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.

Have you ever tried to bring back fond memories by eating or drinking something unique to that time and place?

It could be a Pina Colada that recalls an island holiday? Or a steaming bowl of pho just like the one you had in Vietnam? Perhaps eating a favourite dish reminds you of a lost loved one – like the sticky date pudding Nanna used to make?

If you have, you have tapped into food-evoked nostalgia.

As researchers, we are exploring how eating and drinking certain things from your past may be important for your mood and mental health.

Bittersweet longing

First named in 1688 by Swiss medical student, Johannes Hoffer, nostalgia is that bittersweet, sentimental longing for the past. It is experienced universally across different cultures and lifespans from childhood into older age.

But nostalgia does not just involve positive or happy memories – we can also experience nostalgia for sad and unhappy moments in our lives.

In the short and long term, nostalgia can positively impact our health by improving mood and wellbeing, fostering social connection and increasing quality of life. It can also trigger feelings of loneliness or meaninglessness.

We can use nostalgia to turn around a negative mood or enhance our sense of self, meaning and positivity.

Research suggests nostalgia alters activity in the brain regions associated with reward processing – the same areas involved when we seek and receive things we like. This could explain the positive feelings it can bring.

Nostalgia can also increase feelings of loneliness and sadness, particularly if the memories highlight dissatisfaction, grieving, loss, or wistful feelings for the past. This is likely due to activation of brain areas such as the amygdala, responsible for processing emotions and the prefrontal cortex that helps us integrate feelings and memories and regulate emotion.

How to get back there

There are several ways we can trigger or tap into nostalgia.

Conversations with family and friends who have shared experiences, unique objects like photos, and smells can transport us back to old times or places. So can a favourite song or old TV show, reunions with former classmates, even social media posts and anniversaries.

What we eat and drink can trigger food-evoked nostalgia. For instance, when we think of something as “comfort food”, there are likely elements of nostalgia at play.

Foods you found comforting as a child can evoke memories of being cared for and nurtured by loved ones. The form of these foods and the stories we tell about them may have been handed down through generations.

Food-evoked nostalgia can be very powerful because it engages multiple senses: taste, smell, texture, sight and sound. The sense of smell is closely linked to the limbic system in the brain responsible for emotion and memory making food-related memories particularly vivid and emotionally charged.

But, food-evoked nostalgia can also give rise to negative memories, such as of being forced to eat a certain vegetable you disliked as a child, or a food eaten during a sad moment like a loved ones funeral. Understanding why these foods evoke negative memories could help us process and overcome some of our adult food aversions. Encountering these foods in a positive light may help us reframe the memory associated with them.

What people told us about food and nostalgia

Recently we interviewed eight Australians and asked them about their experiences with food-evoked nostalgia and the influence on their mood. We wanted to find out whether they experienced food-evoked nostalgia and if so, what foods triggered pleasant and unpleasant memories and feelings for them.

They reported they could use foods that were linked to times in their past to manipulate and influence their mood. Common foods they described as particularly nostalgia triggering were homemade meals, foods from school camp, cultural and ethnic foods, childhood favourites, comfort foods, special treats and snacks they were allowed as children, and holiday or celebration foods. One participant commented:

I guess part of this nostalgia is maybe […] The healing qualities that food has in mental wellbeing. I think food heals for us.

Another explained

I feel really happy, and I guess fortunate to have these kinds of foods that I can turn to, and they have these memories, and I love the feeling of nostalgia and reminiscing and things that remind me of good times.

Understanding food-evoked nostalgia is valuable because it provides us with an insight into how our sensory experiences and emotions intertwine with our memories and identity. While we know a lot about how food triggers nostalgic memories, there is still much to learn about the specific brain areas involved and the differences in food-evoked nostalgia in different cultures.

In the future we may be able to use the science behind food-evoked nostalgia to help people experiencing dementia to tap into lost memories or in psychological therapy to help people reframe negative experiences.

So, if you are ever feeling a little down and want to improve your mood, consider turning to one of your favourite comfort foods that remind you of home, your loved ones or a holiday long ago. Transporting yourself back to those times could help turn things around.

Megan Lee, Senior Teaching Fellow, Psychology, Bond University; Doug Angus, Assistant Professor of Psychology, Bond University, and Kate Simpson, Sessional academic, Bond University

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