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M. Oudkerk
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E01 - LDCT Screening (ID 1)
- Event: WCLC 2013
- Type: Educational Session
- Track: Imaging, Staging & Screening
- Presentations: 1
- Moderators:U. Pastorino, J.M.A. Daniels
- Coordinates: 10/28/2013, 14:00 - 15:30, Parkside Auditorium, Level 1
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E01.2 - Volumetrics for Nodule Assessment (ID 373)
14:25 - 14:45 | Author(s): M. Oudkerk
- Abstract
- Presentation
Abstract
Introduction Lung cancer is a major health problem with no improvement in survival over the last decades. At time of diagnosis, lung cancer is often already in advanced stage, with 5-year survival of no more than 15%. Currently, several lung cancer screening trials investigating whether early detection of lung cancer in high-risk individuals will reduce lung cancer mortality are ongoing. In 2011, the National Lung Screening Trial (NLST), was the first and to date only reporting a 20% decrease in lung cancer mortality when three rounds of annual low-dose computed tomography (CT) were compared with three annual rounds of chest X-ray screening. A major challenge, however, is the high rate of positive test results reported by the NLST (24.2%). No less than 96.2% of these comprised false-positive test results, causing unnecessary patient anxiety, radiation exposure and cost. The Dutch-Belgian lung cancer screening trial (Dutch acronym: NELSON study) was launched in September 2003. The NELSON study is an ongoing multicentre randomized controlled multi-detector low-dose CT lung cancer screening trial. The primary object is to investigate whether chest CT screening in year 1, 2, 4 and 6.5 will decrease lung cancer mortality by at least 25% in high-risk (ex-)smokers between 50 and 75 years of age compared to a control group receiving no screening. The NELSON study is the first lung cancer screening trial in which nodule management is based on nodule volume, instead of transverse cross-sectional nodule diameter for new nodules, and nodule growth in terms of volume doubling time (VDT) for existing ones. In this presentation, different aspects of nodule management in the NELSON study will be discussed. Volume detection thresholds Sensitive pulmonary nodule detection is crucial not to miss any lung cancer in a screening setting. The sensitivity of nodule detection was investigated by scanning a Lungman phantom according to the standard NELSON protocol. Nodules of five different volumes (range 14–905mm[3]) were randomly positioned in the phantom. A sensitivity of 100% was found for nodules with a volume equal to or larger than 65mm[3] (5mm), and a sensitivity of 60–80% was found for solid nodules with a volume of 14mm[3] (3mm). Since the lung cancer probability of lung nodules smaller than 50mm[3] or 4mm is neglectable, the sensitivity of nodule detection using the NELSON protocol is sufficient for accurate detection of malignant lung nodules. Measurement reproducibility For accurate decision making in serial CT studies, nodule measurement reproducibility is essential. A sub-study of the NELSON trial showed a difference in repeatability among three reconstruction settings, demonstrating that the use of consistent reconstruction parameters is important. Volume measurements of pulmonary nodules obtained at 1mm section thickness combined with a soft kernel were found to be most repeatable. Another sub-study showed that variability on volume measurements is related to nodule size, morphology and location. Besides image reproducibility, interobserver variability in performing semi-automated volume measurements is of major importance in the classification of lung nodules. Gietema et al. found that interobserver correlation was very high (r=0.99) in small-to-intermediate size (15-500mm[3]) nodules. Volume criteria for nodule stratification For solid nodules, and solid components of part-solid nodules, volume was calculated by 3-dimensional volumetric computer assessment, using LungCare software (version Somaris/5:VA70C-W; Siemens Medical Solutions). The final screen result was based on the nodule with largest volume or fasted growth. In the NELSON study, nodules were classified as negative if volume was <50mm[3] (4.6mm diameter if the nodule would have been perfectly spherical), leading to an invitation for the regular next-round CT, as positive if nodule volume was >500mm[3] (>9.8mm diameter), leading to direct referral to a pulmonologist for further workup, and as indeterminate in case of volume of 50-500mm[3]. Indeterminate nodules underwent a 6-week to 3-month follow-up low-dose CT for growth assessment. Volumetric growth assessment of pulmonary nodules After a nodule has been selected by a radiologist, the LungCare software automatically calculates nodule volume. Information is saved in the NELSON Management System (NMS), which calculates the growth in case of a pre-existing nodule. Growth is defined as a change in volume of ≥25% between two subsequent scans according to the formula: Percentage volume change (%) = (V2-V1)/V1)*100 V2 = volume at last CT, and V1 = volume at previous examination. Determination of the volume-doubling time For solid nodules, or solid components of partial-solid nodules with PVC≥25%, the VDT is semi-automatically calculated by the NMS according to the formula: VDT (days) = (ln(2)*Δt)/(ln(V2/V1)) The VDT is used to distinguish between positive screens (VDT<400days), requiring additional diagnostic procedures, indeterminate screens (VDT 400-600days), requiring an extra follow-up CT 12 months after the regular round CT and negative screens (VDT>600days). Using this two-step approach of volume and growth assessment, 2.6% of NELSON baseline screens were positive, and compared to other screening trials, a higher proportion (34.6% at baseline) were true-positive. The NELSON study reported a baseline screen sensitivity of 94.6% and a negative predictive value of 99.9%. Comparison between volumetric and diameter assessment of pulmonary nodules For determining pulmonary nodule size, the use of volume measurements has been found to be more reliable than diameter measurements. In the previously mentioned phantom study, measurements of the manually measured maximal transverse diameter and semi-automated measurements of diameter and nodule volume were compared with actual properties. In both methods, diameter and volume of the spherical nodules were significantly underestimated. In diameter evaluation, the overall underestimation for solid nodules was about 10% using the manual method, compared with less than 4% using the semi-automated method. In volumetry, the overall underestimation for solid nodules was about 25% (translates into 8% diameter underestimation) using the manual method, compared with less than 8% (translates into 2.5% diameter underestimation) using the semi-automated method. It is important to keep in mind that a small change in diameter already corresponds to a considerably higher change in volume. Thus, in lung cancer screening we suggest nodule measurements by semi-automated volumetry should be used. Differences between volume and diameter based nodule management protocol in terms of early lung cancer detection, morbidity, mortality, radiation exposure and costs remain to be demonstrated.Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
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MO11 - Screening and Epidemiology (ID 131)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Imaging, Staging & Screening
- Presentations: 1
- Moderators:P. Zimmerman, J. Bowden
- Coordinates: 10/28/2013, 16:15 - 17:45, Bayside 201 - 203, Level 2
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MO11.05 - DISCUSSANT (ID 3993)
16:35 - 16:45 | Author(s): M. Oudkerk
- Abstract
- Presentation
Abstract not provided
Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
