The difference between charged particles and photons is that charged particles deposit most of their energy at the end of their range.

Basically, most of the treatments with radiotherapy use X-rays which is like light; light is attenuated in depth so you have a high dose on the skin and then it gradually decreases in the body.

Using protons or carbon ions you have a low dose in the skin and then when they reach the tumour they release most of their energy.

So that’s a big advantage in terms of conformality and in terms of sparing normal tissue because then you can irradiate only from a few angles and spare a lot of normal tissue.

What are you discussing at ESTRO?

The talk was about the radiobiology of particles.

So the point is that there is this physical difference between photons and charged particles which is very important but there is also a biological difference.

So at the end, when these particles release most of their energy in the tumour, then you have a different biological effect.

This helps in killing radio-resistant tumours or very hypoxic tumours.

So we have shown today that there is a lot of research on-going on the use of different ions, for example, using not only protons and carbon but also helium or oxygen, depending on the kind of tumour that you can use.

Will you be able to overcome hypoxia?

The idea is exactly this one.

The idea is that when you make this kind of damage with particles, being hypoxic doesn’t help.

So, let’s say, at the moment the tumours live in hypoxia and when you are in hypoxia you don’t create these free radicals that are very important for X-rays.

When you go with the ions it’s like smashing directly the DNA so you don’t need oxygen around, you just smash your tumour and you don’t care about hypoxia.

It’s a little bit like, if I can say, a little bit like... I generally explain it this way: I have a daughter and when I go into a candy shop with my daughter at the beginning she doesn’t make a lot of damage.

I kind of run quickly and she tries to take something but I’m very fast.

But gradually she starts to take candies and candies and candies and then at the end she’s slow and when she’s slow she can easily grab things.

Imagine now electrons, I’m ionising electrons, the same thing with my daughter and the candies.

Then at the end she’s full of candy, my money is over and she stops.

That’s the brag pick, it’s what we call the brag pick at the end.

This brag pick at the end, of course when you are slow so you can grab all the electrons around, you are very effective and the damage that you create is almost impossible to repair.

Are carbon ions less toxic?

This is exactly because they have this advantage of giving then a low dose in the entrance.

Now imagine my daughter again; the entrance of the shop is the normal tissue and then you are very fast because these carbon ions are accelerated at very high energy.

So they enter in the body; at the beginning they release a little energy.

It’s like my daughter running – she has no time to grab. So the damage to normal tissue is low but when you are in the tumour, now you have slowed down and now you look around and you create a lot of damage.

So the damage to normal tissue will be small and the damage to the tumour will be high.

If you use light, if you put something in front of the light you immediately attenuate the light so the dose to the skin will be higher than the dose to the tumour.

Angiogenesis is said to be effective, what is the biology behind it?

This is a fascinating field.

In a way it’s old; it is known that radiation causes vascular damage, let’s say, this is very well known since 1930 or so.

But these days it’s coming back because the idea is that when you go to hyperfractionation, hyperfractionation means very high dose in very few fractions,
then it looks like you can damage not really the single cells but the stroma, the microenvironment of the tumour.

So you basically imagine that you can destroy all the vasculature that goes into the tumour; the tumour will die anyway by starvation.

So you don’t need to kill every single cell.

This is very interesting, very controversial, because this seems to work in a way but, on the other hand, looks like the tumours are smart enough that they can recreate new vessels and then they are back in shape after some time.

But it’s a wonderful research topic, I think, and there is a lot of research going on in this field.