Comparing LungRADS and the McWilliams nodule malignancy score: which approach works best to select screen detected pulmonary nodules for more aggressive followup?

PURPOSE In 2014 LungRADS was published to standardize CT lung screening reporting and management, based on nodule type, size, and growth. In 2013 the McWilliams model was published providing a nodule malignancy probability based on nodule size, type, morphology and subject characteristics. Threshold of the McWilliams score provides an alternative over LungRADS categories to determine workup for screendetected nodules. We compare both approaches on an independent data set. METHOD AND MATERIALS All 60 cancers were selected from the Danish Lung Cancer Screening Trial, in the first scan where they were visible, and 120 randomly selected benign nodules from baseline scans were added, all from different participants. Data had been acquired using a lowdose (16x0.75mm, 120kVp, 40mAs) protocol, and 1mm section thickness reconstruction. For each nodule, the malignancy probability was calculated using McWilliams model 2b. Parameters were available from the screening database or scored by an expert radiologist. Completely calcified nodules and perifissural nodules were given a score of 0, in accordance with the McWilliams model. All nodules were categorized into their LungRADS category based on nodule type and diameter. Perifissural nodules were treated as regular solid nodules, inaccordance with LungRADS guidelines. Sensitivity and specificity were calculated, for each LungRADS category cutoff. For each specificity level, corresponding sensitivity of the McWilliams model was determined. RESULTS McWilliams performed substantially better than LungRADS in selecting malignant nodules for more aggressive followup. Defining LungRADS category 2/3/4A/4B and up as a positive screening result, nodule malignancy specificity was 21%/65%/86%/99% and sensitivity was 100%/85%/58%/32%. At the same specificities, McWilliamsAC/a,!a,,C/s sensitivity was higher with 100%/96%/86%/45%. CONCLUSION For every cutoff level in LungRADS, the McWilliams model operating at the same specificity has superior sensitivity to differentiate malignant from benign nodules. CLINICAL RELEVANCE/APPLICATION The McWilliams model seems to be a better tool than LungRADS to provide a malignancy risk and help radiologists determine which subgroup of nodules detected in a screening setting need more invasive workup.