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Background:Validation of magnetic resonance imaging (MRI) and development of guidelines for the delineation of the gross tumor volume (GTV) is of utmost importance to benefit from the visibility of anatomical details on MR images and to achieve an accurate GTV delineation. In the ideal situation, the GTV delineation corresponds to the histopathologically determined ‘true tumor volume’. Consequently, we developed guidelines for GTV delineation of laryngeal and hypopharyngeal tumors on MRI and determined the accuracy of the resulting delineation of the tumor outline on histopathology as gold standard. Material and methods:Twenty-seven patients with T3 or T4 laryngeal/hypopharyngeal cancer underwent a MRI scan before laryngectomy. Hematoxylin and eosin sections were obtained from surgical specimens and tumor was delineated by one pathologist. GTV was delineated on MR images by three independent observers in two sessions. The first session (del1) was performed according to clinical practice. In the second session (del2) guidelines were used. The reconstructed specimen was registered to the MR images for comparison of the delineated GTVs to the tumor on histopathology. Volumes and overlap parameters were analyzed. A target margin needed to assure tumor coverage was determined. Results:The median GTVs (del1: 19.4 cm3, del2: 15.8 cm3) were larger than the tumor volume on pathology (10.5 cm3). Comparable target margins were needed for both delineation sessions to assure tumor coverage. By adding these margins to the GTVs, the target volumes for del1 (median: 81.3 cm3) were significantly larger than for del2 (median: 64.2 cm3) (p ≤ 0.0001) with similar tumor coverage. Conclusions:In clinical radiotherapy practice, the delineated GTV on MRI is twice as large as the tumor volume. Validated delineation guidelines lead to a significant decrease in the overestimation of the tumor volume. [ABSTRACT FROM PUBLISHER]

The article discusses a study aimed at determining the variation of tumor delineation among pathologists on H&E-sections for laryngeal and hyphpharyngeal carcinoma to quantify the uncertainties in the gold standard in the context of imaging validation studies for laryngeal and hypopharyngeal carcinoma. It suggests that delineation inaccuracies on images are larger than on histopathology.

Background and purpose.To determine the spatial correspondence between the gross tumor volume (GTV) delineated on computer tomography (CT) and the actual tumor on histopathology. Material and methods.Sixteen patients with T3 or T4 laryngeal or hypopharyngeal cancer underwent a CT scan before total laryngectomy. The GTV was delineated on CT by three independent observers and by consensus between the three observers. After surgery, whole-mount hematoxylin-eosin stained (H&E) sections were obtained. One pathologist delineated the tumor in the H&E sections (tumorH&E). The reconstructed specimen was registered to the CT scan in order to compare the GTV to the tumorH&Ein three dimensions. The overlap between the GTV and the tumorH&Ewas calculated and the distance between the volumes was determined. Results.Tumor tissue was delineated in 203 of 516 H&E sections. For 14 patients a detailed analysis could be performed. The GTV volume was on average 1.7 times larger than the volume of the tumorH&E. The mean coverage of the tumorH&Eby the consensus GTV was 88%. tumorH&Etissue was found at 1.6 mm to 12.9 mm distance outside the GTV depending on observer and patient. Conclusions.GTVs delineated on CT for laryngeal and hypopharyngeal cancer were 1.7 times larger than the tumor. Complete coverage of the tumor by the GTV was, however, not obtained. [ABSTRACT FROM AUTHOR]