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Asked by Adil to Jen on 14 Mar 2016.
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Jen Lowe answered on 14 Mar 2016:
Adil – a very relevant question. When we create a plan for each patient we have to deliver the prescribed amount of radiation to the cancer, but also make sure that the rest of the body will be ok. The Dr. outlines (on the CT scan onscreen) the organs at risk (OAR) and gives us dose limits for each of them. So, healthy cells do get damaged but we ensure that they receive no more dose than the Dr. thinks will be safe. The damage to the rest of the body is what gives you the side effects like sore red skin, diarrhoea, hair loss.
“Cancer cells tend to divide quickly and grow out of control. Radiation therapy kills cancer cells that are dividing, but it also affects dividing cells of normal tissues. The damage to normal cells causes unwanted side effects. Radiation therapy is always a balance between destroying the cancer cells and minimizing damage to the normal cells.”
So, yes the radiation does damage the rest of the body, but we aim to make it manageable and manage the balance between risk (injury/side effects v. benefit (cure).
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Comments
Greg commented on :
What Jen said. A lot of the developments in radiotherapy (such as IMRT or VMAT) have been machines that can basically deliver more complicated dose patterns, from all angles. That means that the cancer is the part of the body that gets by far the most radiation, so although the rest of the body is damaged, the cancer is the only part that is actually killed.
If you’ve seen stuff about proton therapy in the news, this is also why it is an exciting new therapy. Different particles deposit energy at different depths (Google ‘Bragg curve’ to see what I mean). Protons have a different Bragg curve to the photons and electrons that are currently used, which means they can treat some cancers without causing as much damage to the surrounding tissue.