Why does radiotherapy take so many sessions?
Why the radiation is not given all at once, why sessions run back to back, and why the number differs for each person.
Travelling every day is tiring, especially from another city. It is natural to ask why it cannot all be given at once.
Radiation does not work at once
Radiation damages the DNA of cells, and this damage builds up over days and weeks. Cancer cells do not die at once either; they keep dying for weeks or months after treatment ends.
Healthy tissue needs time to repair
When the total dose is split into smaller parts with gaps between them, cells have time to repair. Splitting the dose this way means less harm to healthy cells while the effect of treatment remains. Each part is called a fraction.
How is the number decided?
The doctor sets the dose, number of sessions and method from the type of cancer, the planning results, tests, and research on that cancer and that area. So your schedule may differ from that of a patient you met in the waiting room.
- A common schedule: every working day for several weeks
- Fewer sessions with a larger dose: in some cancers
- Focused treatment: for small tumours, up to about five sessions
- Treatment to ease symptoms: sometimes a single session
More sessions do not mean the disease is worse.
If you cannot make a session
Tell the treatment centre early. Do not change the schedule yourself or put a session off. Your care team decides how to continue.