56. RADIOTHERAPY: THE 4 R'S OF FRACTIONATION Flashcards
- What are the 4 R’s of Fractionation?
- Repair
- Redistribution
- Re-Oxygenation
- Repopulation
- What is Repair?
- this happens every few hours
- the cells are allowed to repair sub-lethal damage
- What is Redistribution?
- this happens every few hours to days
- the cell is given time to move to a more radiation
sensitive phase of the cell cycle
- What is Re-Oxygenation?
- this happens every few hours to days
- the tumour will undergo hypoxia
- the tumour will resist the radiation more
- What is Hypoxia?
- this is when the tumour does not have enough oxygen
available to maintain homeostasis - this happens at the tissue level
- it makes the tissue more sensitive
- What is Repopulation?
- this happens every few weeks
- healthy and malignant cells will repopulate
- this happens after irradiation
- List the 4 Fractionation Schemes.
- Conventional
- Hyper-Fractionation
- Accelerated Fractionation
- Hypo-Fractionation
- When it comes to Conventional Fractionation,
what is the:
8.1. Dose per fraction
8.2. Fractions per week
8.3. Total dose
8.4. Issues
(8.1) 1.8 to 2.2 Gy
(8.2) Five
(8.3) 45 to 50.4 Gy
(8.4) - it can be too slow for the fast growing tumours
- the dose is too low for resistant cancers
- When it comes to Hyper- Fractionation,
what is the:
9.1. Dose per fraction
9.2. Fractions per week
9.3. Total dose
9.4. Issues
9.5. In which circumstance it is used
(9.1) 1.1 to 1.3 Gy
(9.2) Ten
- these treatments are given more than once a day
(9.3) 70 to 80 Gy
(9.4) - it is a burden on patients and staff
- it is a burden on the equipment
- no clear benefit has been demonstrated
(9.5) - it is used to avoid late complications of the normal
tissue
- When it comes to Accelerated Fractionation,
what is the:
10.1. Dose per fraction
10.2. Fractions per week
10.3. Total dose
10.4. Issues
10.5. In which circumstance it is used
(10.1) 1.4 to 2.5 Gy
(10.2) Ten
- these treatments are given more than once a day
(10.3) 40 to 50 Gy
(10.4) - it is a burden on patients and staff
- it is a burden on the equipment
- it has acute reactions
- the total dose is delivered for a shorter period of
time
(10.5) - it is used for fast growing tumours
- When it comes to Hypo- Fractionation,
what is the:
11.1. Dose per fraction
11.2. Fractions per week
11.3. Total dose
11.4. Issues
11.5. In which circumstance it is used
(11.1) above 2.5 Gy
(11.2) 1 to 5
(11.3) 20 to 55 Gy
(11.4) - it has acute reactions
- the total dose is delivered for a shorter period of
time
(11.5) - it is used for highly conformal treatments
- Does this example of Conventional Fractionation make sense?
- yes
- Does this example of Accelerated Fractionation make sense?
- yes
