Endometrial cancer off-line staging using two-dimensional transvaginal ultrasound and three-dimensional volume contrast imaging: Intermethod agreement, interrater reliability and diagnostic accuracy

Objectives The aim is to estimate agreement between two-dimensional transvaginal ultrasound (2D-TVS) and three-dimensional volume contrast imaging (3D-VCI) in diagnosing deep myometrial invasion (MI) and cervical stromal involvement (CSI) of endometrial cancer and to compare the two methods regarding inter-rater reliability and diagnostic accuracy. Methods Fifteen ultrasound experts assessed off-line de-identified 3D-VCI volumes and 2D-TVU video clips from 58 patients with biopsy-confirmed endometrial cancer regarding the presence of deep (≥50%) MI and CSI. Video clips and 3D volumes were assessed independently. Interrater reliability was measured using kappa statistics. Histological diagnosis after hysterectomy served as gold standard. Accuracy measurements were correlated to rater experience using Spearman's rank correlation coefficient (ρ). Results Agreement between 2D-TVU and 3D-VCI for diagnosing MI was median 76% (range 64–93%) and for CSI median 88% (range 79–97%). Interrater reliability was better for 2D-TVU than for 3D-VCI (Fleiss' kappa 0.41 vs. 0.31 for MI and 0.55 vs. 0.45 for CSI). Median accuracy for diagnosing deep MI was 76% (range 59–84%) with 2D-TVU and 69% (range 52–83%) for 3D-VCI; the corresponding figures for CSI were 88% (range 81–93%) and 86% (range 72–95%). Accuracy was significantly correlated to how many cases the raters assessed annually. Conclusions Off-line assessment of MI and CSI in women with endometrial cancer using 3D-VCI has lower interrater reliability and lower accuracy than 2D-TVU video clip assessment. Since accuracy was correlated to the number of cases assessed annually it is advised to centralize these examinations to high-volume centres.