When To Reirradiate

Reirradiation refers to radiation of an area which has been radiated to full radical doses previously. The following section is a discussion of dilemmas facing the oncologist choosing to re irradiate a patient. This is a very interesting topic which is not dealt with adequately in standard oncology textbooks. The issue with reirradation is two fold:

  1. Increasing late normal tissue toxicity that can kill or severly impair the QOL
  2. Diminishing gains in the treatment of a possibly radioresistent tumor

Part I: Basic Radiobiology of Reirradiation

A short 10 slide discussion of the radiobiology involved in reirradiation. Discussed inside is how does DNA damage occur, the concept of cluster damage and how important is DNA damage to the genesis of late normal tissue reactions. This basic knowledge will allow the concept of repair and recovery of dose that will appear in subsequent presentations.

Part II: Animal Experiments in Reirradiation

A short discussion of the available preclinical data with regards to tolerance and "recovery" after reirradiation is presented. The preclinical knowledge is important as it defines the safe threshold for human reirradiation and is the basis behind human reirradiation by most experienced groups. However the most important disadvante with respect to these preclinical data are:

  1. Diverse radiobiological responses amongst animal and different tolerance thresholds
  2. Relatively shorter follow up due to the life span of the animal
  3. Moral, financial and ethical issues with long term and large scale animal experiments

For those interested selected bibliography is provided below:
1. Ang KK, Jiang G-L, Feng Y, Stephens LC, Tucker SL, Price RE. Extent and kinetics of recovery of occult spinal cord injury. International Journal of Radiation Oncology*Biology*Physics. 2001 Jul 15;50(4):1013-1020.
2. Bourgier C, Vozenin M-C, Deutsch É. Réirradiation des tissus sains : données radiobiologiques précliniques. Cancer/Radiothérapie. 2010 Oct;14(6-7):412-415.
3. HAVEMAN J, RODERMOND H, BREE C van, WONDERGEM J, FRANKEN NAP. Residual late radiation damage in mouse stromal tissue assessed by the tumor bed effect. Journal of Radiation Research. 2007;48(2):107-112.
4. Simmonds RH, Hopewell JW, Robbins ME. Residual radiation-induced injury in dermal tissue: implications for retreatment. Br J Radiol. 1989 Oct;62(742):915-920.

Part III: Human data with Reirradiation

Coming soon…

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