RadioGraphics Update: The 10 Pillars of Lung Cancer Screening-Rationale and Logistics of a Lung Cancer Screening Program.

Editor's Note.-RadioGraphics Update articles supplement or update information found in full-length articles previously published in RadioGraphics. These updates, written by at least one author of the previous article, provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes.

Lung-RADS Category 3 and 4 Nodules on Lung Cancer Screening in Clinical Practice.

BACKGROUND. Lung-RADS category 3 and 4 nodules account for most screening-detected lung cancers and are considered actionable nodules with management implications. The cancer frequency among such nodules is estimated in the Lung-RADS recommendations and has been investigated primarily by means of retrospectively assigned Lung-RADS classifications. OBJECTIVE. The purpose of this study was to assess the frequency of cancer among lung nodules assigned Lung-RADS category 3 or 4 at lung cancer screening (LCS) in clinical practice and to evaluate factors that affect the cancer frequency within each category. METHODS. This retrospective study was based on review of clinical radiology reports of 9148 consecutive low-dose CT LCS examinations performed for 4798 patients between June 2014 and January 2021 as part of an established LCS program. Unique nodules assigned Lung-RADS category 3 or 4 (4A, 4B, or 4X) that were clinically categorized as benign or malignant in a multidisciplinary conference that considered histologic analysis and follow-up imaging were selected for further analysis. Benign diagnoses based on stability required at least 12 months of follow-up imaging. Indeterminate nodules were excluded. Cancer frequencies were evaluated. RESULTS. Of the 9148 LCS examinations, 857 (9.4%) were assigned Lung-RADS category 3, and 721 (7.9%) were assigned category 4. The final analysis included 1297 unique nodules in 1139 patients (598 men, 541 women; mean age, 66.0 ± 6.3 years). A total of 1108 of 1297 (85.4%) nodules were deemed benign, and 189 of 1297 (14.6%) were deemed malignant. The frequencies of malignancy of category 3, 4A, 4B, and 4X nodules were 3.9%, 15.5%, 36.3%, and 76.8%. A total of 45 of 46 (97.8%) endobronchial nodules (all category 4A) were deemed benign on the basis of resolution. Cancer frequency was 13.1% for solid, 24.4% for part-solid, and 13.5% for ground-glass nodules. CONCLUSION. In the application of Lung-RADS to LCS clinical practice, the frequency of Lung-RADS category 3 and 4 nodules and the cancer frequency in these categories were higher than the prevalence and cancer risk estimated for category 3 and 4 nodules in the Lung-RADS recommendations and those reported in earlier studies in which category assignments were retrospective. Nearly all endobronchial category 4A nodules were benign. CLINICAL IMPACT. Future Lung-RADS iterations should consider the findings of this study from real-world practice to improve the clinical utility of the system.

Longitudinal CT and MRI Characteristics of Unilocular Thymic Cysts.

Background Isoattenuating and hyperattenuating thymic cysts at CT are often misinterpreted as lymphadenopathy or thymic epithelial neoplasms. Purpose To evaluate the longitudinal change in thymic cyst appearance at CT and MRI. Materials and Methods All chest MRI studies showing thymic cysts between July 2008 and December 2019, identified from a retrospective search of a quality assurance database, were included in this study if initial CT depicted a thymic lesion, the patient was referred for follow-up MRI for characterization, and the baseline (ie, index) MRI indicated a cystic lesion. Follow-up CT scans and/or MRI scans were identified through July 2020. Thymic cyst characteristics, such as size, location, and morphologic features, as well as CT and MRI characteristics, were recorded. Change in size, attenuation, and T1-weighted MRI signal was assessed longitudinally. Descriptive statistics of longitudinal change were tabulated. Results A total of 244 chest MRI studies in 140 patients with 142 unique cysts and 392 CT examinations (636 total examinations and 645 thymic cysts-nine examinations with two cysts each) were evaluated. The median follow-up duration was 2.2 years. Thirty-three patients with 34 unique cysts (34 of 142 cysts [24%]) underwent imaging follow-up for more than 5 years. Thymic cysts followed up for more than 5 years were most commonly saccular (189 of 274 cysts [69% axially]) and retrosternal (14 of 34 cysts [41%]). Craniocaudal dimension was larger than transverse and anteroposterior dimensions in 223 of 274 cysts (81%). Mean thymic cyst attenuation was 25 HU (range, 15-100 HU). Five of 31 cysts (16%) exhibited wall calcification. The median cyst wall thickness was 2.0 mm (range, 0.9-3.0 mm). Most thymic cysts changed in volume (31 of 34 cysts [91%]), CT attenuation (15 of 35 cysts [43%]), and T1-weighted MRI signal (12 of 18 cysts [67%]) over time. None developed mural irregularity, nodularity, or septations. Conclusion Unilocular thymic cysts, defined at index MRI, never developed irregular wall thickening, mural nodularity, or septations that would raise concern for malignant transformation. However, these cysts showed mural calcification and change in size, CT attenuation, and MRI signal over more than 5 years of follow-up. © RSNA, 2021 Online supplemental material is available for this article.

Racial and Ethnic Disparities in Lung Cancer Screening Eligibility.

Background To address disparities in lung cancer screening (LCS) that may exclude large numbers of high-risk African American smokers, revised U.S. Preventive Services Task Force (USPSTF) recommendations lowered LCS eligibility thresholds. However, there are limited recent data about the impact of newly revised guidelines on disparities in LCS eligibility. Purpose To evaluate the impact of revised USPSTF guidelines on racial and ethnic disparities in LCS eligibility. Materials and Methods Cross-sectional survey data from 20 states were retrospectively evaluated from the 2019 Behavioral Risk Factor Surveillance System survey (median response rate, 49.4%). Respondents without a history of lung cancer aged 55-79 years (ie, under the previous guidelines) or aged 50-79 years (ie, under the revised guidelines) were included. Multivariable logistic regression analyses were performed to evaluate the association between race and ethnicity and LCS eligibility. All analyses were performed accounting for complex survey design features (ie, weighting, stratification, and clustering). Results Under previous guidelines, 11% of 67 567 weighted survey respondents were eligible for LCS (White [12%], Hispanic [4%], African American [7%], American Indian [17%], Asian or Pacific Islander [4%], and other [12%]). Under revised USPSTF guidelines, 14% of 77 689 weighted survey respondents were eligible for LCS (White [15%], Hispanic [5%], African American [9%], American Indian [21%), Asian or Pacific Islander [5%], and other [18%]). Compared with White respondents, African American respondents (adjusted odds ratio [OR] = 0.36; 95% CI: 0.27, 0.47; P < .001) and Hispanic respondents (adjusted OR = 0.15; 95% CI: 0.09, 0.24; P < .001) were less likely to be eligible for LCS under previous guidelines. African American respondents (adjusted OR = 0.39; 95% CI: 0.32, 0.47; P < .001) and Hispanic respondents (adjusted OR = 0.15; 95% CI: 0.10, 0.23; P < .001) were less likely to be eligible under the revised guidelines. The Wald test showed no evidence of differences in the degree to which racial and ethnic minority groups were less likely to be eligible for LCS when comparing previous versus revised USPSTF guidelines (P = .76). Conclusion The revised U.S. Preventive Services Task Force guidelines (version 2.0) may perpetuate lung cancer disparities, as racial and ethnic minority groups are still less likely to be eligible for lung cancer screening. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Jacobs and Springfield in this issue.

PET/MRI assessment of lung nodules in primary abdominal malignancies: sensitivity and outcome analysis.

PURPOSE: To evaluate PET/MR lung nodule detection compared to PET/CT or CT, to determine growth of nodules missed by PET/MR, and to investigate the impact of missed nodules on clinical management in primary abdominal malignancies. METHODS: This retrospective IRB-approved study included [18F]-FDG PET/MR in 126 patients. All had standard of care chest imaging (SCI) with diagnostic chest CT or PET/CT within 6 weeks of PET/MR that served as standard of reference. Two radiologists assessed lung nodules (size, location, consistency, position, and [18F]-FDG avidity) on SCI and PET/MR. A side-by-side analysis of nodules on SCI and PET/MR was performed. The nodules missed on PET/MR were assessed on follow-up SCI to ascertain their growth (≥ 2 mm); their impact on management was also investigated. RESULTS: A total of 505 nodules (mean 4 mm, range 1-23 mm) were detected by SCI in 89/126 patients (66M:60F, mean age 60 years). PET/MR detected 61 nodules for a sensitivity of 28.1% for patient and 12.1% for nodule, with higher sensitivity for > 7 mm nodules (< 30% and > 70% respectively, p < 0.05). 75/337 (22.3%) of the nodules missed on PET/MR (follow-up mean 736 days) demonstrated growth. In patients positive for nodules at SCI and negative at PET/MR, missed nodules did not influence patients' management. CONCLUSIONS: Sensitivity of lung nodule detection on PET/MR is affected by nodule size and is lower than SCI. 22.3% of missed nodules increased on follow-up likely representing metastases. Although this did not impact clinical management in study group with primary abdominal malignancy, largely composed of extra-thoracic advanced stage cancers, with possible different implications in patients without extra-thoracic spread.

Clinicopathologic and Longitudinal Imaging Features of Lung Cancer Associated With Cystic Airspaces: A Systematic Review and Meta-Analysis.

BACKGROUND. Lung cancer (LC) associated with cystic airspaces is an uncommon presentation that is underrecognized on imaging. Additionally, understanding of its underlying pathology and risk factors is limited, which can contribute to delays in diagnosis. OBJECTIVE. The purpose of this analysis was to systematically review, analyze, and synthesize the medical literature to determine the imaging features of LC associated with cystic airspaces. EVIDENCE ACQUISITION. In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included published research reporting the clinical, pathologic, and imaging features of LC associated with cystic airspaces. We then performed a pooled analysis of continuous and categoric data with respect to patient clinical characteristics, tumor pathologic features, underlying driver mutation, CT features, and evolution of these features over time. EVIDENCE SYNTHESIS. The analysis included eight original observational studies with a combined total of 341 patients with LC associated with cystic airspaces (weighted mean age, 61.8 years; range, 30-87 years; 135 women and 206 men). Most patients were current or previous smokers (127/192 [66.1%]). The most common histologic finding was adenocarcinoma (289/328 [88.1%]) followed by squamous cell carcinoma (30/328 [9.1%]). The most common driver mutations were EGFR (46/122 [37.7%]) and KRAS (21/122 [17.2%]). The cysts in LC associated with cystic airspaces commonly had nonuniform (104/114 [91.2%]) and thick (83/222 [37.4%]) walls, irregular margins (53/142 [37.3%]), and were unilocular (173/272 [63.6%]). Most cysts had a nodular component (210/328 [64.0%]). Over time, most cysts showed development or enlargement of the nodular component (61/89 [68.5%]), approximately half showed wall thickening (43/89 [48.3%]), and a minority evolved into completely solid lesions (11/89 [12.4%]). The size of the cystic component increased in 36 of 89 patients (40.4%), decreased in 28 (31.5%), and remained stable in 24 (27.0%). CONCLUSION. LC associated with cystic airspaces occurs most commonly as adeno-carcinoma and is seen in both smokers and nonsmokers. The cysts associated with LC show wall thickening and mural nodularity, which may evolve over time. LC associated with cystic airspaces can be indolent, and long-term surveillance with imaging should be considered if cysts are not resected. CLINICAL IMPACT. Familiarity with the imaging features and temporal evolution of LC associated with cystic airspaces can minimize delays in LC diagnosis. Future management guidelines should include protocols for follow-up and management of cystic lung lesions identified during diagnostic and LC screening CT.

Management and Outcomes of Suspected Infectious and Inflammatory Lung Abnormalities Identified on Lung Cancer Screening CT.

BACKGROUND. Incidental findings are frequently encountered during lung cancer screening (LCS). Limited data describe the prevalence of suspected acute infectious and inflammatory lung processes on LCS and how they should be managed. OBJECTIVE. The purpose of this study was to determine the prevalence, radiologic reporting and management, and outcome of suspected infectious and inflammatory lung processes identified incidentally during LCS and to propose a management algorithm. METHODS. This retrospective study included 6314 low-dose CT (LDCT) examinations performed between June 2014 and April 2019 in 3800 patients as part of an established LCS program. Radiology reports were reviewed, and patients with potentially infectious or inflammatory lung abnormalities were identified and analyzed for descriptors of imaging findings, Lung-RADS designation, recommendations, and clinical outcomes. Using the descriptors, outcomes, and a greater than 2% threshold risk of malignancy, a follow-up algorithm was developed to decrease additional imaging without affecting cancer detection. RESULTS. A total of 331/3800 (8.7%) patients (178 men, 153 women; mean age [range], 66 [53-87] years) undergoing LCS had lung findings that were attributed to infection or inflammation. These abnormalities were reported as potentially significant findings using the S modifier in 149/331 (45.0%) and as the dominant nodule used to determine the Lung-RADS category in 96/331 (29.0%). Abnormalities were multiple or multifocal in 260/331 (78.5%). Common descriptors were ground-glass (155/331; 46.8%), tree-in-bud (56/331; 16.9%), consolidation (41/331; 12.4%), and clustered (67/331; 20.2%) opacities. A follow-up chest CT outside of screening was performed within 12 months or less in 264/331 (79.8%) and within 6 months or less in 186/331 (56.2%). A total of 260/331 (78.5%) opacities resolved on follow-up imaging. Two malignancies (2/331; 0.6%) were associated with these abnormalities and both had consolidations. Theoretic adoption of a proposed management algorithm for suspected infectious and inflammatory findings reduced unnecessary follow-up imaging by 82.6% without missing a single malignancy. CONCLUSION. Presumed acute infectious or inflammatory lung abnormalities are frequently encountered in the setting of LCS. These opacities are commonly multifocal and resolve on follow-up. Less than 1% are associated with malignancy. CLINICAL IMPACT. Adoption of a conservative management algorithm can standardize recommendations and reduce unnecessary imaging without increasing the risk of missing a malignancy.

Barriers to Lung Cancer Screening Engagement from the Patient and Provider Perspective.

Lung cancer remains the leading cause of cancer mortality in the United States. Lung cancer screening (LCS) with low-dose CT reduces mortality among high-risk current and former smokers and has been covered by public and private insurers without cost sharing since 2015. Patients and referring providers confront numerous barriers to participation in screening. To best serve in multidisciplinary efforts to expand LCS nationwide, radiologists must be knowledgeable of these challenges. A better understanding of the difficulties confronted by other stakeholders will help radiologists continue to collaboratively guide the growth of LCS programs in their communities. This article reviews barriers to participation in LCS for patients and referring providers, as well as possible solutions and interventions currently underway.

Image-guided Preoperative Localization of Pulmonary Nodules for Video-assisted and Robotically Assisted Surgery.

Video-assisted thoracic surgery (VATS) and robotically assisted surgery are used increasingly for minimally invasive diagnostic and therapeutic resection of pulmonary nodules. Unsuccessful localization of small, impalpable, or deep pulmonary nodules can necessitate conversion from VATS to open thoracotomy. Preoperative localization techniques performed by radiologists have improved the success rates of VATS resection for small and subsolid nodules. Any center at which VATS diagnostic resection of indeterminate pulmonary nodules is performed should be supported by radiologists who offer preoperative nodule localization. Many techniques have been described, including image-guided injection of radioisotopes and radiopaque liquids and placement of metallic wires, coils, and fiducial markers. These markers enable the surgeon to visualize the position of an impalpable nodule intraoperatively. This article provides details on how to perform each percutaneous localization technique, and a group of national experts with established nodule localization programs describe their preferred approaches. Special reference is made to equipment required, optimization of marker placement, prevention of technique-specific complications, and postprocedural treatment. This comprehensive unbiased review provides valuable information for those who are considering implementation or optimization of a nodule localization program according to workflow patterns, surgeon preference, and institutional resources in a particular center. ©RSNA, 2019.

Postoperative Imaging After Lobectomy: Predicting the Displacement and Change in Orientation of Nonresected Lung Nodules.

OBJECTIVES: The objective of this study was to determine the effect of a lobectomy to the location and orientation of nonresected lung nodule and its corresponding airway. METHODS: We reviewed preoperative and postoperative computed tomography of patients who underwent lobectomies and have a separate nonresected nodule in the ipsilateral lung. Displacement of the nonresected nodule and angulation of its corresponding segmental bronchus were measured. RESULTS: Fifty nodules from 40 patients (30 females, 10 male; mean ± SD age, 67 ± 7 years) were assessed. Nodules are displaced clockwise after right upper, right middle, and left lower lobectomies and counterclockwise after right lower and left upper lobectomies. Displacement of the remaining nodules was greater in the craniocaudal plane, followed by anteroposterior and transverses planes (mean, 3.7, 2.5, and 1.9 cm, respectively). CONCLUSIONS: Remaining ipsilateral nodules and their associated segmental airways are displaced in a predictable fashion after lobectomy. This may help in the assessment of follow-up imaging.

Imaging and Management of Intrathoracic Renal Cell Carcinoma Metastases.

OBJECTIVE: Renal cell carcinoma (RCC) has a propensity to metastasize to the chest, with the lungs being the most common distant metastatic site. The histologic subtype of RCC has implications for prognosis. CONCLUSION: Significant advances have been made in the management of metastatic RCC, both in systemic and locoregional therapies. The aim of this article is to review appearances of intrathoracic metastases from RCC and to discuss treatment considerations.

Fluorodeoxyglucose positron emission tomography for detection of tumor recurrence following radiofrequency ablation in retrospective cohort of stage I lung cancer.

PURPOSE: The goal of this study was to define patterns for tumor recurrence on PET following RFA, compare time to imaging recurrence by PET versus CT, evaluate whether pre-treatment tumor uptake predicts recurrence and propose an optimal post-RFA surveillance strategy. MATERIALS AND METHODS: A retrospective cohort study was performed of biopsy confirmed primary stage I lung cancers treated with RFA. FDG PET and near contemporaneous diagnostic CT imaging pre-ablation, within 30 days post-ablation, and beyond 6 months were independently and retrospectively evaluated for features supportive of recurrence. Time to imaging recurrence by PET (TTR_PET) and by CT (TTR_CT) were determined and compared. FDG avidity of untreated tumors was compared between recurrent and non-recurrent groups. RESULTS: Thirteen recurrences after 72 RFA treatments were confirmed by diagnostic CT. All recurrences were associated with focally intense and increasing FDG uptake beyond 6 months (sensitivity 100%; specificity 98.5%). Mean TTR_PET was 14 months compared to mean TTR_CT of 17 months (not statistically significant). Normalized SUVmax and total lesions glycolysis of lung cancers that recurred after RFA was 4.0 and 6.0, respectively compared to 2.8 and 5.0, respectively for cancers that did not recur (p = .068). CONCLUSION: A pattern of focally intense and increasing FDG PET uptake has high sensitivity and specificity for detecting recurrent lung cancer following RFA. Surveillance after RFA should include a contrast enhanced diagnostic CT at 1 month to diagnose procedural complications, PET at 6 months as a post-treatment metabolic baseline (with diagnostic CT if PET is abnormal) and alternating diagnostic CTs or PET every 6 months for 2 years.

Should Dual-Energy Computed Tomography Pulmonary Angiography Replace Single-Energy Computed Tomography Pulmonary Angiography in Pregnant and Postpartum Patients?

OBJECTIVE: The study aims to compare single-energy (SE) and dual-energy (DE) computed tomography pulmonary angiography (CTPA) for evaluation of suspected pulmonary embolism in pregnant and postpartum patients. MATERIALS AND METHODS: Our study included 59 CTPA performed in pregnant/postpartum women (study group) comprised of 38 SE-CTPA and 21 DE-CTPA. The control group of 21 age- and weight-matched nonpregnant/nonpostpartum women underwent DE-CTPA. Two radiologists assessed pulmonary arterial enhancement, image quality, and artifacts. κ Test and analysis of variance were performed. RESULTS: Fourteen of 38 pregnant/postpartum women (37%) had suboptimal SE-CTPA compared with just 10% (2/21) suboptimal DE-CTPA studies (P = 0.02). Mean Hounsfield unit (HU) in the pulmonary trunk was 550 ± 68 HU in the DE-CTPA pregnant/postpartum group and 245 ± 12 HU in the SE-CTPA (P < 0.001). The mean volume computed tomography dose index in the pregnant/postpartum patients for DE-CTPA and SE-CTPA were 9 ± 2 and 19 ± 8 mGy, respectively (P < 0.001). CONCLUSIONS: Dual-energy CTPA substantially increased arterial enhancement for evaluation of pulmonary embolism in pregnant and postpartum women compared with SE-CTPA.