Normal Tissue Complication Probability after hypofractionation increased due to the high dose per fraction or the high total Biological Equivalent Dose?

摘要

Two recently published studies analysed the toxicity after hyp-ofractionated radiotherapy (RT) [1,2]. An important question is: could this toxicity be predicted from the delivered dose and historical toxicity models or was it unexpectedly high?The total biological dose for an Organ-At-Risk (OAR) after conventional fractionated radiotherapy (RT) is calculated as the Biological Equivalent Dose (BED) or Normalized Total Dose in 2 Gy per fraction {NTD_(2Gy)) according to the Linear Quadratic (LQ) model [3]. For hypofractionated regimens however, it is questionable whether the LQ-model is still valid [4,5]. Nowadays, more clinical data with longer follow-up are becoming available. It is important that the dose response analyses are accurately performed in order to answer the question whether the LQ model is valid and whether established dose-response relationships for OARs after conventional RT can be used after hypofractionated RT.