title: 3D radiobiological evaluation of combined radiotherapy and hyperthermia treatments.
abstract: OBJECTIVE
  Currently, clinical decisions regarding thermoradiotherapy treatments are based on clinical experience. Quantification of the radiosensitising effect of hyperthermia allows comparison of different treatment strategies, and can support clinical decision-making regarding the optimal treatment. The software presented here enables biological evaluation of thermoradiotherapy plans through calculation of equivalent 3D dose distributions.
  
  
  METHODS
  Our in-house developed software (X-Term) uses an extended version of the linear-quadratic model to calculate equivalent radiation dose, i.e. the radiation dose yielding the same effect as the thermoradiotherapy treatment. Separate sets of model parameters can be assigned to each delineated structure, allowing tissue specific modelling of hyperthermic radiosensitisation. After calculation, the equivalent radiation dose can be evaluated according to conventional radiotherapy planning criteria. The procedure is illustrated using two realistic examples. First, for a previously irradiated patient, normal tissue dose for a radiotherapy and thermoradiotherapy plan (with equal predicted tumour control) is compared. Second, tumour control probability (TCP) is assessed for two (otherwise identical) thermoradiotherapy schedules with different time intervals between radiotherapy and hyperthermia.
  
  
  RESULTS
  The examples demonstrate that our software can be used for individualised treatment decisions (first example) and treatment optimisation (second example) in thermoradiotherapy. In the first example, clinically acceptable doses to the bowel were exceeded for the conventional plan, and a substantial reduction of this excess was predicted for the thermoradiotherapy plan. In the second example, the thermoradiotherapy schedule with long time interval was shown to result in a substantially lower TCP.
  
  
  CONCLUSIONS
  Using biological modelling, our software can facilitate the evaluation of thermoradiotherapy plans and support individualised treatment decisions.
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: C M
authors.initials: CM
authors.lastname: van Leeuwen
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Crezee
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.|b Laboratory for Experimental Oncology and Radiobiology (LEXOR)/Center for Experimental Molecular Medicine , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: A L
authors.initials: AL
authors.lastname: Oei
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.|b Laboratory for Experimental Oncology and Radiobiology (LEXOR)/Center for Experimental Molecular Medicine , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: N A P
authors.initials: NAP
authors.lastname: Franken
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: L J A
authors.initials: LJA
authors.lastname: Stalpers
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Bel
authors.affiliation: a Department of Radiation Oncology , Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: H P
authors.initials: HP
authors.lastname: Kok
keywords: Radiotherapy; biological modelling; hyperthermia; treatment planning