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Considerations of the growing child and difficulties in interpretation of the radiotherapy information in the treatment protocols were identified as reasons for the variation. As a result, clarified translated detailed radiotherapy guidelines for paediatric/adolescent patients have been recognised as a way to reduce this variation.

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a b s t r a c tBackground and purpose: Substantial inter-observer variations in target delineation have been presented previously. Target delineation for paediatric cases is difficult due to the small number of children, the variation in paediatric targets, the number of study protocols, and the individual patient's specific needs and demands. Uncertainties in target delineation might lead to under-dosage or over-dosage. The aim of this work is to apply the concept of a consensus volume and good quality treatment plans to visualise and quantify inter-observer target delineation variations in dosimetric terms in addition to conventional geometrically based volume concordance indices. Material and methods: Two paediatric cases were used to demonstrate the potential of adding dose metrics when evaluating target delineation diversity; Hodgkin's disease (case 1) and rhabdomyosarcoma of the parotid gland (case 2). The variability in target delineation (PTV delineations) between six centres was quantified using the generalised conformity index, CIgen, generated for volume overlap. The STAPLE algorithm, as implemented in CERR, was used for both cases to derive a consensus volumes. STAPLE is a probabilistic estimate of the true volume generated from all observers. Dose distributions created by each centre for the original target volumes were then applied to this consensus volume. Results: A considerable variation in target segmentation was seen in both cases. For case 1 the variation was 374-960 cm 3 (average 669 cm 3 ) and for case 2; 65-126 cm 3 (average 109 cm 3 ). CIgen were 0.53 and 0.70, respectively. The DVHs in absolute volume displayed for the delineated target volume as well as for the consensus volume adds information on both ''compliant" target volumes as well as outliers which are hidden with just the use of concordance indices. Conclusions: The DVHs in absolute volume add valuable and easily understood information to various indices for evaluating uniformity in target delineation.

Purpose: To evaluate the roles of preradiotherapy hemoglobin level and microvessel density (MVD) as predictive factors for tumor control and survival in patients with laryngeal cancer treated with primary radiotherapy.Experimental Design: Two hundred and fourteen patients with stage I-IV laryngeal cancer were included in the analysis. Patients were treated with once daily fractionated radiotherapy over 6.5 weeks or twice daily fractionated radiotherapy over 4.5 weeks up to total doses of 62 to 68 Gy. Preradiotherapy hemoglobin levels were obtained from patient journals, and pretreatment tumor biopsies were stained with CD34 antibody for the counting of microvessels. The prognostic implication of preradiotherapy hemoglobin level and MVD on tumor control and survival was tested.Results: Five-year locoregional control probability was 88.9% for patients with preradiotherapy hemoglobin levels >137.5 g/L (median) and 64.4% for patients with preradiotherapy hemoglobin levels <137.5 g/L (P ‫؍‬ 0.01). The corresponding figures for disease-free survival were 87.8 and 62.8% (P ‫؍‬ 0.007), respectively, and for overall survival 58.1 and 40.3% (P < 0.001), respectively.In multivariate analysis, tumor stage and preradiotherapy hemoglobin level were significant prognostic factors for locoregional control and disease-free survival, whereas tumor stage, preradiotherapy hemoglobin-level, gender, and age were significant prognostic factors for overall survival. No correlation was found between MVD and tumor control and survival.Conclusion: Preradiotherapy hemoglobin level, but not MVD, predicts locoregional control and survival in patients with laryngeal cancer treated with radiotherapy.