Hall 24 - Retreatment after RT: Possibilities & Perils

Question 1

What are key considerations for re-irradiation?

Answer 1

• Dose and volume of initial RT with overlap extent
• Prior chemo
• Time since prior RT
• Tissues/OARs
• Use of highly conformal techniques
• Alternative options (surgery)

Question 2

What kinds of tissues recover better to RT and tolerate retreatment better?

Answer 2

Early-responding tissues (rapidly proliferating stem cells)

Potential toxicity to late-responding tissues is often limiting factor

If there is functional loss from prior RT exceeding tolerance, cannot re-irradiate

Question 3

What requirements are suggested for spinal cord re-RT?

Answer 3

> 1 year interval
Initial RT <90% of acceptable BED
Cumulative BED <130-135% of acceptable BED

Question 4

What BED causes brain necrosis (in the setting of re-RT)?

Answer 4

> 100 Gy

Question 5

How does kidney tolerance to re-RT differ from other tissues?

Answer 5

Tolerance DECREASES over time (suggests continuous progression of renal injury)