How many radiation therapy sessions, and how long treatment lasts

The short answer

For curative treatment, external beam radiation therapy usually means 25-30 sessions, one a day, Monday to Friday, over a period of 5-6 weeks. The exact number is set by your radiation oncologist, depending on the type of cancer, the area being treated, and the goal of treatment — curative or palliative.

Radiation therapy works through small doses, repeated daily, so that the healthy tissue around the area has time to recover between sessions. The total dose needed is split over several days — that is why the daily doses are called "fractions". The higher the total dose or the more sensitive the area, the more fractions there are and the longer the treatment.

Palliative treatments, which mainly aim to control symptoms, usually have far fewer sessions — sometimes just one or a few. Curative treatments, which aim to eliminate the disease, usually follow the 25-30 session schedule described above.

Sessions take place Monday to Friday, with a break at the weekend — the body needs that time to recover. A single session usually takes 15-30 minutes, and only a few minutes of that is actual radiation; the rest is positioning and checks.

For most curative schedules, this means a daily commute to the clinic for 5-6 weeks in a row — which is why it is worth thinking early about how to organize transport and your schedule, not just the treatment itself.

• a medical break, if a reaction occurs that calls for one;
• adjustments to the plan, decided by the medical team depending on how things progress;
• the type of machine and the technique used, which can influence the number of fractions for the same total dose;
• the fractionation approach chosen — some modern curative treatments use higher doses per session and a much smaller number of sessions (for example for breast or prostate cancer), over a shorter period.

None of these is something the patient controls or needs to anticipate — they are clinical decisions, made by the team along the way.

• How many sessions are planned for my case, and over what period?
• Is the treatment curative or palliative — and what does that mean for the number of sessions?
• Are the sessions every working day, or are there fixed days off?
• What happens if I have to miss a day?

Once you know the number of sessions and the start date, add them one by one to the appointments calendar as you receive them — each appointment can be exported as an .ics file, with an alarm one day before. It helps to know from the start, even roughly, how long the daily commute will last, so you can organize transport in good time.