The potential role of modern radiotherapy techniques in the treatment of malignant spinal cord compression: a dose planning study

AbstractAimTo investigate the doses given to the kidneys and the small intestines for three radiation therapy techniques [anterior–posterior (APPA) fields, three fields and volumetric-modulated arc therapy (VMAT)] for spinal cord compression (SCC) patients with metastatic disease in the lower thoracic or lumbar spine and to monitor the time spent by clinicians and dose planners.IntroductionRadiation therapy is one of the main treatment modalities for SCC. Typical palliative radiation therapy techniques have used APPA fields or a three-field technique.However, as delivery techniques have evolved dramatically over the past decades, VMAT has gained wide acceptance. VMAT allows for a dose reduction in the organs at risk. Such a dose reduction may result in less toxicity.The use of the VMAT technique may require more time for contouring and planning compared with the APPA and three-field techniques. Any potential dosimetric benefit of VMAT must not be outweighed by large amounts of extra time spent by clinicians and dose planners.Materials and methodsFor 20 patients treated with radiation therapy for SCC at our hospital, we created a VMAT plan, and the more traditionally used APPA and three-field plans. The mean kidney doses and the volume of bowel, which received 20 Gy, were extracted for each plan. The correlations between parameters for three techniques were determined.Furthermore, the time required for contouring targets for five patients; and the time required to plan five patients, was recorded.ResultsVMAT lead to the most conformal distributions: the high-dose areas were restricted to the target volume, whereas the healthy tissue, especially the bowel, received a lower dose. In contrast, the APPA plan lead to a larger volume of bowel being irradiated, whereas the three-field technique spared the bowel at the expense of a higher dose to the kidneys.The average contouring time was 16 minutes, the average planning time was 38 minutes.ConclusionPatients treated for SCC in the lower thoracic or lumbar region may benefit from VMAT treatment, as it reduces the dose to the bowel and kidneys compared with APPA or three-field treatments.</jats:sec

Interobserver delineation uncertainty in involved-node radiation therapy (INRT) for early-stage Hodgkin lymphoma: on behalf of the Radiotherapy Committee of the EORTC lymphoma group

Contains fulltext : 173026.pdf (publisher's version ) (Open Access)BACKGROUND AND PURPOSE: In early-stage classical Hodgkin lymphoma (HL) the target volume nowadays consists of the volume of the originally involved nodes. Delineation of this volume on a post-chemotherapy CT-scan is challenging. We report on the interobserver variability in target volume definition and its impact on resulting treatment plans. MATERIALS AND METHODS: Two representative cases were selected (1: male, stage IB, localization: left axilla; 2: female, stage IIB, localizations: mediastinum and bilateral neck). Eight experienced observers individually defined the clinical target volume (CTV) using involved-node radiotherapy (INRT) as defined by the EORTC-GELA guidelines for the H10 trial. A consensus contour was generated and the standard deviation computed. We investigated the overlap between observer and consensus contour [Sorensen-Dice coefficient (DSC)] and the magnitude of gross deviations between the surfaces of the observer and consensus contour (Hausdorff distance). 3D-conformal (3D-CRT) and intensity-modulated radiotherapy (IMRT) plans were calculated for each contour in order to investigate the impact of interobserver variability on each treatment modality. Similar target coverage was enforced for all plans. RESULTS: The median CTV was 120 cm3 (IQR: 95-173 cm3) for Case 1, and 255 cm3 (IQR: 183-293 cm3) for Case 2. DSC values were generally high (>0.7), and Hausdorff distances were about 30 mm. The SDs between all observer contours, providing an estimate of the systematic error associated with delineation uncertainty, ranged from 1.9 to 3.8 mm (median: 3.2 mm). Variations in mean dose resulting from different observer contours were small and were not higher in IMRT plans than in 3D-CRT plans. CONCLUSIONS: We observed considerable differences in target volume delineation, but the systematic delineation uncertainty of around 3 mm is comparable to that reported in other tumour sites. This report is a first step towards calculating an evidence-based planning target volume margin for INRT in HL