52 / 2063
9/16/17
7
ESTRO
2017
The “x” Rs of Radiotherapy
• Radiosensitivity
• Repair
• Repopulation
• Redistribution
• Reoxygenation
• iRradiated volume
• Restoration (long term recovery)
• Re-iRRadiation
• another “R” still to be invented…
ESTRO
2017
“Typical” dose per fraction
• 1.8-2 Gy for standard
fractionation
• 1.1-1.3 Gy for hyper-
fractionation
Fractionation sensitivity
Withers et al, 1983