• Question: How does radiotherapy work?

    Asked by seen520cots to williamtolmie, martinpike, Jen, Lini, Erminia, emily_s, eirinbeese, charlotteslade, Charlotte, Ana on 20 Jun 2025.
    • Photo: Martin Pike

      Martin Pike answered on 20 Jun 2025:

      Cancer cells reproduce rapidly and so are more likely to suffer or die when exposed to radiation. Radiotherapy is about giving a dose of radiation high enough and localised enough to kill a cancer without damaging the surrounding normal tissues too much. It does however have side-effects, some of which can be long-lasting.

    • Photo: Charlotte Heaven

      Charlotte Heaven answered on 23 Jun 2025:

      When we expose cells to radiation such as x-rays, protons or carbons the radiation releases energy which damages the DNA in our cells.
      Our DNA is basically a long string of different molecules held together by bonds (kind of like a line of people all holding hands), the radiation pumps so much energy into those bonds that they break, causes a break in the chain of DNA (think of this like being in a busy crowd and the chain of holding hands gets bumped and pushed until one person has to let go).
      DNA has two strands and if the radiation only breaks one of the strands then it is usually OK for the body to repair (a bit like if two people hold hands and let go of one hand, you will probably be able to get back to each other), but if it breaks both strands of DNA (we call this a double strand break) then the body struggles to repair the break and the cell can die.
      In radiotherapy we aim beams of radiation at the tumour, causing lots of these double strand breaks so that the cancer cells cannot repair them and die.

    • Photo: Charlotte Slade

      Charlotte Slade answered on 1 Jul 2025:

      This is one of the most important questions a scientist can answer, because it’s about how we use clever physics to help people in a very direct and powerful way.

      Imagine your body is a beautiful, busy garden. Most of it is filled with healthy “flower” cells, all working together perfectly. Sometimes, a few “weed” cells (cancer cells) start to grow. These weeds grow too fast and can get in the way of the healthy flowers. We need a way to remove just the weeds, without hurting the rest of the garden.

      Radiotherapy is like using a very special, incredibly precise tool to get rid of those weeds.

      Instead of pulling them by hand, scientists and doctors use focused beams of energy, a bit like a super-powered magnifying glass focusing a beam of sunlight. These beams are aimed with pinpoint accuracy, right at the weeds.

      This beam of energy is specially designed to damage the fast-growing weeds much more than the healthy flowers around them. The healthy flower cells are stronger and better at repairing themselves if they get a little bit of splash from the energy beam, but the weaker weed cells can’t.

      So, by aiming these clever beams from different directions all to meet at one point, doctors can target the weeds and give them a dose of energy that stops them from growing, while keeping the rest of the garden as safe as possible.

      It’s a brilliant example of how physicists, engineers, and doctors all work together, using their understanding of energy to create tools that can heal people.

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