Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
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Randomized Controlled Trial Comparative Study
Randomized clinical trial on 7-days-a-week postoperative radiotherapy for high-risk squamous cell head and neck cancer.
To evaluate the normal tissue reactions and loco-regional control rates (LRC) in patients treated with 7-days-a-week postoperative continuous irradiation (p-CAIR) compared to conventionally fractionated 5-days-a-week postoperative radiotherapy (CF). ⋯ An improvement in LRC attributable to acceleration of postoperative radiotherapy appeared restricted to the patients with cancer of the oropharynx/oral cavity. In patients with cancer of the larynx acceleration of postoperative radiotherapy did not have any beneficial effect.
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The effectiveness of ABC has been traditionally measured as the reduction in internal margin (IM) within the planning target volume (PTV). Not to overestimate the benefit of ABC, the effect of patient movement during treatment also needs to be taken into account. We determined the IM and set-up error with ABC and the effect on physical lung parameters compared to standard margins used with free breathing. We also assessed interfraction oesophageal movement to determine a planning organ at risk volume (PRV). ⋯ The reduction in PTV size with ABC resulted in an 18-25% relative reduction in physical lung parameters. PTV margin reduction has the potential to spare normal lung and allow dose-escalation if coupled with image-guided RT. The oesophageal PRV needs to be considered when irradiating central disease and is of increasing importance with altered RT fractionation and concomitant chemoradiation schedules. Further reductions in PTV and PRV may be possible if patient set-up error was minimised, confirming that attention to patient immobilisation is as important as attempts to control tumour motion.
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Comparative Study
Biological effect of intermittent radiation exposure in vivo: recovery from sublethal damage versus reoxygenation.
In vivo effects of intermittent irradiation are influenced by recovery from sublethal damage (SLDR) and reoxygenation, so contribution of the two factors were investigated using murine tumors. ⋯ Reoxygenation occurring within 5-15 min appeared to compensate for SLDR in SCCVII tumors. When reoxygenation was limited, the decrease of radiation effect occurred due to SLDR.
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Evaluate the rationale for the proposals that prior to a wider use of proton radiation therapy there must be supporting data from phase III clinical trials. That is, would less dose to normal tissues be an advantage to the patient? ⋯ Proton therapy provides superior distributions of low LET radiation dose relative to that by photon therapy for treatment of a large proportion of tumor/normal tissue situations. Our assessment is that there is no medical rationale for clinical trials of protons as they deliver lower biologically effective doses to non-target tissue than do photons for a specified dose and dose distribution to the target. Based on present knowledge, there will be some gain for patients treated by proton beam techniques. This is so even though quantitation of the clinical gain is less secure than the quantitation of reduction in physical dose. Were proton therapy less expensive than X-ray therapy, there would be no interest in conducting phase III trails. The talent, effort and funds required to conduct phase III clinical trials of protons vs photons would surely be more productive in the advancement of radiation oncology if employed to investigate real problems, e.g. the most effective total dose, dose fractionation, definition of CTV and GTV, means for reduction of PTV and the gains and risks of combined modality therapy.
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The purpose of this study was to determine the 4D accumulated dose delivered to the CTV in stereotactic radiotherapy of lung tumours, for treatments planned on an average CT using an ITV derived from the Maximum Intensity Projection (MIP) CT. ⋯ When the target dose is prescribed to the ITV (PTV=ITV) and dose calculations are performed on the average CT, the cumulative CTV dose compares well to the planned dose to the ITV. Thus, the concept of treatment plan optimisation and evaluation based on the average CT and the ITV is a valid approach in stereotactic lung treatment. Even with a zero ITV to PTV margin, no significantly different dose coverage of the CTV arises from the breathing motion induced dose variation over time.