Browsing Academic Department of Radiation Oncology - ADRO by Subjects
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Evaluation of larynx-sparing techniques with IMRT when treating the head and neck.PURPOSE: Concern exists that widespread implementation of whole-field intensity-modulated radiotherapy (IMRT) for the treatment of head-and-neck cancer has resulted in increased levels of dysphagia relative to those seen with conventional planning. Other investigators have suggested an alternative junctioned-IMRT (J-IMRT) method, which matches an IMRT plan to a centrally blocked neck field to restrict the laryngeal dose and reduce dysphagia. The effect on target coverage and sparing of organs at risk, including laryngeal sparing, in the optimization was evaluated and compared with that achieved using a J-IMRT technique. METHODS AND MATERIALS: A total of 13 oropharyngeal cancer whole-field IMRT plans were planned with and without including laryngeal sparing in the optimization. A comparison of the target coverage and sparing of organs at risk was made using the resulting dose-volume histograms and dose distribution. The nine plans with disease located superior to the level of the larynx were replanned using a series of J-IMRT techniques to compare the two laryngeal-sparing techniques. RESULTS: An average mean larynx dose of 29.1 Gy was achieved if disease did not extend to the level of the larynx, with 38.8 Gy for disease extending inferiorly and close to the larynx (reduced from 46.2 and 47.7 Gy, respectively, without laryngeal sparing). Additional laryngeal sparing could be achieved with J-IMRT (mean dose 24.4 Gy), although often at the expense of significantly reduced coverage of the target volume and with no improvement to other areas of the IMRT plan. CONCLUSION: The benefits of J-IMRT can be achieved with whole-field IMRT if laryngeal sparing is incorporated into the class solution. Inclusion of laryngeal sparing had no effect on other parameters in the plan.
Monitoring dosimetric impact of weight loss with kilovoltage (kV) cone beam CT (CBCT) during parotid-sparing IMRT and concurrent chemotherapy.Parotid-sparing head-and-neck intensity-modulated radiotherapy (IMRT) can reduce long-term xerostomia. However, patients frequently experience weight loss and tumor shrinkage during treatment. We evaluate the use of kilovoltage (kV) cone beam computed tomography (CBCT) for dose monitoring and examine if the dosimetric impact of such changes on the parotid and critical neural structures warrants replanning during treatment.
Use of multiple biological markers in radiotherapy-treated head and neck cancer.OBJECTIVE: Management of patients with head and neck squamous cell carcinoma is often based on clinical parameters, with little appreciation of the underlying tumour biology. Single biological marker studies fail to acknowledge the complexity of these tumours. Our aim was to define a profile of biological markers associated with outcome. DESIGN: This retrospective study involved consecutive patients with oropharyngeal squamous cell carcinoma treated with primary radiotherapy between 1996 and 2001. Pre-treatment biopsies were used to study the immunohistochemical expression of nine biological markers. Markers were chosen to reflect biologically relevant pathways. RESULTS: Following analysis of nine markers, a profile of two markers was derived (carbonic anhydrase 9 and major vault protein), the co-expression of which conferred a significantly poor probability of locoregional control. The prognostic effect of these biomarkers in combination was greater than their effect individually. CONCLUSION: Biomarker profiles can be established which highlight large differences in locoregional control. Identifying tumours that express both carbonic anhydrase 9 and major vault protein may facilitate patient selection for more aggressive treatment.