The clinical impact of observer variability in lung nodule
classification in children with Wilms Tumour
Abstract
Objectives To investigate the extent to which observer variability of CT
lung nodule assessment may affect clinical treatment stratification in
Wilms Tumor (WT) patients, according to the recent SIOP-RTSG UMBRELLA
protocol. Methods I: CT thoraces of children with WT submitted for
central review, were used to estimate size distribution of lung
metastases. II: Scans were selected for blinded review by five
radiologists to determine intra and inter-observer variability. They
assessed identical scans on two occasions six months apart. III: Monte
Carlo simulation (MCMC) was used to predict the clinical impact of
observer variation when applying the UMBRELLA protocol size criteria.
Results Lung nodules were found in 84 out of 360 (23%) children with
WT. For 21 identified lung nodules, inter-observer limits of agreement
(LOA) for the five readers were ±2.4mm and ±1.4mm (AP diameter), ±1.9mm
and ±1.8mm (TS diameter) and ±2.0mm and ±2.4mm (LS diameter) at
assessments 1 and 2. Intra-observer LOA across the three dimensions were
±1.5mm, ±2.2mm, ±3.5mm, ±3.1mm and ± 2.6mm (readers 1-5). MCMC
demonstrated that 17% of the patients with a ‘true’ nodule size of 3mm
will be scored as <3 mm, and 21% of the patients with a
‘true’ nodule size of <3mm will be scored as being 3 mm.
Conclusion A significant intra-inter observer-variation was found when
measuring lung nodules on CT for patients with WT. This may have
significant implications on treatment stratification, and thereby
outcome, when applying a threshold of 3 mm for a lung nodule to dictate
metastatic status.