Radiotherapy is a really interesting form of cancer treatment, at least if you’re a physics nerd like me. 

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Radiotherapy is typically an adjunct to the primary treatment, meaning it is used in addition to surgery or chemotherapy. Sometimes, it is used before a surgery to shrink the tumour before removal. And sometimes, it is used after chemotherapy to give the targeted spot an extra bulldozing - to lessen the chance of relapse. 

 

Radiotherapy uses radiation to damage the DNA of cancer cells, destroying their ability to replicate and hence, they eventually die. But what is radiation specifically? Radiotherapy uses ionised particles and directs them towards a target - think of a cross between a sniper and a machine gun - spraying tiny bullets at the tumour, ripping up the scaffolding. 

 

“Ionised particles” you ask? Or maybe you didn’t ask…I’m telling you anyway. 

An ionised particle is simply a small thing at the level of an atom that holds a charge. Remember learning about positives and negatives and how they attract in school? Yeah, those things. 

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Our body is full of charged particles, or ions. 

Na+ (sodium) is an example of an anion (positively charged ion).

K- (potassium) is an example of a cation (negatively charged ion). 

For instance, our nerves work by allowing ions to move across the cell membrane in a Mexican wave-like fashion. 

 

Radiotherapy involves the use of radioactive substances to produce high level of ions and directs them at the cancer cells.

 

There are a few different types of radiation used, depending on the depth/type of cancer targeted. 

 

Electrons are small, negatively charged ions that don’t carry much energy. As such, they don’t penetrate very deeply. They are used when the target is superficial (such as a lymph node near the surface). That way, the tissue beneath won’t be as affected. Imagine these as BB gun pellets. 

 

Protons are bigger, positively charged ions. Interestingly, they don’t tend to lose energy until a bit deeper in the body. These particles are good at impacting deep tumours without causing much damage to the tissue it passes through. Imagine them as a rolling grenade. 

 

The most commonly used particles used in radiotherapy are photons (light particles). To confuse you further, photons have no charge and no mass. They’re like ghosts bullets, able to pass through the entire body and out the other side. They cause damage to the cancer cells with energy received from speeding them up to a blindingly fast rate through a linear accelerator. 

 

Photons are used in a typical X-ray. However, in radiotherapy, the x-ray waves are targeted through a narrow window rather than your whole chest. 

 

Your oncologist will warn you about the drawbacks of the therapy before commencement. These include burns, hair loss, nausea, etc. Radiotherapy will often cause tissue swelling, which becomes especially problematic when the brain is involved.

This is why patients with brain tumours will be given high dose steroids to combat the issue. 

 

We hope your brain isn’t too swollen after reading all that physics gobble-de-gook.