Lung cancer screening with low-dose CT: definition of positive, indeterminate, and negative screen results. A nodule management recommendation from the European Society of Thoracic Imaging

Abstract

Early detection of lung cancer through low-dose CT lung cancer screening in a high-risk population has proven to reduce lung cancer-specific mortality. Nodule management plays a pivotal role in early detection and further diagnostic approaches. The European Society of Thoracic Imaging (ESTI) has established a nodule management recommendation to improve the handling of pulmonary nodules detected during screening. For solid nodules, the primary method for assessing the likelihood of malignancy is to monitor nodule growth using volumetry software. For subsolid nodules, the aggressiveness is determined by measuring the solid part. The ESTI-recommendation enhances existing protocols but puts a stronger focus on lesion aggressiveness. The main goals are to minimise the overall number of follow-up examinations while preventing the risk of a major stage shift and reducing the risk of overtreatment. KEY POINTS: Question Assessment of nodule growth and management according to guidelines is essential in lung cancer screening. Findings Assessment of nodule aggressiveness defines follow-up in lung cancer screening. Clinical relevance The ESTI nodule management recommendation aims to reduce follow-up examinations while preventing major stage shift and overtreatment.

Keywords: Artificial intelligence; Low-dose computed tomography; Lung cancer; Pulmonary nodule; Screening programs (diagnostic).

Fig. 1

Suspicious morphological sign of ‘atypical cyst’ or ’cystic airspace’ in two patients. A, B Low-dose coronal CT images showing a 7-mm solid nodule in the wall of a right upper lobe cyst in a 60-year-old woman who smoked 31 pack-years, corresponding to an invasive adenocarcinoma staged pT1bN0R0. Standard-dose CT acquisition (B) performed preoperatively revealed a ground-glass component that was not detected on low-dose acquisition (A). C, D Low-dose axial CT images showing an atypical cyst of the left lower lobe in a 62-year-old woman with a smoking history of 40 pack-years. A solid part of 12 mm is extrinsically developed. A pT1b invasive adenocarcinoma was confirmed postoperatively

Fig. 2

Suspicious morphological signs of ‘bubble-like lucencies’ and/or ‘air bronchogram’ in four patients. A, B Low-dose axial CT images showing a 17-mm part-solid nodule of the right lower lobe with an anterior ground-glass component (A) and bubble-like lucencies (A, B), in a 69-year-old woman who smoked 50 pack-years. Since the nodule has a solid component that is larger than 80% of the whole nodule, according to the ESTI guidelines, it would be managed as a solid nodule. A pT1bN0R0 invasive adenocarcinoma was confirmed postoperatively. C, D Low-dose axial CT images showing a part-solid nodule of the right upper lobe with a 7-mm solid component and bubble-like lucencies in a 64-year-old woman who smoked 35 pack-years. A pT1cN0R0 invasive adenocarcinoma was confirmed postoperatively. E, F Low-dose axial CT images in soft kernel (E) and high frequency kernel (F) showing a part-solid nodule of the right upper lobe with small non-measurable solid components and central bubble-like lucency in a 54-year-old woman with a smoking history of 35 pack-years. The high-frequency kernel image (F) is noisier. A pT1bN0R0 invasive adenocarcinoma was confirmed postoperatively. G, H Low-dose sagittal CT images showing a 24-mm part-solid nodule of the right lower lobe with an air bronchogram (G) and bubble-like lucency (H), in a 52-year-old woman with a smoking history of 30 pack-years. A pT1bN0R0 invasive adenocarcinoma was confirmed postoperatively

Fig. 3

Suspicious morphological signs of ‘pleural indentation’ and ‘concave margin’ in two small invasive adenocarcinomas. A, B Low-dose axial CT images showing a part-solid nodule in the right lower lobe of a 57-year-old woman who had smoked 58 pack-years. Although still small, the nodule shows signs of pleural indentation. Histopathological examination confirmed the presence of an invasive adenocarcinoma with pleural invasion. The tumour was staged pT2N0R0. C, D Low-dose axial CT images showing a non-solid nodule of the right lower lobe in a 71-year-old man with a smoking history of 57 pack-years. The nodule shows a concave margin in the anterior aspect (C), then grows in size and density after 1 year (D)

Fig. 4

Flowchart for management of solid nodules detected at baseline. M = suspicious morphology upgrades risk to next category: spiculation, architectural distortion (pleural tag, fissural displacement), cystic component, bubble-like lucencies, concave sign, narrowed vessels. Benign morphology: calcification (central, diffuse, popcorn-like), fat components, typical intrapulmonary lymph node morphology (smooth margins, oval, lentiform, or triangular shape, < 1 cm, distance to pleura < 1 cm, under the carina). Growth = substantial growth, defined as follows: • If volumetry is possible: VDT < 250 days at 3 months, VDT < 400 days at 6 months and VDT < 500 days at ≥ 12 months. • If volumetry fails: visually verifiable increase in average diameter of > 1.5 mm over a time interval of maximally 1 year, or substantial change in morphology. A decrease in size may indicate a benign process (inflammation, infection, other) and prompts ongoing follow-up to ensure shrinkage continues. ΔD = change in effective diameter relative to baseline, derived from volume or from manual measurements if volumetry fails. MDT = multidisciplinary team decision is advised if the effective diameter of a slow-growing nodule increases by more than 5 mm from baseline

Fig. 5

Flowchart for management of subsolid nodules detected at baseline. M = suspicious morphology upgrades risk to next category: spiculation, architectural distortion (pleural tag, fissure displacement), cystic component, bubble-like lucencies, concave sign, bronchus cut-off, ground glass component ≥ 3 cm in average or effective diameter. Solid component: if the solid component of a part-solid nodule is more than 80% of the entire nodule diameter, this nodule should be classified as a solid nodule. Growth = substantial growth, defined as follows: • If volumetry is possible: VDT < 250 days at 3 months, VDT < 400 days at 6 months and VDT < 500 days at ≥ 12 months. • If volumetry fails: visually verifiable increase in average diameter of > 1.5 mm over a time interval of maximally 1 year, or substantial change in morphology. Regression = complete disappearance or marked decrease in size, density or volume of subsolid nodules. ΔD = change in effective diameter relative to baseline, derived from volume or from manual measurements if volumetry fails. MDT = multidisciplinary team decision is advised if the effective diameter of a slow-growing nodule increases by more than 5 mm from baseline

Fig. 6

Flowchart for management of new nodules. New nodules that had been missed or not reported on previous scans are managed according to the same rules as nodules found at baseline