Last week, we answered that question: when tumours grow, they compete with our healthy cells, damaging organs that we need to survive. But what happens when a tumour isn’t in a critical organ? That’s where things get interesting. I mean, that’s why we have two kidneys, right? Well, it turns out that some tumours aren’t actually immediately dangerous. So, if cells are damaged and begin to grow uncontrollably in an organ or area of the body that isn’t essential to our survival, we can actually tolerate them pretty well.

But cancers can spread, and when that happens, the stakes are dramatically raised. As cancerous cells spread, they can grow new tumours, each carrying the same damaged DNA as the first. When new tumours are established in vital organs, that’s where the real risk lies. These new growths, established by spreading cancer cells, are called secondary tumours.

Honestly, it’s wild to think about our cells wandering around, migrating throughout our bodies. And for the most part, they don't… mostly. Our cells are usually part of an entity, tied to each other and stuck in place, like in our organs. They like to hold on to each other tightly and hunker down. But sometimes the ability to move can be helpful for us! For example, if you had a little cut and it happened to get infected, your immune cells would need to migrate through your body to the cut to help fight off the infection.

It’s also a crucial part of our development. Our cells are highly mobile early throughout our growth. But in our developed bodies, those instructions are turned off, so most cells don’t move around as much. So how do they actually spread? Well, it all comes back to DNA damage.

When this happens, they can release from the tissue and start invading their surroundings. With that said, they’re not exactly fast. They can cover roughly the width of a hair in an hour. Depending on the cell, it could take them years to go from your head to your toes. But there are faster ways.

That’s exactly what happens in our bodies, too. Cancer cells can get into vessels, like the bloodstream or lymph, and can be carried throughout our bodies. To make things worse, they can leave that river almost anywhere along the way. And once they leave those vessels, we already know what can happen. New tumours, more cancer cells, more organs struggling to keep us alive.

Biologically speaking, metastasizing is really challenging for cancer cells, even if it doesn’t seem that way from the outside. Our bodies are full of ways to stop cancers from spreading, or at the very least, stall them. For starters, as they spread, they’re going to meet more and more immune cells. 

The further a cancer cell goes into the body, the more immune cells it’ll inevitably run into. Even in the bloodstream, millions of immune cells are ready to kill any cancer cells they come across. On top of that, there are other physical challenges that cancer has to overcome. Our bloodstream isn’t exactly a lazy river. For a little cancer cell, it’s like more white water rapids, fast-moving and dangerous.

We hear the word “metastasis” a lot when we talk about cancer, and for good reason. The spread of cancer dramatically increases the risks to our bodies, and because of this, it can be a major burden. But it’s also harder than it seems for cancer cells. Spreading throughout the body is a turbulent journey, full of barriers that cancer cells have to get around. But if there’s a will, there’s a way, and metastasis still happens. Because of that, researchers are using fascinating science to slow or stop the spread of cancer, making metastasis a little less intimidating. If that interests you, let me know, and we’ll do a deeper dive into new ways that cancer is being stopped in its tracks.

I hope you learned a little something today, but now it’s your turn - go spread the word.

See you next week!

If you missed last week’s letter, you can read “Let’s Talk Cancer” to learn a little more about what cancer is and how it works.