Carbon ion radiotherapy: Clinical aspects of dose reporting and treatment results at GSI

For carbon ion radiotherapy (RT), target volumes and organs at risk are defined according to the ICRU recommendations for conformal RT. Immobilization and precision of beam delivery are prerequisite. Treatment plan quality criteria used for the assessment of photon plans do also apply to carbon ion therapy plans. However, the reporting of physical doses alone is not sufficient, but biologically effective dose distributions and dose volume histogram (DVH) data have to be reported as well. Using active beam delivery techniques, the biological effective dose is not prescribed to a reference point but to each voxel. The α/β values used for biological treatment plan optimization need to be indicated as well. It is advisable to report the α/β values for the dose limiting toxicity and to optimize the plans according to this biological endpoint. The estimated α/β value for the specific tumour cell type and an additional treatment optimization for this endpoint might be reported as well in cases where α/β ratios for the dose-limiting toxicity and the specific tumour cell type are expected to differ substantially. The data reported should be compatible with the existing ICRU recommendations and should be sufficient to allow for clinical validation of the biological model used for biological plan optimization. Correction of minor systematic deviances of e.g. less than 5% should be enabled. Regular updates of the treatment planning software due to improvements/changes of the underlying beam model are needed in the future. To facilitate retrospective correlation of the collected clinical data with the model estimations and intercomparison of clinical data between different particle centres, the applied planning software version needs to be reported for each patient in the treatment protocol. (author)