Fighting Cancer with Stardust - A brief history of Brachytherapy

This is a story of thermonuclear explosions, mass extinctions and hope. Maybe not what you expected from someone talking about cancer treatments. But here it goes. And it makes sense.

It all started with a bang (one of many, in this story), but no one heard the sound because there was no sound propagating in space, and because, in fact, there was not even space. Or anyone there to listen. Energy splashing out of one singularity, creating space and time as it expands: the Big Bang, the beginning of the universe. Laws of physics were already there, and you will be surprised to know that the later events — just like in a Netflix series — were already written in those first moments: including asteroids, the extinction of the dinosaurs, and life-saving brachytherapy.

As the universe expanded, things cooled down and the first atomic nuclei could form. Hydrogen, mostly. Some helium. Not much more.

Gravitation, not a dating app

Gravitation — more than loneliness or some dating app — made these primordial atoms cluster into clouds and eventually bump into each other. As things got hotter and denser, the universe witnessed the birth of the first stars. Here, under immense pressure and heat, simple atoms fused together to create heavier elements (carbon, oxygen, all the way to iron). And then, when the heaviest of the ancient stars ran out of fuel (feels a bit like Tolkien, doesn’t it?), they exploded as spectacular supernovas, generating and blasting even heavier elements—such as gold, silver, mercury, and uranium—out into space.

Spoiler: Our Sun will not blast into a supernova because its mass is below the limit that allows such an event—which, for the curious, is called the Chandrasekhar limit, and it corresponds to 1.4 times the Sun's mass.

History was repeating itself — just richer.

The dust from the explosion of those first ancient stars gathered into swirling clouds around new stars. But this time, the clouds were richer in elements—not just the simple atoms of hydrogen and helium. Over a very long (very loooong) time, these dusty disks clumped together to form planets. Our Earth was one of them.

Most of the heavy metals on Earth sank deep below the surface, leaving only tiny traces of rare stuff like iridium near the top. So, when geologists found more iridium than usual in a layer of Earth’s rock, they knew something big must have happened—like a cosmic visitor from space. (No, not E.T.—though that would have been cool too.)

Another bang, and the dinosaurs heard it loud.

This time, there was someone to hear the bang. And I bet it was terrifying.

About 66 million years ago, a giant asteroid slammed into Earth. The impact kicked up dust and blocked out sunlight for days, months, even years. The dinosaurs, who had ruled the planet for millions of years, didn’t make it through this event (well, except for birds, but that’s another story).

What’s surprising — and the connection to brachytherapy in this tale of stars and cosmic explosions — is what geologists found in the rock layers marking that moment in Earth’s crust: a lot of iridium, an element otherwise nearly absent on our planet. Why? Because that asteroid brought it with it, sprinkling it into Earth’s crust (like Parmigiano cheese on pasta... you know, I’m Italian).

Without that asteroid, maybe dinosaurs would still be here, and humans wouldn’t. Most importantly, without that asteroid, we wouldn’t have the iridium we use today to deliver life-saving brachytherapy treatments.

In every story, there is always place for Marie Sk?odowska Curie

Fast forward a few million years, and humans learned how to use tools and dig metals out of the Earth. Fast forward again, and scientists like Marie Sk?odowska Curie uncovered the secrets of radioactivity (and, in doing so, opened the door to understanding how elements were formed in burning and exploding stars).

As our understanding of radiation and medicine grew, scientists realized that if they could bring a tiny source of radiation right inside a tumor, they could destroy cancer cells more directly while protecting the healthy tissue around them. This idea is called brachytherapy.

So, what’s the perfect material for such a treatment? It needs to be strong enough, chemically stable, have a reasonable half-life, and emit radiation at just the right energy. Luckily for us, that asteroid 66 million years ago brought exactly what we needed: iridium.

Side dish: The asteroid, however, wasn’t like a food delivery service bringing warm (well… not always warm) pizza or noodles to your door. It was more like one of those food trucks delivering frozen food. The iridium it delivered — called iridium-191 — needs to be “warmed up” before it can be used. And our microwave? A nuclear reactor.

Saving lives of women in low- and middle-income countries. And beyond.

Brachytherapy is a form of internal radiation therapy where a tiny radioactive source is placed inside or near a tumor, delivering targeted treatment while sparing surrounding healthy tissue. It is commonly used to treat cancers like cervical, prostate, breast, and head and neck cancers.

In low- and middle-income countries, brachytherapy plays a critical role, especially in treating cervical cancer, which remains one of the leading causes of cancer-related deaths among women. With its precision, effectiveness, and relatively low infrastructure requirements, brachytherapy is a key tool for expanding access to cancer care in regions where resources are limited.

By bringing this treatment to these areas, brachytherapy saves countless women's lives, offering hope where it is needed most and reducing the global burden of cancer in vulnerable communities.

What a crazy story, right?

So, what a journey: from the Big Bang, to ancient stars exploding in magnificent supernovae, to planets forming, and then an asteroid crashing into Earth—wiping out the dinosaurs while delivering iridium to our planet. Millions of years later, we humans learned how to charge that iridium in a nuclear reactor and use it to save lives through brachytherapy.

That’s quite a story, don’t you agree?

Read more

Read more about projects addressing women's health in low and medium income countries

• Fighting cervical cancer in Rwanda (Elekta Foundation)
• Accurately targeting women’s cancers in Mongolia | IAEA

About me

I’m passionate about radiation and radiation safety, and I lead these efforts at a top MedTech company. My experience includes working with the European Commission and international physics laboratories, where I developed my expertise in nuclear physics (without causing any explosions!). With a PhD in applied nuclear physics, I’ve published research in peer-reviewed journals and enjoy crafting content that makes complex topics in science, safety, and security accessible and engaging—because everyone loves a good science story!

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