5-year lung cancer screening experience: growth curves of 18 lung cancers compared to histologic type, CT attenuation, stage, survival, and size

Growth characteristics of early-stage (IA) lung adenocarcinoma and its value in predicting lymph node metastasis

BACKGROUND

We aim to compare the differences in growth characteristics between part-solid and solid lung adenocarcinoma, and to investigate the value of volume doubling time (VDT) or mass doubling time (MDT) in predicting lymph node (LN) metastasis and preoperative evaluation in patients of early-stage (IA) non-small cell lung cancer (NSCLC).

METHOD

We reviewed 8,653 cases of surgically resected stage IA lung adenocarcinoma between 2018 and 2022, with two follow-up visits at least 3 months apart, comparing diameter, volume, and mass growth of pSN and SN. VDT and MDT calculations for nodules with a volume change of at least 25%. Univariable or multivariable analysis was used to identify the risk factors. The area under the curve (AUC) for the receiver operating characteristic (ROC) curves was used to evaluate the diagnostic value.

RESULTS

A total of 144 patients were included 114 with solid nodules (SN) and 25 with part-solid nodules (pSN). During the follow-up period, the mean VDTt and MDTt of SN were shorter than those of pSN, 337 vs. 541 days (p = 0.005), 298 vs. 458 days (p = 0.018), respectively. Without considering the ground-glass component, the mean VDTc and MDTc of SN were shorter than the solid component of pSN, 337 vs. 498 days (p = 0.004) and 298 vs. 453 days (p = 0.003), respectively. 27 nodules were clinically and pathologically diagnosed as N1/N2. Logistic regression identified initial diameter (p < 0.001), consolidation increase (p = 0.019), volume increase (p = 0.020), mass increase (p = 0.021), VDTt (p = 0.002), and MDTt (p = 0.004) were independent factors for LN metastasis. The ROC curves showed that the AUC for VDTt was 0.860 (95% CI, 0.778-0.943; p < 0.001) and for MDTt was 0.848 (95% CI, 0.759-0.936; p < 0.001).

CONCLUSIONS

Our study showed significant differences in the growth characteristics of pSN and SN, and the application of VDT and MDT could be a valid predictor LN metastasis in patients with early-stage NSCLC.

Prognostic impact of highly solid component in early-stage solid lung adenocarcinoma

Background

Based on computed tomography (CT) findings of lung cancer, solid nodules have a much worse prognosis than subsolid nodules, even if the nodules are subcentimeter in size. There is, however, no systematic method for determining the prognosis of solid tumors on CT. This study aimed to discover the prognostic factor of early-stage solid lung adenocarcinoma using three-dimensional CT volumetry.

Methods

Patients with pathological stage I solid lung adenocarcinoma who underwent complete resection between 2007 and 2012 were selected in this retrospective study. Clinicopathological data and preoperative multidetector CT findings, such as tumor size on the two-dimensional axial image, three-dimensional tumor volume between -600 and 199 HU, and three-dimensional solid volume between 0 and 199 HU, which corresponded to highly solid components, were compared between recurrence and non-recurrence. Furthermore, these radiological values were compared to pathological invasive volume (PIV).

Results

During this time, 709 patients had their lung cancer completely removed. From this cohort, 90 patients with pathological stage I solid lung adenocarcinoma were selected. In addition, recurrence was found in 26 patients (28.9%). Although two-dimensional axial image, serum carcinoembryonic antigen (CEA) level, and SUVmax on 18F fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) did not differ statistically between recurrent and non-recurrent patients, three-dimensional tumor and solid tumor volume did. Multivariate analysis indicated that three-dimensional solid tumor volume [hazard ratio: 2.440; 95% confidence interval (CI): 1.110-5.361, P=0.026] and epidermal growth factor receptor (EGFR) mutation (hazard ratio: 4.307; 95% CI: 1.328-13.977, P=0.015) were significantly associated with disease-free survival (DFS). When three-dimensional tumor and solid tumor volume were compared to PIV, three-dimensional solid tumor volume (3,091 mm3 on average) showed a highly similar value with PIV (2,930 mm3 on average), whereas three-dimensional tumor volume (6,175 mm3 on average) was significantly larger than PIV (P<0.001).

Conclusions

In patients with early-stage solid lung adenocarcinoma, the measurement of three-dimensional solid tumor volume, which is correlated with PIV, accurately predicted the postoperative outcome.

Indeterminate pulmonary subsolid nodules in patients with no history of cancer: growing prediction, CT pattern, and pathological diagnosis

PURPOSE We aimed to evaluate and compare the growth patterns among pathological types of inde- terminate subsolid nodules in patients without a history of cancer as observed on computed tomography (CT). METHODS This retrospective study included 77 consecutive patients with 80 indeterminate subsolid nod- ules on unenhanced thin-section CT. Subsolid nodules were classified into 2 growth pattern groups based on volume: growth (n = 35) and non-growth (n = 42). According to the pathologi- cal diagnosis, subsolid nodules were further subdivided into 3 groups: adenocarcinoma in situ (growth, n = 8 vs. non-growth, n = 22), minimally invasive adenocarcinoma (n = 14 vs. n = 15), and invasive adenocarcinoma (n=13 vs. n=5). Kaplan-Meier and Cox proportional hazards regres- sion analyses were performed to identify the risk factors for subsolid nodules growth. The CT findings of the 35 subsolid nodules in the growth group were compared among the 3 pathologi- cal groups. RESULTS In the growth group, the overall mean volume doubling time and mass doubling time (MDT) were 811.5 days and 616.5 days, respectively. Patient's age (odds ratio=1.041, P=.045) and CT subtype of non-solid nodule and part-solid nodule (odds ratio=3.430, P=.002) could predict subsolid nodule growth. The baseline volume, mass, and mean CT value were larger in the inva- sive adenocarcinoma group than in the adenocarcinoma in situ group (all P < .01). The shortest volume doubling time was observed in the invasive adenocarcinoma group, followed by the minimally invasive adenocarcinoma group and the adenocarcinoma in situ group. A shorter mass doubling time was observed in the minimally invasive adenocarcinoma group than in the adenocarcinoma in situ group (all P < .02). CONCLUSION As age increases, the risk of pulmonary subsolid nodule growth increases by 4% each year, and part-solid nodules have a 3 times higher risk of growth compared to non-solid nodules in patients with no history of cancer. Subsolid nodules with more aggressive pathological charac- teristics grow at a faster rate.

Dynamic Observation of Lung Nodules on Chest CT Before Diagnosis of Early Lung Cancer

Objective

Early recognition and diagnosis of lung cancer can help improve the prognosis of patients. However, early imaging patterns of malignant lung nodules are not fully clear. To understand the early imaging signs of malignant lung cancer nodules, the changes of the lung nodules before diagnosis were dynamically observed and analyzed.

Materials and Methods

This retrospective study observed dynamic changes of lung nodules before pathological confirmation with consecutive regular chest CT examination from January 2003 to December 2018. At least 3 follow-up CT scans were performed in all cases, and the interval between each follow-up was about 1 year. The size, density, and morphological signs of the nodules were evaluated based on the CT axial image, and a reverse line chart or scatter plot with the diagnosis time as coordinate origin was constructed.

Results

A total of 55 lung nodules in 53 patients (mean age, 58.40 years ±11.43 [standard deviation]; 20 women) were accessed. The follow-up time was 5.96 ± 2.68 years. The average diameters in maximum slice of the lesion at baseline and last scan were 6.83 ± 2.92 mm and 16.65 ± 7.34 mm, respectively. According to the reverse line chart, the nodule growth curve segments within 4 years from the last scan showed an ascending shape, and those beyond 4 years showed a flat shape. There are 90.9% (50/55) GGN and 9.1% (5/55) SN when the lesion first appears, and 21.8% (12/55) GGN, 38.2% (21/55) PSN, and 40% (22/55) SN in the last scan. There are 12.7% (7/55) and 98.2% (54/55) nodules with poor morphological signs at baseline and last scan, respectively.

Conclusion

At the time node close to the diagnosis, the growth curve showed an upward pattern; the proportion of PSN and SN rose as the main density types; and the appearance of poor morphological signs of nodules increased. When a persistent lung nodule starts to show a malignant change, a further diagnostic workup is warranted.

Preoperative Changes of Lung Nodule on Computed Tomography and Their Relationship With Pathological Outcomes

Background

Whether changes of lung nodules on computed tomography could bring us helpful information related to their pathological outcomes remained unclear.

Materials and Methods

This retrospective study was carried out among 1,185 cases of lung nodules in Shanghai Chest Hospital from January 2015 to April 2017, which did not shrink or disappear after preoperative follow-up over three months. Their imaging features, changes, and clinical characteristics were collected. A separate analysis was performed in nodules with or without growth in long-axis diameter after follow-up, searching significant changes related to nodule malignancy and the median interval of follow-up for reference. Further study was performed similarly in malignant nodules for discrimination of malignant grading.

Results

Most nodules were stable (n = 885, 75%), whereas others grew (n = 300, 25%). For predicting nodule malignancy, increase in density (&gt;10 Hounsfield units, median follow-up of 549 days) played an important role in growing group whereas it failed in stable group, and the increase in size was less significant in growing group. For discrimination of malignant grading, increase in density (&gt;70 Hounsfield units, median follow-up of 366 days) showed its significance in stable group, and so did increase in size in growing group (maximum diameter growth &gt;3.3 mm, median follow-up of 549 days, or average diameter growth &gt;3.1 mm, median follow-up of 625 days).

Conclusions

There were significant changes of lung nodules by follow-up on computed tomography, related to their pathological outcomes. The predictive power of increase in density or size varied in different situations, whereas all referred to a long-time preoperative follow-up.

A predictive nomogram for two-year growth of CT-indeterminate small pulmonary nodules

OBJECTIVES

Lung cancer is the most common cancer and the leading cause of cancer-related death worldwide. The optimal management of computed tomography (CT)-indeterminate pulmonary nodules is important. To optimize individualized follow-up strategies, we developed a radiomics nomogram for predicting 2-year growth in case of indeterminate small pulmonary nodules.

METHODS

A total of 215 histopathology-confirmed small pulmonary nodules (21 benign and 194 malignant) in 205 patients with ultra-high-resolution CT (U-HRCT) were divided into growth and nongrowth nodules and were randomly allocated to the primary (n = 151) or validation (n = 64) group. The least absolute shrinkage and selection operator (LASSO) method was used for radiomics feature selection and radiomics signature determination. Multivariable logistic regression analysis was used to develop a radiomics nomogram that integrated the radiomics signature with significant clinical parameters (sex and nodule type). The area under the curve (AUC) was applied to assess the predictive performance of the radiomics nomogram. The net benefit of the radiomics nomogram was assessed using a clinical decision curve.

RESULTS

The radiomics signature and nomogram yielded AUCs of 0.892 (95% confidence interval [CI]: 0.843-0.940) and 0.911 (95% CI: 0.867-0.955), respectively, in the primary group and 0.826 (95% CI: 0.727-0.926) and 0.843 (95% CI: 0.749-0.937), respectively, in the validation group. The clinical usefulness of the nomogram was demonstrated by decision curve analysis.

CONCLUSIONS

A radiomics nomogram was developed by integrating the radiomics signature with clinical parameters and was easily used for the individualized prediction of two-year growth in case of CT-indeterminate small pulmonary nodules.

KEY POINTS

• A radiomics nomogram was developed for predicting the two-year growth of CT-indeterminate small pulmonary nodules. • The nomogram integrated a CT-based radiomics signature with clinical parameters and was valuable in developing an individualized follow-up strategy for patients with indeterminate small pulmonary nodules.

Differentiation of adenocarcinoma in situ with alveolar collapse from minimally invasive adenocarcinoma or invasive adenocarcinoma appearing as part-solid ground-glass nodules (≤ 2 cm) using computed tomography

PURPOSE

To investigate the differentiating computed tomographic (CT) features between adenocarcinoma in situ (AIS) with alveolar collapse and minimally invasive adenocarcinoma (MIA) or invasive adenocarcinoma (IA) appearing as part-solid nodules.

METHODS

A total of 147 consecutive patients with 157 pathology-confirmed part-solid ground-glass nodules (GGNs) ≤ 20 mm without other pathological condition such as inflammation and fibrosis who underwent chest CT were included.

RESULTS

The 157 part-solid GGNs included 33 (21.02%) pathologically confirmed AISs with alveolar collapse. Multivariate analysis revealed that smaller lesion size (odds ratio [OR] 0.671), and well-defined border (OR 5.544), concentrated distribution (OR 7.994), and homogeneity of the solid portion (OR 4.365) were significant independent predictors for differentiating AIS with alveolar collapse from MIA (P < 0.05) with excellent accuracy (area under receiver operating characteristic [ROC] curve, 0.902). Multivariate analysis revealed that smaller lesion size (OR 0.782), and size (OR 0.821), well-defined border (OR 5.752), and homogeneity of solid portion (OR 6.182) were significant independent predictors differentiating AIS with alveolar collapse from IA (P < 0.05) with excellent accuracy (area under ROC curve 0.910).

CONCLUSION

Among part-solid GGNs, AIS with alveolar collapse can be accurately differentiated from MIA on the basis of smaller lesion size, well-defined border, concentrated distribution, and homogeneity of solid portion, and from IA according to smaller lesion size, and smaller size, well-defined border, and homogeneity of solid portion.

Surgery or Non-surgical Treatment of ≤8 mm Non-small Cell Lung Cancer: A Population-Based Study

Background: Timing for intervention of small indeterminate pulmonary nodules has long been a topic of debate given the low incidence of malignancy and difficulty in obtaining a definite preoperative diagnosis. We sought to determine survival outcomes of surgical and non-surgical managements in non-small cell lung cancer (NSCLC) ≤8 mm, which may provide a reference for prospective decision-making for patients with suspected NSCLC. Method: A total of 1,652 patients with Stage IA NSCLC ≤8 mm were identified from the Surveillance, Epidemiology, and End Results (SEER) database and categorized into surgery and non-surgery groups. Chi-square test, t-test and Mann-Whitney U test were used to compare the baseline characteristics between groups. Survival curves were depicted using Kaplan-Meier method and compared by log-rank test. Cox proportional hazard model was used for univariate and multivariate analyses. Adjustment of confounding factors between groups was performed by propensity score matching. Results: The surgery and non-surgery groups included 1,438 and 208 patients, respectively. Patients in surgery group demonstrated superior survival outcome than patients in non-surgery group both before [overall survival (OS): HR, 16.22; 95% CI, 11.48-22.91, p < 0.001; cancer-specific survival (CSS): HR, 49.6; 95% CI, 31.09-79.11, p < 0.001] and after (OS: HR, 3.12; 95% CI, 2.40-4.05, p < 0.001; CSS: HR, 3.85; 95% CI, 2.74-5.40, p < 0.001) propensity score matching. The 30-day mortality rates were 3.1 and 12.0% in surgery and non-surgery groups, respectively. Multivariate analysis suggested age, sex, race, tumor size, grade, pathological stage were all independent prognostic factors in patients with ≤8 mm NSCLC. A comparison of surgical resections revealed a survival superiority of lobectomy over sub-lobectomy. In terms of CSS, no statistically significant difference was found between segmentectomy and wedge resection. Conclusion: The current SEER database showed better prognosis of surgical resection than non-surgical treatment in patients with ≤8 mm NSCLC. However, the factors that should be essentially included in the proper propensity-matched analysis, such as comorbidity, cardiopulmonary function and performance status were unavailable and the true superiority or inferiority should be examined further by ongoing randomized trial, especially comparing surgery and stereotactic body irradiation.

Solitary pulmonary nodule imaging approaches and the role of optical fibre-based technologies

Solitary pulmonary nodules (SPNs) are a clinical challenge, given there is no single clinical sign or radiological feature that definitively identifies a benign from a malignant SPN. The early detection of lung cancer has a huge impact on survival outcome. Consequently, there is great interest in the prompt diagnosis, and treatment of malignant SPNs. Current diagnostic pathways involve endobronchial/transthoracic tissue biopsies or radiological surveillance, which can be associated with suboptimal diagnostic yield, healthcare costs and patient anxiety. Cutting-edge technologies are needed to disrupt and improve, existing care pathways. Optical fibre-based techniques, which can be delivered via the working channel of a bronchoscope or via transthoracic needle, may deliver advanced diagnostic capabilities in patients with SPNs. Optical endomicroscopy, an autofluorescence-based imaging technique, demonstrates abnormal alveolar structure in SPNs in vivo Alternative optical fingerprinting approaches, such as time-resolved fluorescence spectroscopy and fluorescence-lifetime imaging microscopy, have shown promise in discriminating lung cancer from surrounding healthy tissue. Whilst fibre-based Raman spectroscopy has enabled real-time characterisation of SPNs in vivo Fibre-based technologies have the potential to enable in situ characterisation and real-time microscopic imaging of SPNs, which could aid immediate treatment decisions in patients with SPNs. This review discusses advances in current imaging modalities for evaluating SPNs, including computed tomography (CT) and positron emission tomography-CT. It explores the emergence of optical fibre-based technologies, and discusses their potential role in patients with SPNs and suspected lung cancer.

Lung-RADS Version 1.1: Challenges and a Look Ahead, From the AJR Special Series on Radiology Reporting and Data Systems

In 2014, the American College of Radiology (ACR) created Lung-RADS 1.0. The system was updated to Lung-RADS 1.1 in 2019, and further updates are anticipated as additional data become available. Lung-RADS provides a common lexicon and standardized nodule follow-up management paradigm for use when reporting lung cancer screening (LCS) low-dose CT (LDCT) chest examinations and serves as a quality assurance and outcome monitoring tool. The use of Lung-RADS is intended to improve LCS performance and lead to better patient outcomes. To date, the ACR's Lung Cancer Screening Registry is the only LCS registry approved by the Centers for Medicare & Medicaid Services and requires the use of Lung-RADS categories for reimbursement. Numerous challenges have emerged regarding the use of Lung-RADS in clinical practice, including the timing of return to LCS after planned follow-up diagnostic evaluation; potential substitution of interval diagnostic CT for future LDCT; role of volumetric analysis in assessing nodule size; assessment of nodule growth; assessment of cavitary, subpleural, and category 4X nodules; and variability in reporting of the S modifier. This article highlights the major updates between versions 1.0 and 1.1 of Lung-RADS, describes the system's ongoing challenges, and summarizes current evidence and recommendations.

Shades of Gray: Subsolid Nodule Considerations and Management

Subsolid nodules are common on chest CT imaging and may be either benign or malignant. Their varied features and broad differential diagnoses present management challenges. Although subsolid nodules often represent lung adenocarcinomas, other possibilities are common and influence management. Practice guidelines exist for subsolid nodule management for both incidentally and screening-detected nodules, incorporating patient and nodule characteristics. This review highlights the similarities and differences among these algorithms, with the intent of providing a resource for comparison and aid in choosing management options.

The Growth Rate of Subsolid Lung Adenocarcinoma Nodules at Chest CT

Background Confirming that subsolid adenocarcinomas show exponential growth is important because it would justify using volume doubling time to assess their growth. Purpose To test whether the growth of lung adenocarcinomas manifesting as subsolid nodules at chest CT is accurately represented by an exponential model. Materials and Methods Patients with lung adenocarcinomas manifesting as subsolid nodules surgically resected between January 2005 and May 2018, with three or more longitudinal CT examinations before resection, were retrospectively included. Overall volume (for all nodules) and solid component volume (for part-solid nodules) were measured over time. A linear mixed-effects model was used to identify the growth pattern (linear, exponential, quadratic, or power law) that best represented growth. The interactions between nodule growth and clinical, CT morphologic, and pathologic parameters were studied. Results Sixty-nine patients (mean age, 70 years ± 9 [standard deviation]; 48 women) with 74 lung adenocarcinomas were evaluated. Overall growth and solid component growth were better represented by an exponential model (adjusted R² = 0.89 and 0.95, respectively) than by a quadratic model (r² = 0.88 and 0.93, respectively), a linear model (r² = 0.87 and 0.92, respectively), or a power law model (r² = 0.82 and 0.93, respectively). Faster overall volume growth was associated with a history of lung cancer (P < .001), a baseline nodule volume less than 500 mm³ (P = .03), and histologic findings of invasive adenocarcinoma (P < .001). The median volume doubling time of noninvasive adenocarcinoma was significantly longer than that of invasive adenocarcinoma (939 days [interquartile range, 588-1563 days] vs 678 days [interquartile range, 392-916 days], respectively; P = .01). Conclusion The overall volume growth of adenocarcinomas manifesting as subsolid nodules at chest CT was best represented by an exponential model compared with the other tested models. This justifies the use of volume doubling time for the growth assessment of these nodules. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kuriyama and Yanagawa in this issue.

Assessing the Accuracy of a Deep Learning Method to Risk Stratify Indeterminate Pulmonary Nodules

Rationale: The management of indeterminate pulmonary nodules (IPNs) remains challenging, resulting in invasive procedures and delays in diagnosis and treatment. Strategies to decrease the rate of unnecessary invasive procedures and optimize surveillance regimens are needed.Objectives: To develop and validate a deep learning method to improve the management of IPNs.Methods: A Lung Cancer Prediction Convolutional Neural Network model was trained using computed tomography images of IPNs from the National Lung Screening Trial, internally validated, and externally tested on cohorts from two academic institutions.Measurements and Main Results: The areas under the receiver operating characteristic curve in the external validation cohorts were 83.5% (95% confidence interval [CI], 75.4-90.7%) and 91.9% (95% CI, 88.7-94.7%), compared with 78.1% (95% CI, 68.7-86.4%) and 81.9 (95% CI, 76.1-87.1%), respectively, for a commonly used clinical risk model for incidental nodules. Using 5% and 65% malignancy thresholds defining low- and high-risk categories, the overall net reclassifications in the validation cohorts for cancers and benign nodules compared with the Mayo model were 0.34 (Vanderbilt) and 0.30 (Oxford) as a rule-in test, and 0.33 (Vanderbilt) and 0.58 (Oxford) as a rule-out test. Compared with traditional risk prediction models, the Lung Cancer Prediction Convolutional Neural Network was associated with improved accuracy in predicting the likelihood of disease at each threshold of management and in our external validation cohorts.Conclusions: This study demonstrates that this deep learning algorithm can correctly reclassify IPNs into low- or high-risk categories in more than a third of cancers and benign nodules when compared with conventional risk models, potentially reducing the number of unnecessary invasive procedures and delays in diagnosis.

Overdiagnosis of lung cancer with low-dose computed tomography screening: meta-analysis of the randomised clinical trials

In low-dose computed tomography (LDCT) screening for lung cancer, all three main conditions for overdiagnosis in cancer screening are present: 1) a reservoir of slowly or nongrowing lung cancer exists; 2) LDCT is a high-resolution imaging technology with the potential to identify this reservoir; and 3) eligible screening participants have a high risk of dying from causes other than lung cancer. The degree of overdiagnosis in cancer screening is most validly estimated in high-quality randomised controlled trials (RCTs), with enough follow-up time after the end of screening to avoid lead-time bias and without contamination of the control group. Nine RCTs investigating LDCT screening were identified. Two RCTs were excluded because lung cancer incidence after the end of screening was not published. Two other RCTs using active comparators were also excluded. Therefore, five RCTs were included: two trials were at low risk of bias, two of some concern and one at high risk of bias. In a meta-analysis of the two low risk of bias RCTs including 8156 healthy current or former smokers, 49% of the screen-detected cancers were overdiagnosed. There is uncertainty about this substantial degree of overdiagnosis due to unexplained heterogeneity and low precision of the summed estimate across the two trials.

Key points

Nine randomised controlled trials (RCTs) on low-dose computed tomography screening were identified; five were included for meta-analysis but only two of those were at low risk of bias.In a meta-analysis of recent low risk of bias RCTs including 8156 healthy current or former smokers from developed countries, we found that 49% of the screen-detected cancers may be overdiagnosed.There is uncertainty about the degree of overdiagnosis in lung cancer screening due to unexplained heterogeneity and low precision of the point estimate.If only high-quality RCTs are included in the meta-analysis, the degree of overdiagnosis is substantial.

Educational aims

To appreciate that low-dose computed tomography screening for lung cancer meets all three main conditions for overdiagnosis in cancer screening: a reservoir of indolent cancers exists in the population; the screening test is able to "tap" this reservoir by detecting biologically indolent cancers as well as biologically important cancers; and the population being screened is characterised by a relatively high competing risk of death from other causesTo learn about biases that might affect the estimates of overdiagnosis in randomised controlled trials in cancer screening.

Current Controversies in Cardiothoracic Imaging: Low-dose Computerized Tomographic Overdiagnosis of Lung Cancer is Substantial; Its Consequences are Underappreciated-Point

Lung cancer seems an ideal screening candidate because of its frequency and lethality, its well-known risk factors, and because it can often be identified at a curable stage with noninvasive procedures. The lethality of clinically diagnosed lung cancers rendered the possibility of material overdiagnosis (OD) (by means of screening) implausible in the judgment of experienced clinicians. Increased experience with lung cancer screening trials, which showed an excess of cases in screened versus control cohorts, led to broader acceptance of its existence. The magnitude of OD and the appropriate methodology for its assessment are disputed. Overdiagnosed individuals experience substantial surgical mortality and their loss of pulmonary reserve leads, in many, to a material reduction in the duration and quality of life. To estimate the scale of computerized tomographic OD, taken as the excess of screen-identified cases versus unscreened controls, we pooled the long-term findings in the 3 reporting European trials comprising 10,675 subjects. There were 263 detected lung cancers in the low-dose, computerized tomographic-screened versus 153 in controls, a 42% excess.

Persisting new nodules in incidence rounds of the NELSON CT lung cancer screening study

BACKGROUND

The US guidelines recommend low-dose CT (LDCT) lung cancer screening for high-risk individuals. New solid nodules after baseline screening are common and have a high lung cancer probability. Currently, no evidence exists concerning the risk stratification of non-resolving new solid nodules at first LDCT screening after initial detection.

METHODS

In the Dutch-Belgian Randomized Lung Cancer Screening (NELSON) trial, 7295 participants underwent the second and 6922 participants the third screening round. We included participants with solid nodules that were registered as new or <15 mm³ (study detection limit) at previous screens and received additional screening after initial detection, thereby excluding high-risk nodules according to the NELSON management protocol (nodules ≥500 mm³).

RESULTS

Overall, 680 participants with 1020 low-risk and intermediate-risk new solid nodules were included. A total of 562 (55%) new solid nodules were resolving, leaving 356 (52%) participants with a non-resolving new solid nodule, of whom 25 (7%) were diagnosed with lung cancer. At first screening after initial detection, volume doubling time (VDT), volume, and VDT combined with a predefined ≥200 mm³ volume cut-off had high discrimination for lung cancer (VDT, area under the curve (AUC): 0.913; volume, AUC: 0.875; VDT and ≥200 mm³ combination, AUC: 0.939). Classifying a new solid nodule with either ≤590 days VDT or ≥200 mm³ volume positive provided 100% sensitivity, 84% specificity and 27% positive predictive value for lung cancer.

CONCLUSIONS

More than half of new low-risk and intermediate-risk solid nodules in LDCT lung cancer screening resolve. At follow-up, growth assessment potentially combined with a volume limit can be used for risk stratification.

TRIAL REGISTRATION NUMBER

ISRCTN63545820; pre-results.

Updated Fleischner Society Guidelines for Managing Incidental Pulmonary Nodules: Common Questions and Challenging Scenarios

The new guidelines for managing incidental pulmonary nodules published by the Fleischner Society in 2017 reflect an improved understanding of the risk factors and biologic features of lung cancer. Specific topics emphasized in the updated guidelines include a new threshold size for follow-up, the importance of the morphologic features of nodules, accurate nodule measurements, recognition of subsolid components, understanding interval growth or change in nodule morphology, and knowledge of patient risk factors. The updated guidelines enable greater personal flexibility in the decision-making process and encourage individualized management of pulmonary nodules. These factors may introduce new challenges for radiologists, who previously used solely nodule size to make management recommendations. The authors describe eight scenarios that illustrate the challenges potentially encountered when applying the new guidelines to pulmonary nodule management. ^©RSNA, 2018.

[Factors Influencing the Progression Trend of Early Lung Cancer and CT Findings]

背景与目的

不同类型的肺部结节具有不同的体积倍增时间（volume doubling time, VDT）。目前针对不同病理类型早期肺腺癌VDT的研究较少。本研究通过回顾性分析143例早期肺腺癌的影像资料，探讨早期肺腺癌的进展趋势及相关影响因素，为临床制订其随访策略提供参考。

方法

依据2015版世界卫生组织肺肿瘤分类标准和第8版肿瘤肿瘤-淋巴结-转移（tumor-node-metastasis, TNM）分期标准，对143例早期肺腺癌进行分类及分期。参考修正版Schwartz公式计算不同病理类型肺腺癌的VDT。

结果

143例早期肺腺癌中，有50例（34.97%）出现进展，多因素分析显示影响因素包括随访时间、结节大小、病理类型、结节类型和病理分期。附壁生长为主型肺腺癌（lepidic predominant adenocarcinoma, LPA）的VDT为（594±272）d，伴少量附壁生长成分浸润性腺癌的VDT为（520±285）d，完全浸润性腺癌的VDT为（371±183）d，3类进展性早期肺腺癌的VDT有统计学差异（P=0.044）。

结论

在早期肺腺癌中，约有35%的肿瘤处于进展阶段，是否含有附壁生长成分是影响肿瘤进展速度的重要因素。

In vivo growth of 60 non-screening detected lung cancers: a computed tomography study

Current pulmonary nodule management guidelines are based on nodule volume doubling time, which assumes exponential growth behaviour. However, this is a theory that has never been validated in vivo in the routine-care target population. This study evaluates growth patterns of untreated solid and subsolid lung cancers of various histologies in a non-screening setting.Growth behaviour of pathology-proven lung cancers from two academic centres that were imaged at least three times before diagnosis (n=60) was analysed using dedicated software. Random-intercept random-slope mixed-models analysis was applied to test which growth pattern most accurately described lung cancer growth. Individual growth curves were plotted per pathology subgroup and nodule type.We confirmed that growth in both subsolid and solid lung cancers is best explained by an exponential model. However, subsolid lesions generally progress slower than solid ones. Baseline lesion volume was not related to growth, indicating that smaller lesions do not grow slower compared to larger ones.By showing that lung cancer conforms to exponential growth we provide the first experimental basis in the routine-care setting for the assumption made in volume doubling time analysis.

Screening for early stage lung cancer and its correlation with lung nodule detection

Currently, the most effective way of reducing lung cancer mortality is early diagnosis of lung cancer. The National Lung Screening Trial has proved the efficacy of lung cancer screening using low-dose computed tomography to reduce lung cancer mortality. However, many questions remain surrounding lung cancer screening implementation, among which include how to select the optimal risk population, the personalized screening interval based different levels of risk, methods to improve diagnostic discrimination between malignant and benign disease in detected lung nodules, and the roles of biomolecular markers in stratifying risk and in guiding the management of indeterminate nodules. This review concentrates on the latest developments of lung cancer screening and provides an overview of the main unanswered questions on lung nodule detection.

Malignant solitary pulmonary nodules: assessment of mass growth rate and doubling time at follow-up CT

Background

The differentiation of benign and malignant solitary pulmonary nodules (SPNs), especially subsolid nodules, is still challenging because of the small size, slow growth, and atypical imaging characteristics of these nodules. We aimed to determine the significance of mass growth rate (MGR) and mass doubling time (MDT) at follow-up CT of malignant SPNs.

Methods

This retrospective study included 167 patients (169 SPNs, diameter 8-30 mm). Among the 169 SPNs, 114 malignant SPNs were classified into three types: pure ground-glass nodules (pGGNs), part-solid nodules (pSNs), and solid nodules (SNs). These patients were followed up for at least 3 months. Three-dimensional manual segmentation was performed for all these nodules, and the intra- and inter-observer variabilities of diameter, volume, and mass measurement were assessed. From initial and follow-up CT scans, growth rates of the diameter, volume, and mass of the SPNs were compared. MDT and volume doubling time (VDT) were calculated and were compared among groups.

Results

Mass measurements had the best inter-observer consistency and intra-observer repeatability; the coefficients of variation of the mass measurements were the smallest. The mean growth rates of the diameter, volume, and mass of pGGNs, pSNs, and SNs significantly differed at different time points (P<0.001). Mean MDTs and VDTs of pGGNs, pSNs, and SNs were 655 vs. 848 days, 462 vs. 598 days, and 230 vs. 267 days, respectively (P<0.05).

Conclusions

Mass measurements are an objective and accurate indicator in SPN assessment. During a 2-year follow-up, the mean growth rates of the diameter, volume, and mass of pGGNs, pSNs, and SNs differed at different time points, the greatest difference was observed in mean MGR. Mean MDT of malignant SPNs is less than the mean VDT.

Lung nodules: size still matters

The incidence of indeterminate pulmonary nodules has risen constantly over the past few years. Determination of lung nodule malignancy is pivotal, because the early diagnosis of lung cancer could lead to a definitive intervention. According to the current international guidelines, size and growth rate represent the main indicators to determine the nature of a pulmonary nodule. However, there are some limitations in evaluating and characterising nodules when only their dimensions are taken into account. There is no single method for measuring nodules, and intrinsic errors, which can determine variations in nodule measurement and in growth assessment, do exist when performing measurements either manually or with automated or semi-automated methods. When considering subsolid nodules the presence and size of a solid component is the major determinant of malignancy and nodule management, as reported in the latest guidelines. Nevertheless, other nodule morphological characteristics have been associated with an increased risk of malignancy. In addition, the clinical context should not be overlooked in determining the probability of malignancy. Predictive models have been proposed as a potential means to overcome the limitations of a sized-based assessment of the malignancy risk for indeterminate pulmonary nodules.

[Analysis of Growth Curve Type in Pulmonary Nodules with Different Characteristics]

背景与目的

计算机断层扫描（computed tomography, CT）随访评估肺内结节的生长特性是临床判断结节良恶性的常用策略。不同生物学行为的肺结节可能具有不同的生长速度和生长模式。本研究的目的是绘制不同类型肺结节的体积生长曲线，了解其生长方式，为判断结节性质并制定肺结节随访方案提供依据。

方法

应用三维分析软件对111例接受2次及以上CT检查的肺结节（实性结节54例、亚实性结节57例）的影像资料进行回顾性分析。35例恶性及5例良性结节经病理或组织学确认，其余71例经两年随访无显著生长，经专家会诊确认为肺癌低危结节。所有结节按密度及性质分组：实性良性/低危结节、实性恶性结节、亚实性良性/低危结节、亚实性恶性结节。以随访间隔时间（d）为X轴，以随访结节的三维体积（mm³）和三维体积对数为Y轴，绘制体积线性及指数性生长曲线，由研究者主观观察曲线的形态。应用卡方检验比较不同性质肺结节的生长曲线的差异。

结果

实性恶性结节中12例（66.7%）生长曲线快速上升，3例（16.7%）先平缓-后上升，2例（11.1%）缓慢上升，1例（5.56%）平直。亚实性恶性结节中8例（47.1%）呈快速上升型，4例（23.5%）缓慢上升，3例（17.6%）平直，2例（11.8%）为先下降-后上升型。实性良性/低危结节中5例（13.9%）呈下降型，17例（47.2%）平直，8例（21.6%）缓慢上升，6例（16.7%）呈波浪型。亚实性良性/低危结节中4例（10%）呈下降型，21例（52.5%）平直，9例（22.5%）缓慢上升，6例（15%）呈波浪型。良性/低危结节与恶性结节生长曲线分布存在显著性差异（χ²=42.4, P < 0.01）。

结论

肺癌生长曲线具有异质性，快速上升是恶性肺结节的特征性生长曲线，但部分可在一定时期内表现为平直、缓慢上升甚至下降。缓慢生长不能排除肺癌可能，尤其是亚实性结节。

Outcomes of unresected ground-glass nodules with cytology suspicious for adenocarcinoma

BACKGROUND

Five-year survival rates for resected stage I adenocarcinoma approach 100%. Given previous studies describing the prolonged indolent natural history of ground-glass lesions suspicious for early adenocarcinoma, our purpose in this study was to determine if outcomes were different among patients who were observed for radiographic and biopsy suspected early adenocarcinoma compared with those who were resected immediately.

METHODS

We identified 63 patients with no prior history of lung adenocarcinoma who had undergone computer tomography-guided fine-needle aspiration of ground-glass opacities with cytology concerning for new early adenocarcinoma between January 2002 and December 2011. We compared the clinical outcomes of patients who were resected after abnormal cytology results and those who opted for watchful waiting.

RESULTS

Sixteen patients elected to observe their ground-glass nodules despite having suspicious cytology results, whereas 47 opted for immediate resection. Of the 16 observed patients, six (37.5%) ultimately demonstrated growth or increase solid component of the ground-glass nodule. Five of these patients elected for definitive therapy by surgical resection or radiation. There were no occurrences of distant metastasis or lung cancer-associated deaths in the observed group. Of the 47 resected patients, two developed metastatic disease, five developed new cancers in remaining lung, and three developed progression in existing ground-glass nodules.

CONCLUSIONS

Ground-glass lesions that were observed after biopsy did not demonstrate any increased rates of metastasis or cancer-related deaths and delayed resection does not seem to have a negative effect on outcomes.

Screening for lung cancer

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the current data about low-dose computed tomography (LD-CT) lung cancer screening.

RECENT FINDINGS

The National Lung Screening Trial (NLST) was the first study that provided statistical evidence that LD-CT screening for lung cancer significantly reduces lung cancer mortality by 20%. Three statistically underpowered European trials could not confirm the positive effect of LD-CT screening on lung cancer mortality. Major obstacles in lung cancer screening are overdiagnosis and the large number of false-positive results. In the NLST, more than 24% of the screens were positive, most of which (96.4%) proved to be benign in nature. Optimized protocols for the workup of detected nodules may help to reduce the number of false-positive screens.

SUMMARY

Currently, the NLST is the only sufficiently powered trial to report a lower mortality rate with LD-CT screening. Long-term follow-up data are still anticipated on the European screening trials. Furthermore, data on the extent of the potential dangers of LD-CT screening, such as overdiagnosis, false-positive results, and the effect of cumulative radiation dose, have yet to be investigated thoroughly.

Diagnosis and management of pulmonary nodules

There are an increased number of pulmonary nodules discovered on CT scan images in part due to those performed for lung cancer screening. Risk stratification and patient involvement is critical in determining management ranging from interval imaging to invasive biopsy or surgery. A definitive diagnosis requires tissue biopsy. The choice of a particular biopsy technique depends on the risks/benefits of the procedure, the diagnostic yield and local expertise. This review will focus on the evaluation and management of pulmonary nodules based on the Fleischner Society and American College of Chest Physician guidelines. There have been recent changes to both societies' recommendations for incidental detection of solid and subsolid nodules, risk stratification, imaging, minimally invasive diagnostic techniques and definitive surgical options.

Impact of pretreatment tumor growth rate on outcome of early-stage lung cancer treated with stereotactic body radiation therapy

PURPOSE

To determine the influence of pretreatment tumor growth rate on outcomes in patients with early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT).

METHODS AND MATERIALS

A review was conducted on 160 patients with T1-T2N0M0 NSCLC treated with SBRT at single institution. The patient's demographic and clinical data, time interval (t) between diagnostic and planning computed tomography (CT), vital status, disease status, and cause of death were extracted from a prospectively kept database. Differences in gross tumor volume between diagnostic CT (GTV1) and planning CT (GTV2) were recorded, and growth rate was calculated by use of specific growth rate (SGR). Kaplan-Meier curves were constructed for overall survival (OS). Differences between groups were compared with a log-rank test. Multivariate analyses were performed by use of the Cox proportional hazard model with SGR and other relevant clinical factors. Cumulative incidence was calculated for local, regional, and distant failures by use of the competing risk approach and was compared with Gray's test.

RESULTS

The median time interval between diagnostic and planning CT was 82 days. The patients were divided into 2 groups, and the median SGR was used as a cut-off. The median survival times were 38.6 and 27.7 months for the low and high SGR groups, respectively (P=.03). Eastern Cooperative Oncology Group performance status (P=.01), sex (P=.04), SGR (P=.03), and GTV2 (P=.002) were predictive for OS in multivariable Cox regression analysis and, except sex, were similarly predictive for failure-free survival (FFS). The 3-year cumulative incidences of regional failure were 19.2% and 6.0% for the high and low SGR groups, respectively (P=.047).

CONCLUSION

High SGR was correlated with both poorer OS and FFS in patients with early-stage NSCLC treated with SBRT. If validated, this measurement may be useful in identifying patients most likely to benefit from adjuvant therapy after SBRT.

Volume and mass doubling times of persistent pulmonary subsolid nodules detected in patients without known malignancy

PURPOSE

To evaluate volume doubling time (VDT) and mass doubling time (MDT) of persistent pulmonary subsolid nodules (SSNs) followed-up with low-dose (LD) computed tomography (CT) in patients without a history of malignancy.

MATERIALS AND METHODS

This retrospective institutional review board-approved study, with waiver of patient informed consent, included 97 SSNs in 97 patients (45 men, 52 women; median age, 58 years; range, 37-87 years) in whom at least two LD CT scans were obtained, with 3-month or longer follow-up interval and median follow-up of 633 days. SSNs were categorized into pure ground-glass nodules (GGNs) (group A), part-solid GGNs with solid components of 5 mm or smaller (group B), and part-solid GGNs with solid components larger than 5 mm (group C). Three-dimensional manual segmentation for all SSNs was performed on initial and latest follow-up LD CT scans; subsequently, VDTs and MDTs were calculated and were compared among groups by using Kruskal-Wallis test, followed by the Dunn procedure with Bonferroni correction for volume-growing SSNs and mass-growing SSNs.

RESULTS

Volume growth was thus: 12 of 63 SSNs (19%), group A; nine of 23 SSNs (39%), group B; and eight of 11 SSNs (73%), group C. Median VDT was thus: 1832.3 days (range, 1230.7-4537.3 days), group A; 1228.5 days (range, 934.7-4617.7 days), group B; and 759.0 days (range, 376.4-941.5 days), group C. Mass growth was thus: 17 of 63 SSNs (27%), group A; 11 of 23 SSNs (48%), group B; and nine of 11 SSNs (82%), group C. Median MDT was 1556.1 days (range, 642.5-3564.5 days) for group A, 1199.9 days (range, 838.6-2578.7 days) for group B, and 627.7 days (range, 340.0-921.2 days) for group C. Median VDTs and MDTs of groups A and B were significantly longer than those of group C (P < .01).

CONCLUSION

Pure GGNs and part-solid GGNs with solid components of 5 mm or smaller show significantly longer VDTs and MDTs than do part-solid GGNs with solid components larger than 5 mm. Online supplemental material is available for this article.

Overdiagnosis in low-dose computed tomography screening for lung cancer

IMPORTANCE

Screening for lung cancer has the potential to reduce mortality, but in addition to detecting aggressive tumors, screening will also detect indolent tumors that otherwise may not cause clinical symptoms. These overdiagnosis cases represent an important potential harm of screening because they incur additional cost, anxiety, and morbidity associated with cancer treatment.

OBJECTIVE

To estimate overdiagnosis in the National Lung Screening Trial (NLST).

DESIGN, SETTING, AND PARTICIPANTS

We used data from the NLST, a randomized trial comparing screening using low-dose computed tomography (LDCT) vs chest radiography (CXR) among 53 452 persons at high risk for lung cancer observed for 6.4 years, to estimate the excess number of lung cancers in the LDCT arm of the NLST compared with the CXR arm.

MAIN OUTCOMES AND MEASURES

We calculated 2 measures of overdiagnosis: the probability that a lung cancer detected by screening with LDCT is an overdiagnosis (PS), defined as the excess lung cancers detected by LDCT divided by all lung cancers detected by screening in the LDCT arm; and the number of cases that were considered overdiagnosis relative to the number of persons needed to screen to prevent 1 death from lung cancer.

RESULTS

During follow-up, 1089 lung cancers were reported in the LDCT arm and 969 in the CXR arm of the NLST. The probability is 18.5% (95% CI, 5.4%-30.6%) that any lung cancer detected by screening with LDCT was an overdiagnosis, 22.5% (95% CI, 9.7%-34.3%) that a non-small cell lung cancer detected by LDCT was an overdiagnosis, and 78.9% (95% CI, 62.2%-93.5%) that a bronchioalveolar lung cancer detected by LDCT was an overdiagnosis. The number of cases of overdiagnosis found among the 320 participants who would need to be screened in the NLST to prevent 1 death from lung cancer was 1.38.

CONCLUSIONS AND RELEVANCE

More than 18% of all lung cancers detected by LDCT in the NLST seem to be indolent, and overdiagnosis should be considered when describing the risks of LDCT screening for lung cancer.

Features of resolving and nonresolving indeterminate pulmonary nodules at follow-up CT: the NELSON study

PURPOSE

To retrospectively identify features that allow prediction of the disappearance of solid, indeterminate, intraparenchymal nodules detected at baseline computed tomographic (CT) screening of individuals at high risk for lung cancer.

MATERIALS AND METHODS

The study was institutional review board approved. Participants gave informed consent. Participants with at least one noncalcified, solid, indeterminate, intraparenchymal nodule (volume range, 50-500 mm(3)) at baseline were included (964 nodules in 750 participants). According to protocol, indeterminate nodules were re-examined at a 3-month follow-up CT examination. Repeat screening was performed at years 2 and 4. A nodule was defined as resolving if it did not appear at a subsequent CT examination. Nodule resolution was regarded as spontaneous, not the effect of treatment. CT features of resolving and nonresolving (stable and malignant) nodules were compared by means of generalized estimating equations analysis.

RESULTS

At subsequent screening, 10.1% (97 of 964) of the nodules had disappeared, 77.3% (n = 75) of these at the 3-month follow-up CT and 94.8% (n = 92) at the second round of screening. Nonperipheral nodules were more likely to resolve than were peripheral nodules (odds ratio: 3.16; 95% confidence interval: 1.76, 5.70). Compared with smooth nodules, nodules with spiculated margins showed the highest probability of disappearance (odds ratio: 4.36; 95% confidence interval: 2.24, 8.49).

CONCLUSION

Approximately 10% of solid, intermediate-sized, intraparenchymal pulmonary nodules found at baseline screening for lung cancer resolved during follow-up, three-quarters of which had disappeared at the 3-month follow-up CT examination. Resolving pulmonary nodules share CT features with malignant nodules.

Characterization of lung cancer by amide proton transfer (APT) imaging: an in-vivo study in an orthotopic mouse model

Amide proton transfer (APT) imaging is one of the chemical exchange saturation transfer (CEST) imaging methods which images the exchange between protons of free tissue water and the amide groups (−NH) of endogenous mobile proteins and peptides. Previous work suggested the ability of APT imaging for characterization of the tumoral grade in the brain tumor. In this study, we tested the feasibility of in-vivo APT imaging of lung tumor and investigated whether the method could differentiate the tumoral types on orthotopic tumor xenografts from two malignant lung cancer cell lines. The results revealed that APT imaging is feasible to quantify lung tumors in the moving lung. The measured APT effect was higher in the tumor which exhibited more active proliferation than the other. The present study demonstrates that APT imaging has the potential to provide a characterization test to differentiate types or grade of lung cancer noninvasively, which may eventually reduce the need invasive needle biopsy or resection for lung cancer.

Nodule characterization: subsolid nodules

In this review, we focus on the radiologic, clinical, and pathologic aspects primarily of solitary subsolid pulmonary nodules. Particular emphasis will be placed on the pathologic classification and correlative computed tomography (CT) features of adenocarcinoma of the lung. The capabilities of fluorodeoxyglucose positron emission tomography-CT and histologic sampling techniques, including CT-guided biopsy, endoscopic-guided biopsy, and surgical resection, are discussed. Finally, recently proposed management guidelines by the Fleischner Society and the American College of Chest Physicians are reviewed.

Evaluation of individuals with pulmonary nodules: when is it lung cancer? Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines

OBJECTIVES

The objective of this article is to update previous evidence-based recommendations for evaluation and management of individuals with solid pulmonary nodules and to generate new recommendations for those with nonsolid nodules.

METHODS

We updated prior literature reviews, synthesized evidence, and formulated recommendations by using the methods described in the "Methodology for Development of Guidelines for Lung Cancer" in the American College of Chest Physicians Lung Cancer Guidelines, 3rd ed.

RESULTS

We formulated recommendations for evaluating solid pulmonary nodules that measure > 8 mm in diameter, solid nodules that measure ≤ 8 mm in diameter, and subsolid nodules. The recommendations stress the value of assessing the probability of malignancy, the utility of imaging tests, the need to weigh the benefits and harms of different management strategies (nonsurgical biopsy, surgical resection, and surveillance with chest CT imaging), and the importance of eliciting patient preferences.

CONCLUSIONS

Individuals with pulmonary nodules should be evaluated and managed by estimating the probability of malignancy, performing imaging tests to better characterize the lesions, evaluating the risks associated with various management alternatives, and eliciting their preferences for management.

Low-dose CT: technique, reading methods and image interpretation

The National Lung Cancer Screening Trial has recently demonstrated that screening of high-risk populations with the use of low-dose computed tomography (LDCT) reduces lung cancer mortality^[1]. Based on this encouraging result, the National Comprehensive Cancer Network guidelines recommended LDCT for selected patients at high risk of lung cancer^[2]. This suggests that an increasing number of CT screening examinations will be performed. The LDCT technique is relatively simple but some CT parameters are important and should be accurately defined in order to achieve good diagnostic quality and minimize the delivered dose. In addition, LDCT examinations are not as easy to read as they may initially appear; different approaches and tools are available for nodule detection and measurement. Moreover, the management of positive results can be a complex process and can differ significantly from routine clinical practice. Therefore this paper deals with the LDCT technique, reading methods and interpretation in lung cancer screening, particularly for those radiologists who have little experience of the technique.

Measurement methods and algorithms for the management of solid nodules

The increased detection of incidental small pulmonary nodules on multidetector computed tomography has driven attempts to refine the characterization and management of such nodules. A variety of methods have been developed to measure the size and biological activity of nodules to help define their nature, but these have limitations. Several clinical trials have assessed the efficacy of low-dose computed tomography screening for lung cancer and offer some insights into these limitations; however, they also provide evidence that refines existing nodule management strategies. This article reviews the size-based and functional measurement methods that can be used to predict the likelihood of malignancy in noncalcified solid pulmonary nodules and discusses their incorporation into existing algorithms for nodule management. The issue of multiple nodules and the optimum frequency and duration of follow-up are explored.

Current status of lung cancer screening

Recent results have demonstrated a major reduction in lung cancer mortality through computed tomography screening and no benefit from chest radiograph (CXR) screening. This presents a huge potential for benefit but also poses challenges regarding management of details to minimize harm. Many unresolved questions remain that must be addressed to implement computed tomography screening for lung cancer in a thoughtful and responsible way.

Recommendations for the management of subsolid pulmonary nodules detected at CT: a statement from the Fleischner Society

This report is to complement the original Fleischner Society recommendations for incidentally detected solid nodules by proposing a set of recommendations specifically aimed at subsolid nodules. The development of a standardized approach to the interpretation and management of subsolid nodules remains critically important given that peripheral adenocarcinomas represent the most common type of lung cancer, with evidence of increasing frequency. Following an initial consideration of appropriate terminology to describe subsolid nodules and a brief review of the new classification system for peripheral lung adenocarcinomas sponsored by the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS), six specific recommendations were made, three with regard to solitary subsolid nodules and three with regard to multiple subsolid nodules. Each recommendation is followed first by the rationales underlying the recommendation and then by specific pertinent remarks. Finally, issues for which future research is needed are discussed. The recommendations are the result of careful review of the literature now available regarding subsolid nodules. Given the complexity of these lesions, the current recommendations are more varied than the original Fleischner Society guidelines for solid nodules. It cannot be overemphasized that these guidelines must be interpreted in light of an individual's clinical history. Given the frequency with which subsolid nodules are encountered in daily clinical practice, and notwithstanding continuing controversy on many of these issues, it is anticipated that further refinements and modifications to these recommendations will be forthcoming as information continues to emerge from ongoing research.

Radiologic implications of the 2011 classification of adenocarcinoma of the lung

Now the leading subtype of lung cancer, adenocarcinoma received a new classification in 2011. For tumors categorized previously as bronchioloalveolar carcinoma (BAC), criteria and terminology had not been uniform, so the 2011 classification provided four new terms: (a) adenocarcinoma in situ (AIS), representing histopathologically a small (≤3-cm), noninvasive lepidic growth, which at computed tomography (CT) is usually nonsolid; (b) minimally invasive adenocarcinoma, representing histopathologically a small (≤3-cm) and predominantly lepidic growth that has 5-mm or smaller invasion, which at CT is mainly nonsolid but may have a central solid component of up to approximately 5 mm; (c) lepidic predominant nonmucinous adenocarcinoma, representing histopathologically invasive adenocarcinoma that shows predominantly lepidic nonmucinous growth, which at CT is usually part solid but may be nonsolid or occasionally have cystic components; and (d) invasive mucinous adenocarcinoma, histopathologically showing lepidic growth as its predominant component, which at CT varies widely from solid to mostly solid to part solid to nonsolid and may be single or multiple (when multifocal, it was formerly called multicentric BAC). In addition, new histopathologic subcategories of acinar, papillary, micropapillary, and solid predominant adenocarcinoma are now described, all as nonmucinous, predominantly invasive, may include a small lepidic component, and at CT are usually solid but may include a small nonsolid component. The micropapillary subtype has a poorer prognosis than the other subtypes. In addition, molecular genetic correlations for the subcategories of adenocarcinoma of the lung are now a topic of increasing interest. As the new classification enters common use, further descriptions of related correlations can be anticipated.