All cancers begin in a single organ or tissue, such as the lungs or skin. When these cancers are confined in their original organ or tissue, they are generally more treatable.

But a cancer that spreads is much more dangerous, as the organs it spreads to may be vital organs. A skin cancer, for example, might spread to the brain.

This new growth makes the cancer much more challenging to treat, as it can be difficult to find all the new tumours. If a cancer can invade different organs or tissues, it can quickly become lethal.

When cancer spreads in this way, it’s called metastasis. Metastasis is responsible for the majority (67%) of cancer deaths.

Cells are supposed to stick to surrounding tissue

Our bodies are made up of trillions of tiny cells. To keep us healthy, our bodies are constantly replacing old or damaged cells.

Each cell has a specific job and a set of instructions (DNA) that tells it what to do. However, sometimes DNA can get damaged.

This damage might change the instructions. A cell might now multiply uncontrollably, or lose a property known as adherence. This refers to how sticky a cell is, and how well it can cling to other surrounding cells and stay where it’s supposed to be.

If a cancer cell loses its adherence, it can break off from the original tumour and travel through the bloodstream or lymphatic system to almost anywhere. This is how metastasis happens.

Many of these travelling cancer cells will die, but some will settle in a new location and begin to form new cancers.

Particular cancers are more likely to metastasise to particular organs that help support their growth. Breast cancers commonly metastasise to the bones, liver, and lungs, while skin cancers like melanomas are more likely to end up in the brain and heart.

Unlike cancers which form in solid organs or tissues, blood cancers like leukaemia already move freely through the bloodstream, but can escape to settle in other organs like the liver or brain.

When do cancers metastasise?

The longer a cancer grows, the more likely it is to metastasise. If not caught early, a patient’s cancer may have metastasised even before it’s initially diagnosed.

Metastasis can also occur after cancer treatment. This happens when cancer cells are dormant during treatment – drugs may not “see” those cells. These invisible cells can remain hidden in the body, only to wake up and begin growing into a new cancer months or even years later.

For patients who already have cancer metastases at diagnosis, identifying the location of the original tumour – called the “primary site” – is important. A cancer that began in the breast but has spread to the liver will probably still behave like a breast cancer, and so will respond best to an anti-breast cancer therapy, and not anti-liver cancer therapy.

As metastases can sometimes grow faster than the original tumour, it’s not always easy to tell which tumour came first. These cancers are called “cancers of unknown primary” and are the 11th most commonly diagnosed cancers in Australia.

One way to improve the treatment of metastatic cancer is to improve our ways of detecting and identifying cancers, to ensure patients receive the most effective drugs for their cancer type.

What increases the chances of metastasis and how can it be prevented?

If left untreated, most cancers will eventually acquire the ability to metastasise.

While there are currently no interventions that specifically prevent metastasis, cancer patients who have their tumours surgically removed may also be given chemotherapy (or other drugs) to try and weed out any hidden cancer cells still floating around.

The best way to prevent metastasis is to diagnose and treat cancers early. Cancer screening initiatives such as Australia’s cervical, bowel, and breast cancer screening programs are excellent ways to detect cancers early and reduce the chances of metastasis.

New screening programs to detect cancers early are being researched for many types of cancer. Some of these are simple: CT scans of the body to look for any potential tumours, such as in England’s new lung cancer screening program.

Using artificial intelligence (AI) to help examine patient scans is also possible, which might identify new patterns that suggest a cancer is present, and improve cancer detection from these programs.

More advanced screening methods are also in development. The United States government’s Cancer Moonshot program is currently funding research into blood tests that could detect many types of cancer at early stages.

One day there might even be a RAT-type test for cancer, like there is for COVID.

Will we be able to prevent metastasis in the future?

Understanding how metastasis occurs allows us to figure out new ways to prevent it. One idea is to target dormant cancer cells and prevent them from waking up.

Directly preventing metastasis with drugs is not yet possible. But there is hope that as research efforts continue to improve cancer therapies, they will also be more effective at treating metastatic cancers.

For now, early detection is the best way to ensure a patient can beat their cancer.

Sarah Diepstraten, Senior Research Officer, Blood Cells and Blood Cancer Division, Walter and Eliza Hall Institute and John (Eddie) La Marca, Senior Resarch Officer, Walter and Eliza Hall Institute

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

Are you one of these people who loathes spending time outdoors at dusk as the weather warms and mosquitoes start biting?

Female mosquitoes need blood to develop their eggs. Even though they take a tiny amount of our blood, they can leave us with itchy red lumps that can last days. And sometimes something worse.

So why does our body react and itch after being bitten by a mosquito? And why are some people more affected than others?

What happens when a mosquito bites?

Mosquitoes are attracted to warm blooded animals, including us. They’re attracted to the carbon dioxide we exhale, our body temperatures and, most importantly, the smell of our skin.

The chemical cocktail of odours from bacteria and sweat on our skin sends out a signal to hungry mosquitoes.

Some people’s skin smells more appealing to mosquitoes, and they’re more likely to be bitten than others.

Once the mosquito has made its way to your skin, things get a little gross.

The mosquito pierces your skin with their “proboscis”, their feeding mouth part. But the proboscis isn’t a single, straight, needle-like tube. There are multiple tubes, some designed for sucking and some for spitting.

Once their mouth parts have been inserted into your skin, the mosquito will inject some saliva. This contains a mix of chemicals that gets the blood flowing better.

There has even been a suggestion that future medicines could be inspired by the anti-blood clotting properties of mosquito saliva.

It’s not the stabbing of our skin by the mosquito’s mouth parts that hurts, it’s the mozzie spit our bodies don’t like.

Are some people allergic to mosquito spit?

Once a mosquito has injected their saliva into our skin, a variety of reactions can follow. For the lucky few, nothing much happens at all.

For most people, and irrespective of the type of mosquito biting, there is some kind of reaction. Typically there is redness and swelling of the skin that appears within a few hours, but often more quickly, after just a few minutes.

Occasionally, the reaction can cause pain or discomfort. Then comes the itchiness.

Some people do suffer severe reactions to mosquito bites. It’s a condition often referred to as “skeeter syndrome” and is an allergic reaction caused by the protein in the mosquito’s saliva. This can cause large areas of swelling, blistering and fever.

The chemistry of mosquito spit hasn’t really been well studied. But it has been shown that, for those who do suffer allergic reactions to their bites, the reactions may differ depending on the type of mosquito biting.

We all probably get more tolerant of mosquito bites as we get older. Young children are certainly more likely to suffer more following mosquito bites. But as we get older, the reactions are less severe and may pass quickly without too much notice.

How best to treat the bites?

Research into treating bites has yet to provide a single easy solution.

There are many myths and home remedies about what works. But there is little scientific evidence supporting their use.

The best way to treat mosquito bites is by applying a cold pack to reduce swelling and to keep the skin clean to avoid any secondary infections. Antiseptic creams and lotions may also help.

There is some evidence that heat may alleviate some of the discomfort.

It’s particularly tough to keep young children from scratching at the bite and breaking the skin. This can form a nasty scab that may end up being worse than the bite itself.

Applying an anti-itch cream may help. If the reactions are severe, antihistamine medications may be required.

To save the scratching, stop the bites

Of course, it’s better not to be bitten by mosquitoes in the first place. Topical insect repellents are a safe, effective and affordable way to reduce mosquito bites.

Covering up with loose fitted long sleeved shirts, long pants and covered shoes also provides a physical barrier.

Mosquito coils and other devices can also assist, but should not be entirely relied on to stop bites.

There’s another important reason to avoid mosquito bites: millions of people around the world suffer from mosquito-borne diseases. More than half a million people die from malaria each year.

In Australia, Ross River virus infects more than 5,000 people every year. And in recent years, there have been cases of serious illnesses caused by Japanese encephalitis and Murray Valley encephalitis viruses.

Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of Sydney

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