Adaptive radiotherapy for head and neck tumors

Introduction Intensity modulated radiotherapy (IMRT) improves the quality of life for patient treated for head and neck tumors. This improvement can be optimized if the treatment is adapted to the anatomical variations occurring during the treatment [1] , [2] . The aim of this study is to provide a fast and accurate method for replanification, in order to define new criteria of decision in treatment adaptation. Methods The study includes 3 patients treated by IMRT technique with a simultaneous integrated boost (SIB). For each patient, a planification computed tomography scan and a weekly CBCT (Cone Beam Computed Tomography) are performed. An elastic registration is performed with the RayStation treatment planning system (RaySearch, V 5.0.2) to propagate the structures and dose distribution from the initial CT scan to the CBCT. The quality of the propagation of the structures is evaluated with the DICE index, compared to the delineation of the radiotherapist. The distortion of the dose distribution is also evaluated. Finally, the totalized dose distribution is calculated in order to analyze the impact of the adaptation of the treatment. Results Firsts results shows a mean Dice index of 0,8 for the thyroid, 0,7 for the medullar canal, 0,7 for mandibles, 0,7 for CTVs and 0,7 for parotids. The mean dose difference between the planification and the delivered dose shows a decrease of 5% for the CTVs and an increase of 4% for the parotids. Other results are still processing. Conclusion This study proposes a method for evaluating the delivered dose for head and neck tumors treated by IMRT techniques. The delivered dose could be an effective tool when comes the decision of a replanification during the treatment.