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Aims: To evaluate the usefulness of a contouring course in reducing inter- and intraobserver variability in the definition of the larynx as organ at risk (OAR)., Methods: Within the "Rete Oncologica Piemonte-Valle d'Aosta" network, a contouring course focusing on larynx delineation was proposed. Twenty-six radiotherapist technicians (RTTs) experienced in delineating OARs were asked to contour larynx before and after the training. An expert radiation oncologist defined the reference volume for educational purpose. The contoured volumes obtained before and after the course were compared using descriptive statistics (mean value, standard deviation-SD, and coefficient of variation-COV) of volumes and maximum diameters. Conformity index (CI), dice coefficient (DC), and percentage of overlap were used to evaluate the spatial accuracy of the different volumes compared to the reference. Further analysis regarding the variation in the centre of mass (COM) displacement was performed., Results: The mean volume was 40.4 cm 3 before and 65.9 cm 3 after the course, approaching the reference value. Mean anteroposterior, laterolateral, and craniocaudal diameters improved, getting each closer to the reference. Moreover, the COM moved approaching reference coordinates. Mean percentage of intersection and DC strongly increased after the course, rising from 57.76 to 93.83 % and from 0.68 to 0.89, respectively. CI enhanced from 0.06 to 0.31., Conclusions: This study shows an improvement in larynx definition after the contouring course with lower interobserver variability and major consistency compared to the reference volume. Other specific educational activities may further increase the quality of radiation therapy contouring in this setting.

Conservative surgery followed by radiotherapy is the current treatment of choice for primary breast cancer: indeed, this protocol ensures local control, relatively good cosmetic results and NED survival values similar to those of more invasive surgery. Radiotherapy requires the optimization of the irradiation technique to minimize the dose to the organs at risk. To this purpose, 30 patients submitted to quadrantectomy for breast carcinoma and then to radiotherapy on the residual breast were examined, January through December, 1994, at the Radiotherapy Service of the Ivrea Hospital, to investigate if CT can help optimize treatment planning, sparing as much of the pulmonary tissue underlying the residual breast as possible. Our series of patients was then compared with a literature series whose treatment had been planned only on the mapping of body outline. Some interesting considerations follow from our results: 1) With CT, larger fields can be used than those used with the body outline, so that the planned target volume can be more closely approached; 2) Larger fields can be used because the critical organ included in the irradiation field is more correctly and precisely defined; 3) The comparison with the literature shows that in the past the fields were larger, because the target volume and the critical organ were more difficult to define. The use of larger fields means a higher dose to the lung and thus maybe a higher risk of radiation pneumonia.