Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
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Comparative Study
Comparative analysis of intensity modulation inverse planning modules of three commercial treatment planning systems applied to head and neck tumour model.
Three commercial treatment planning modules for intensity modulated radiation therapy (IMRT) Inverse Planning, MDS-Nordion Helax-TMS, Varian Cadplan-Helios, and CMS Focus, were compared in an attempt to determine potential application limits or dosimetric differences among various optimisation algorithms. ⋯ Results obtained for the three IMRT TPS show in first instance that the optimisation algorithms analysed, as well as the conversion from computed fluences to multileaf sequences implemented in the planning systems can produce substantially equivalent dose plans (for target coverage and organs at risk sparing) if planning is performed with common strategies and once a strong understanding of each system feature is achieved. Secondly, a limited number of dose levels (about eight) is adequate at planning level.
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The relationship between the radiation dose and the risk of the osteoradionecrosis is well known. However, the dose to the mandible is not routinely assessed in the radiotherapy for head and neck cancer. The aim of our study was to analyze the mandibular dose distribution in the patients administered curative radiotherapy for squamous cell carcinoma of the oropharynx. Moreover, the clinical results have been analyzed. ⋯ Radiotherapy for oropharyngeal cancer is associated with high doses to the retromolar mandibular regions (the dose can be higher than prescribed in the ICRU reference point), ascending ramus and molar regions. Lower doses are absorbed at the condyles and mental symphysis. The single dose point (for example, the ICRU reference point) could be not used as a representative for the mandibular dose. In our small series of patients treated with hyperfractionated irradiation, these dose heterogeneities were not correlated to the patient- and treatment-related factors and are not related to the increased risk of late bone complications. The clinical relevance of mandibular dose distribution remains to be established in larger series of patients treated with conventionally and unconventionally fractionated irradiation.
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The purpose of this paper is to evaluate acute radiation-induced toxicity of carbon ion therapy. ⋯ Scanning beam delivery of heavy charged particles is safe and reliable. No unexpected acute dose limiting toxicity was observed. With regard to toxicity, a substantial improvement compared to passive beam shaping technology is achieved.
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Comparative Study
The dose to the parotid glands with IMRT for oropharyngeal tumors: the effect of reduction of positioning margins.
The aim of this paper is to quantify the importance of the reduction of positioning margins applied to the clinical target volume (CTV) on the dose distribution of the parotid gland for different intensity-modulated radiotherapy (IMRT) strategies for the treatment of oropharyngeal cancer. ⋯ Reducing the CTV-PTV margin by improving the patient position accuracy may lead to a significant reduction of NTCP for the IMRT treatment of the oropharyngeal tumors and lymph nodes level II.
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Multicenter Study
Relationships between DVHs and late rectal bleeding after radiotherapy for prostate cancer: analysis of a large group of patients pooled from three institutions.
Accurate modeling of late rectal reactions needs the collection of individual 3D dose-volume data (i.e. DVH) as well as clinical information of large cohorts of patients. The possibility of collecting a large number of patients with many different dose-volume combinations is very suitable for this purpose. ⋯ Our data confirm the role of the rectal DVH in separating groups of patients having prostate radiotherapy in low and high risk of developing late bleeding. Based on these results, V50 below 60-65% and V60 below 50-55% seem to be the robust cut-off values to keep the risk of developing late rectal bleeding reasonably low. However, due to the 'heterogeneity' of the considered population, the results found should be applied with caution in 'more homogeneous' groups of patients. The association of adjuvant hormone deprivation seems to be associated with an increased risk of rectal toxicity; the mechanism for this effect should be a focus of further research.