill (including perhaps contributing to a higher risk of breast cancer).

Use of these long-acting contraceptives has doubled over the past decade, while the use of the pill has declined. So it’s important to know whether this change could affect cancer risk for Australian women.

Our new study of more than 1 million Australian women investigated whether long-acting, reversible contraceptives affect risk of invasive cancers. We compared the results to the oral contraceptive pill.

We used de-identified health records for Australian women aged 55 and under in 2002.

Among this group, about 176,000 were diagnosed with cancer between 2004 and 2013 when the oldest women were aged 67. We compared hormonal contraceptive use among these women who got cancer to women without cancer.

We found that long-term users of all types of hormonal contraception had around a 70% lower risk of developing endometrial cancer in the years after use. In other words, the risk of developing endometrial cancer is substantially lower among women who took hormonal contraception compared to those who didn’t.

For ovarian cancer, we saw a 50% reduced risk (compared to those who took no hormonal contraception) for women who were long-term users of the hormone-containing IUD.

The risk reduction was not as marked for the implants or injections, however few long-term users of these products developed these cancers in our study.

As the risk of endometrial and ovarian cancers increases with age, it will be important to look at cancer risk in these women as they get older.

What about breast cancer risk?

Our findings suggest that the risk of breast cancer for current users of long-acting contraceptives is similar to users of the pill.

However, the contraceptive injection was only associated with an increase in breast cancer risk after five years of use and there was no longer a higher risk once women stopped using them.

Our results suggested that the risk of breast cancer also reduces after stopping use of the contraceptive implants.

We will need to follow-up the women for longer to determine whether this is also the case for the IUD.

It is worth emphasising that the breast cancer risk associated with all hormonal contraceptives is very small.

About 30 in every 100,000 women aged 20 to 39 years develop breast cancer each year, and any hormonal contraceptive use would only increase this to around 36 cases per 100,000.

What about other cancers?

Our study did not show any consistent relationships between contraceptive use and other cancers types. However, we only at looked at invasive cancers (meaning those that start at a primary site but have the potential to spread to other parts of the body).

A recent French study found that prolonged use of the contraceptive injection increased the risk of meningioma (a type of benign brain tumour).

However, meningiomas are rare, especially in young women. There are around two cases in every 100,000 in women aged 20–39, so the extra number of cases linked to contraceptive injection use was small.

The French study found the hormonal IUD did not increase meningioma risk (and they did not investigate contraceptive implants).

Benefits and side-effects

There are benefits and side-effects for all medicines, including contraceptives, but it is important to know most very serious side-effects are rare.

A conversation with your doctor about the balance of benefits and side-effects for you is always a good place to start.

Susan Jordan, Professor of Epidemiology, The University of Queensland; Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland, and Penny Webb, Distinguished Scientist, Gynaecological Cancers Group, QIMR Berghofer Medical Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What’s the difference? is a new editorial product that explains the similarities and differences between commonly confused health and medical terms, and why they matter.

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It’s the time of the year for coughs, colds and sore throats. So you might have heard people talk about having a “strep throat”.

But what is that? Is it just a bad sore throat that goes away by itself in a day or two? Should you be worried?

Here’s what we know about the similarities and differences between strep throat and a sore throat, and why they matter.

How are they similar?

It’s difficult to tell the difference between a sore throat and strep throat as they look and feel similar.

People usually have a fever, a bright red throat and sometimes painful lumps in the neck (swollen lymph nodes). A throat swab can help diagnose strep throat, but the results can take a few days.

Thankfully, both types of sore throat usually get better by themselves.

How are they different?

Most sore throats are caused by viruses such as common cold viruses, the flu (influenza virus), or the virus that causes glandular fever (Epstein-Barr virus).

These viral sore throats can occur at any age. Antibiotics don’t work against viruses so if you have a viral sore throat, you won’t get better faster if you take antibiotics. You might even have some unwanted antibiotic side-effects.

But strep throat is caused by Streptococcus pyogenes bacteria, also known as strep A. Strep throat is most common in school-aged children, but can affect other age groups. In some cases, you may need antibiotics to avoid some rare but serious complications.

In fact, the potential for complications is one key difference between a viral sore throat and strep throat.

Generally, a viral sore throat is very unlikely to cause complications (one exception is those caused by Epstein-Barr virus which has been associated with illnesses such as chronic fatigue syndrome, multiple sclerosis and certain cancers).

But strep A can cause invasive disease, a rare but serious complication. This is when bacteria living somewhere on the body (usually the skin or throat) get into another part of the body where there shouldn’t be bacteria, such as the bloodstream. This can make people extremely sick.

Invasive strep A infections and deaths have been rising in recent years around the world, especially in young children and older adults. This may be due to a number of factors such as increased social mixing at this stage of the COVID pandemic and an increase in circulating common cold viruses. But overall the reasons behind the increase in invasive strep A infections are not clear.

Another rare but serious side effect of strep A is autoimmune disease. This is when the body’s immune system makes antibodies that react against its own cells.

The most common example is rheumatic heart disease. This is when the body’s immune system damages the heart valves a few weeks or months after a strep throat or skin infection.

Around the world more than 40 million people live with rheumatic heart disease and more than 300,000 die from its complications every year, mostly in developing countries.

However, parts of Australia have some of the highest rates of rheumatic heart disease in the world. More than 5,300 Indigenous Australians live with it.

Why do some people get sicker than others?

We know strep A infections and rheumatic heart disease are more common in low socioeconomic communities where poverty and overcrowding lead to increased strep A transmission and disease.

However, we don’t fully understand why some people only get a mild infection with strep throat while others get very sick with invasive disease.

We also don’t understand why some people get rheumatic heart disease after strep A infections when most others don’t. Our research team is trying to find out.

How about a vaccine for strep A?

There is no strep A vaccine but many groups in Australia, New Zealand and worldwide are working towards one.

For instance, Murdoch Children’s Research Institute and Telethon Kids Institute have formed the Australian Strep A Vaccine Initiative to develop strep A vaccines. There’s also a global consortium working towards the same goal.

Companies such as Vaxcyte and GlaxoSmithKline have also been developing strep A vaccines.

What if I have a sore throat?

Most sore throats will get better by themselves. But if yours doesn’t get better in a few days or you have ongoing fever, see your GP.

Your GP can examine you, consider running some tests and help you decide if you need antibiotics.

Kim Davis, General paediatrician and paediatric infectious diseases specialist, Murdoch Children’s Research Institute; Alma Fulurija, Immunologist and the Australian Strep A Vaccine Initiative project lead, Telethon Kids Institute, and Myra Hardy, Postdoctoral Researcher, Infection, Immunity and Global Health, Murdoch Children’s Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.