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3
Introduction
•
Factors influencing decision on how to retreat
•
Previous dose/fractionation and volume irradiated
•
Organs at risk eg. spinal cord
•
Time from the first treatment
•
Local disease or metastases
•
Curative or palliative intent
•
Alternatives to reirradiation
5
Introduction
•
Changes in normal tissue tolerance with time
6
Isoeffective dose (Gy)
Time interval (days)
recovery kinetics
repopulation long-term
restoration
spinal cord
oral mucosa
160
140
120
100
80
60
40
20
0 0.00001 0.0001 0.001 0.01 0.1
1
10
100
Long-term recovery
from radiation injury
in some tissues
(not all!)
Basic Clinical Radiobiology, 4th Ed, page 150