Return of the pulmonary nodule: the radiologist's key role in implementing the 2015 BTS guidelines on the investigation and management of pulmonary nodules

Artificial Intelligence in Lung Cancer Screening: The Future Is Now

Lung cancer has one of the worst morbidity and fatality rates of any malignant tumour. Most lung cancers are discovered in the middle and late stages of the disease, when treatment choices are limited, and patients' survival rate is low. The aim of lung cancer screening is the identification of lung malignancies in the early stage of the disease, when more options for effective treatments are available, to improve the patients' outcomes. The desire to improve the efficacy and efficiency of clinical care continues to drive multiple innovations into practice for better patient management, and in this context, artificial intelligence (AI) plays a key role. AI may have a role in each process of the lung cancer screening workflow. First, in the acquisition of low-dose computed tomography for screening programs, AI-based reconstruction allows a further dose reduction, while still maintaining an optimal image quality. AI can help the personalization of screening programs through risk stratification based on the collection and analysis of a huge amount of imaging and clinical data. A computer-aided detection (CAD) system provides automatic detection of potential lung nodules with high sensitivity, working as a concurrent or second reader and reducing the time needed for image interpretation. Once a nodule has been detected, it should be characterized as benign or malignant. Two AI-based approaches are available to perform this task: the first one is represented by automatic segmentation with a consequent assessment of the lesion size, volume, and densitometric features; the second consists of segmentation first, followed by radiomic features extraction to characterize the whole abnormalities providing the so-called "virtual biopsy". This narrative review aims to provide an overview of all possible AI applications in lung cancer screening.

Incidental chest findings on coronary CT angiography: a pictorial essay and management proposal

Many health systems have been using coronary CT angiography (CCTA) as a first-line examination for ischaemic heart disease patients in various countries. The rising number of CCTA examinations has led to a significant increase in the number of reported incidental extracardiac findings, mainly in the chest. Pulmonary nodules are the most common incidental findings on CCTA scans, as there is a substantial overlap of risk factors between the population seeking to exclude ischaemic heart disease and those at risk of developing lung cancer (i.e., advanced age and smoking habits). However, most incidental findings are clinically insignificant and actively pursuing them could be cost-prohibitive and submit the patient to unnecessary and potentially harmful examinations. Furthermore, there is little consensus regarding when to report or actively exclude these findings and how to manage them, that is, when to trigger an alert or to immediately refer the patient to a pulmonologist, a thoracic surgeon or a multidisciplinary team. This pictorial essay discusses the current literature on this topic and is illustrated with a review of CCTA scans. We also propose a checklist organised by organ and system, recommending actions to raise awareness of pulmonologists, thoracic surgeons, cardiologists and radiologists regarding the most significant and actionable incidental findings on CCTA scans.

The impact of cardiopulmonary hemodynamic factors in volumetry for pulmonary nodule management

BACKGROUND

The acceptance of coronary CT angiogram (CCTA) scans in the management of stable angina has led to an exponential increase in studies performed and reported incidental findings, including pulmonary nodules (PN). Using low-dose CT scans, volumetry tools are used in growth assessment and risk stratification of PN between 5 and 8 mm in diameter. Volumetry of PN could also benefit from the increased temporal resolution of CCTA scans, potentially expediting clinical decisions when an incidental PN is first detected on a CCTA scan, and allow for better resource management and planning in a Radiology department. This study aims to investigate how cardiopulmonary hemodynamic factors impact the volumetry of PN using CCTA scans. These factors include the cardiac phase, vascular distance from the main pulmonary artery (MPA) to the nodule, difference of the MPA diameter between systole and diastole, nodule location, and cardiomegaly presence.

MATERIALS AND METHODS

Two readers reviewed all CCTA scans performed from 2016 to 2019 in a tertiary hospital and detected PN measuring between 5 and 8 mm in diameter. Each observer measured each nodule using two different software packages and in systole and diastole. A multiple linear regression model was applied, and inter-observer and inter-software agreement were assessed using intraclass correlation.

RESULTS

A total of 195 nodules from 107 patients were included in this retrospective, cross-sectional and observational study. The regression model identified the vascular distance (p < 0.001), the difference of the MPA diameter between systole and diastole (p < 0.001), and the location within the lower or posterior thirds of the field of view (p < 0.001 each) as affecting the volume measurement. The cardiac phase was not significant in the model. There was a very high inter-observer agreement but no reasonable inter-software agreement between measurements.

CONCLUSIONS

PN volumetry using CCTA scans seems to be sensitive to cardiopulmonary hemodynamic changes independently of the cardiac phase. These might also be relevant to non-gated scans, such as during PN follow-up. The cardiopulmonary hemodynamic changes are a new limiting factor to PN volumetry. In addition, when a patient experiences an acute or deteriorating cardiopulmonary disease during PN follow-up, these hemodynamic changes could affect the PN growth estimation.

The diagnosis of pulmonary metastases on chest computed tomography in primary bone sarcoma and musculoskeletal soft tissue sarcoma

The lungs are the commonest site of metastasis for primary high-grade bone and soft tissue sarcoma, but current guidelines on the management of pulmonary nodules do not specifically cater for this group of patients. The current article reviews the literature from the past 20 years that has reported the CT features of pulmonary metastases in the setting of known primary bone and soft tissue sarcoma, with emphasis on osteosarcoma, chondrosarcoma, and trunk and extremity soft tissue sarcoma, the aim being to aid radiologists who report chest CT of musculoskeletal sarcoma patients in deciding which lesions should be considered metastatic, which lesions are indeterminate and require follow-up, and which lesions are of no concern.

Age-related treatment patterns for stage I NSCLC in three European countries

INTRODUCTION

Surgery is the preferred treatment for patients with early-stage non-small cell lung cancer (NSCLC) while stereotactic body radiation therapy (SBRT) may be applied in patients with major comorbidity or high age. We evaluated the association between age and treatment utilization for early-stage NSCLC in patients diagnosed in 2015-2016 in three European countries.

PATIENTS AND METHODS

Information was retrieved from population-based registries in England, Norway and the Netherlands. Treatment patterns and two-year overall survival rates for 105,124 patients with clinical stage I were analysed by age-group.

RESULTS

Surgical resection rates were higher in Norway (55%) and England (53%) than in the Netherlands (47%), and decreased with increasing age. SBRT use was highest in the Netherlands (41%), followed by Norway (29%) and England (12%). In the Netherlands, SBRT was the prevailing treatment in patients aged 70 years or older. In octogenarians, the proportion not receiving curative intent treatment was 53% in England, versus 35% in Norway and 22% in the Netherlands. Two-year survival rates were better for surgery than for SBRT and slightly better in Norway.

CONCLUSION

In patients aged 70 years or older, the proportion not receiving any curative treatment remains substantial, and differs significantly between countries. Measures to address these disparities are needed.

Improvement in Follow-up Imaging With a Patient Tracking System and Computerized Registry for Lung Nodule Management

PURPOSE

Despite established guidelines, radiologists' recommendations and timely follow-up of incidental lung nodules remain variable. To improve follow-up of nodules, a system using standardized language (tracker phrases) recommending time-based follow-up in chest CT reports, coupled with a computerized registry, was created.

MATERIALS AND METHODS

Data were obtained from the electronic health record and a facility-built electronic lung nodule registry. We evaluated two randomly selected patient cohorts with incidental nodules on chest CT reports: before intervention (September 2008 to March 2011) and after intervention (August 2011 to December 2016). Multivariable logistic regression was used to compare the cohorts for the main outcome of timely follow-up, defined as a subsequent report within 13 months of the initial report.

RESULTS

In all, 410 patients were included in the pretracker cohort versus 626 in the tracker cohort. Before system inception, 30% of CT reports lacked an explicit time-based recommendation for nodule follow-up. The proportion of patients with timely follow-up increased from 46% to 55%, and the proportion of those with no documented follow-up or follow-up beyond 24 months decreased from 48% to 31%. The likelihood of timely follow-up increased 41%, adjusted for high risk for lung cancer and age 65 years or older. After system inception, reports missing a tracker phrase for nodule recommendation averaged 6%, without significant interyear variation.

CONCLUSIONS

Standardized language added to CT reports combined with a computerized registry designed to identify and track patients with incidental lung nodules was associated with improved likelihood of follow-up imaging.

The utility of a convolutional neural network (CNN) model score for cancer risk in indeterminate small solid pulmonary nodules, compared to clinical practice according to British Thoracic Society guidelines

PURPOSE

To determine how implementation of an artificial intelligence nodule algorithm, the Lung Cancer Prediction Convolutional Neural Network (LCP-CNN), at the point of incidental nodule detection would have influenced further investigation and management using a series of threshold scores at both the benign and malignant end of the spectrum.

METHOD

An observational retrospective study was performed in the assessment of nodules between 5-15 mm (158 benign, 32 malignant) detected on CT scans, which were performed as part of routine practice. The LCP-CNN was applied to the baseline CT scan producing a percentage score, and subsequent imaging and management determined for each threshold group. We hypothesized that the 5% low risk threshold group requires only one follow-up, the 0.56% very low risk threshold group requires no follow-up and the 80% high risk threshold group warrants expedited intervention.

RESULTS

The 158 benign nodules had an LCP-CNN score between 0.1 and 70.8%, median 5.5% (IQR 1.4-18.0), whilst the 32 cancer nodules had an LCP-CNN score between 10.1 and 98.7%, median 59.0% (IQR 37.1-83.9). 24/61 CT scans in the 0.56-5% group (n = 37) and 21/21 CT scans <0.56% group (n = 13) could be obviated resulting in an overall reduction of 18.6% (45/242) CT scans in the benign cohort. In the 80% group (n = 10), expedited intervention of malignant nodules could result in a 3.6-month reduction in time delay in 5 cancer patients.

CONCLUSION

We show the potential of artificial intelligence to reduce the need for follow-up scans and intervention in low-scoring benign nodules, whilst potentially accelerating the investigation and treatment of high-scoring cancer nodules.

A review of staging chest CT in trunk and extremity soft tissue sarcoma

OBJECTIVES

To determine the incidence of pulmonary metastases on chest CT in trunk and extremity soft tissue sarcoma based on two size criteria, and to identify factors associated with metastases.

METHODS

Retrospective review of chest CT studies in patients with trunk and extremity soft tissue sarcoma over an 18-month period. Data collected included patient age/sex, tumour location, size and relationship to fascia. All chest CTs were reviewed for the presence of metastases which were diagnosed according to two size criteria: multiple nodules > 5 mm in size or multiple nodules > 10 mm in size. Follow-up CT studies were reviewed in cases initially considered indeterminate.

RESULTS

127 males and 73 females were included (mean age 57.1 years; range 10-90 years). 147 (73.5%) tumours were deep to the fascia and 53 (26.5%) superficial. Tumour size classified according to the 12 AJCC 2019 criteria was: T1 = 52, T2 = 76, T3 = 39, T4 = 33. Based on nodule size >5 mm, 73 (36.5%) patients had no metastases, 42 (21%) had metastases, while 85 (42.5%) studies were indeterminate. Based on nodule size >10 mm, 73 (36.5%) patients had no metastases, 28 (14%) had metastases, while 99 (49.5%) studies were indeterminate. Larger maximum dimension of the primary tumour was a risk factor for pulmonary metastases using both size criteria.

CONCLUSION

The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14-21%. 42.5-49.5% of chest CTs were indeterminate.

ADVANCES IN KNOWLEDGE

The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14-21%. Indeterminate pulmonary nodules are also very common.

The value of re-staging chest CT at first local recurrence of extremity and trunk soft tissue sarcoma

OBJECTIVE

To determine the prevalence of pulmonary metastases on re-staging chest CT at the time of first local recurrence (LR) of trunk or extremity soft tissue sarcoma (STS).

MATERIALS AND METHODS

Retrospective review of all patients diagnosed with recurrent STS between May 2007 and April 2018. Data collected included patient age and sex, site of primary STS, time to LR, recurrence site, initial tumour grade, recurrent tumour grade, findings of initial staging chest CT, and prevalence of pulmonary metastases on re-staging chest CT.

RESULTS

The study included 109 patients (males = 68, females = 41; mean age 56 years, range 9-92 years). The commonest tumour sub-types were myxofibrosarcoma (27.5%), undifferentiated pleomorphic/spindle cell sarcoma (20.2%), synovial sarcoma (10.1%), and malignant peripheral nerve sheath tumour (10.1%). Initial staging chest CT demonstrated pulmonary metastases in 1 of 77 (1.3%) patients for whom CT was available for review. The mean time to LR was 30.8 months (range 3-224 months). Pulmonary metastases were diagnosed on re-staging chest CT in 26 of 109 cases (23.9%), being commonest with grade 3 STS (36.1%). Pleomorphic sarcoma (85.7%) and undifferentiated spindle cell sarcoma (33.3%) were the 2 commonest tumour sub-types associated with pulmonary metastases at first LR.

CONCLUSION

Re-staging chest CT at the time of first LR of STS identified a prevalence of 23.9% pulmonary metastases, which supports the need for chest CT at the time of LR in line with the UK guidelines for the management of bone and soft tissue sarcoma.

KEY POINTS

• Pulmonary metastases were diagnosed in 1.3% of soft tissue sarcomas at presentation. • Pulmonary metastases were identified in ~ 24% of patients at first local recurrence of soft tissue sarcoma, most commonly with pleomorphic sarcoma and Trojani grade tumours. • No patient with a low-grade recurrence had pulmonary metastases.

Multi-observer concordance and accuracy of the British Thoracic Society scale and other visual assessment qualitative criteria for solid pulmonary nodule assessment using FDG PET-CT

AIM

To compare the interobserver reliability and diagnostic accuracy of the British Thoracic Society (BTS) scale and other visual assessment criteria in the context of 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET)-computed tomography (CT) evaluation of solid pulmonary nodules (SPNs).

MATERIALS AND METHODS

Fifty patients who underwent FDG PET-CT for assessment of a SPN were identified. Seven reporters with varied experience at four centres graded FDG uptake visually using the British Thoracic Society (BTS) four-point scale. Five reporters also scored SPNs according to three- and five-point visual assessment scales and using semi-quantitative assessment (maximum standardised uptake value [SUV_max]). Interobserver reliability was assessed with the intra-class correlation coefficient (ICC) and weighted Cohen's kappa (κ). Diagnostic performance was evaluated by receiver operator characteristic (ROC) analysis.

RESULTS

Good interobserver reliability was demonstrated with the BTS scale (ICC=0.78, 95% confidence interval [CI]: 0.69-0.85) and five-point scale (ICC=0.78, 95 CI 0.68-0.86), whilst the three-point scale demonstrated moderate reliability (ICC=0.70, 95% CI: 0.59-0.80). Almost perfect agreement was achieved between two consultants (κ=0.85), and substantial agreement between two other consultants (κ=0.78) using the BTS scale. ROC curves for the BTS and five-point scales demonstrated equivalent accuracy (BTS area under the ROC curve [AUC]=0.768; five-point AUC=0.768). SUV_max was no more accurate compared to the BTS scale (SUV_max AUC=0.794; BTS AUC=0.768, p=0.43).

CONCLUSIONS

The BTS scale can be applied reliably by reporters with varied levels of PET-CT reporting experience, across different centres and has a diagnostic performance that is not surpassed by alternative scales.

Implementation of a Standardized Template for Reporting of Incidental Pulmonary Nodules: Feasibility, Acceptability, and Outcomes

OBJECTIVE

Incidental pulmonary nodules (IPNs) are common. Up to 70% are not followed up according to current guidelines. Follow-up recommendations are based on the characteristics of the patient and the IPN. However, many IPNs are incompletely characterized in CT reports. Structured radiology reports have been shown to reduce missing information. We sought to improve IPN reporting by assessing the feasibility, acceptability, and effectiveness of a structured dictation template to increase the presence of six key nodule descriptors.

METHODS

We performed a mixed methods, pre- and postimplementation assessment. A template was developed with a multidisciplinary group based on Fleischner Society guidelines. A standardized checklist was used to determine the presence of documented descriptors pre- and postimplementation for sequential radiology reports of patients with an IPN present (n = 400 pre-implementation and n = 400 postimplementation) on a CT performed at the Minneapolis Veterans Affairs Health Care System. We conducted qualitative interviews with radiologists (n = 4) and members of the lung nodule tracking team (n = 2) to elicit their experiences of the template implementation process.

RESULTS

The proportion of radiology reports including all six elements increased from 12% to 47% (P < .001). Postimplementation, the template was used in 40% of interpretations involving lung nodules, 67% of follow-up scans, and 8% of initial identifications. Response to the template was overall positive.

DISCUSSION

Use of a dictation template seems to be effective in increasing compliance with full IPN documentation, streamlining the follow-up process. Low utilization rates of the template for initial nodule identification is a limitation, which may be combated through clearer communication and advances in technology.