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M. Oudkerk



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    MA01 - Improvement and Implementation of Lung Cancer Screening (ID 368)

    • Event: WCLC 2016
    • Type: Mini Oral Session
    • Track: Radiology/Staging/Screening
    • Presentations: 1
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      MA01.07 - Influence of Nodule Morphology on Inter-Reader Variability of Volume and Diameter Measurements in CT Lung Cancer Screening (ID 4750)

      11:36 - 11:42  |  Author(s): M. Oudkerk

      • Abstract
      • Presentation
      • Slides

      Background:
      The high number of false positive screen results is a major disadvantage of lung cancer screening by low-dose chest computed tomography (CT). Measurement strategy influences the false-positive rate, and nodule morphology may influence measurement of nodule size. Comparison between inter-reader variation for semi-automatic volume measurements and manual diameter measurements are scarce. Therefore, we aimed to evaluate the influence of nodule morphology on inter-reader variability and assessment of growth for semi-automatic volume measurements and manual diameter measurements, in intermediate-sized solid nodules found in CT lung cancer screening.

      Methods:
      Twenty-five nodules of each morphological category: smooth, lobulated, spiculated and irregular, were randomly selected from 93 participants of the Dutch-Belgian randomized lung cancer screening trial (NELSON). Semi-automatic volume measurements were performed using Syngo LungCARE[®] software. Two chest radiologists independently measured maximum and mean diameters manually. The impact of nodule morphology on inter-reader variability was evaluated based on the systematic error and 95% limits of agreement (LoA). Inter-reader variability was compared to volume change cutoff at 3-month follow-up based on NELSON for nodule growth and Lung-RADS diameter cutoff.

      Results:
      For manual diameter measurements, a significant systematic deviation was found between readers in smooth, lobulated, and spiculated nodules. The deviation was up to 1.5 mm based on maximum diameter measurements, and 1.2 mm based on mean diameter measurements. For semi-automatic volume measurements, no statistically significant systematic deviation was found. For lobulated, spiculated, and irregular nodules, the 95%-LoA for mean diameter measurements was up to 66% larger than the 1.5 mm cutoff for nodule growth. For volume measurements, the 95%-LoA exceeded the 25% growth cutoff for spiculated and irregular nodules, but only by up to 12%.

      Conclusion:
      Nodule morphology has a greater effect on size assessment based on manual diameter measurements than based on volume measurements. The larger inter-reader variability for manual diameter measurement may cause misclassification of spiculated nodules when assessing growth in 24% of cases. Therefore, semi-automatic volume measurement is recommended for nodule size and growth determination in CT lung cancer screening.

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    P1.03 - Poster Session with Presenters Present (ID 455)

    • Event: WCLC 2016
    • Type: Poster Presenters Present
    • Track: Radiology/Staging/Screening
    • Presentations: 1
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      P1.03-042 - Nodule Size is Poorly Represented by Nodule Diameter in Low-Dose CT Lung Cancer Screening (ID 6009)

      14:30 - 14:30  |  Author(s): M. Oudkerk

      • Abstract

      Background:
      In lung cancer screening, at least one pulmonary nodule is found in over 50% of participants, of which 99% is benign. As lung cancer probability in low-dose computed tomography (CT) lung cancer screening usually is based on nodule size and growth rate, accurate nodule size determination is of major importance to decrease false positive screen results. Previous studies showed that nodule size measurements based on semi-automated volume are preferred over diameter measurements. Aim of this study was to determine the correlation between nodule diameter and nodule size of nodules found in low-dose CT lung cancer screening, and to directly compare it with semi-automated volume measurements.

      Methods:
      We investigated baseline data of 2,240 solid nodules of intermediate size (volume 50-500mm[3]) in 1,500 lung cancer screening participants. Nodule volume, x, y, and z diameter and minimum / maximum diameter in any direction were generated by semi-automated software (LungCARE, Siemens). Range in maximum axial and mean nodule diameter per nodule volume category (50-100mm[3], 100-200mm[3], 200-300mm[3], 300-400mm[3], 400-500mm[3]) was determined. Semi-automated nodule volume represented nodule size. Intra-nodule diameter variation was defined as maximum minus minimum nodule diameter.

      Results:
      Median participant age was 59 years, 14.1% were women. Median nodule volume was 82.4 mm[3] (interquartile range [IQR], 62.9–125.4 mm[3]). Median nodule diameter was 6.1 mm (IQR, 5.4–7.2 mm) for mean diameter, and 6.6 mm (IQR, 5.9–7.7 mm) for maximum axial diameter. Range in mean nodule diameter per volume category varied from 8.55 mm (3.0 – 11.5 mm) for nodules with volume of 50-100 mm[3] to 6.1 mm (7.2 – 13.3 mm) for nodules with volume of 200-300 mm[3]; range in maximum axial diameter varied from 11.2 mm (7.3 – 18.5 mm) for nodules with volume of 200-300 mm[3], to 7.0 mm (9.1 – 16.1 mm) for nodules with volume of 400-500 mm[3]. Intra-nodule diameters varied by a median of 2.8 mm (IQR, 2.2-3.7 mm). Intra-nodule diameter variation for smaller intermediate-sized nodules (50-200 mm[3]) was 2.8 mm (IQR 2.2-3.5 mm), and was smaller than intra-nodule diameter variation for larger intermediate-sized nodules (200-500 mm[3]; median 3.6 mm [IQR 2.5-5.1 mm], P<0.01).

      Conclusion:
      Nodule size is poorly represented by diameter, as a nodule has an infinite number of diameters, but only one volume. Therefore, use of nodule diameter measurements may lead to misclassification of lung cancer probability. Median intra-nodule diameter variation was found to be higher as the 1.5mm LungRADS cutoff for nodule growth.