WE-B-304-03: Biological Treatment Planning



The ultimate goal of radiotherapy treatment planning is to find a treatment that will yield a high tumor control probability (TCP) with an acceptable normal tissue complication probability (NTCP). Yet most treatment planning today is not based upon optimization of TCPs and NTCPs, but rather upon meeting physical dose and volume constraints defined by the planner. It has been suggested that treatment planning evaluation and optimization would be more effective if they were biologically and not dose/volume based, and this is the claim debated in this month's Point/Counterpoint. After a brief overview of biologically and DVH based treatment planning by the Moderator Colin Orton, Joseph Deasy (for biological planning) and Charles Mayo (against biological planning) will begin the debate.

Some of the arguments in support of biological planning include:

  • this will result in more effective dose distributions for many patients
  • DVH-based measures of plan quality are known to have little predictive value
  • there is little evidence that either D95 or D98 of the PTV is a good predictor of tumor control
  • sufficient validated outcome prediction models are now becoming available and should be used to drive planning and optimization
  • Some of the arguments against biological planning include:
  • several decades of experience with DVH-based planning should not be discarded
  • we do not know enough about the reliability and errors associated with biological models
  • the radiotherapy community in general has little direct experience with side by side comparisons of DVH vs biological metrics and outcomes
  • it is unlikely that a clinician would accept extremely cold regions in a CTV or hot regions in a PTV, despite having acceptable TCP values

Learning Objectives:

  • 1.To understand dose/volume based treatment planning and its potential limitations
  • 2.To understand biological metrics such as EUD, TCP, and NTCP
  • 3.To understand biologically based treatment planning and its potential limitations