Radiographic screening for cancer. Proposed paradigm for requisite research

A 20-year Follow-up of the International Early Lung Cancer Action Program (I-ELCAP)

Background The low-dose CT (≤3 mGy) screening report of 1000 Early Lung Cancer Action Program (ELCAP) participants in 1999 led to the International ELCAP (I-ELCAP) collaboration, which enrolled 31 567 participants in annual low-dose CT screening between 1992 and 2005. In 2006, I-ELCAP investigators reported the 10-year lung cancer-specific survival of 80% for 484 participants diagnosed with a first primary lung cancer through annual screening, with a high frequency of clinical stage I lung cancer (85%). Purpose To update the cure rate by determining the 20-year lung cancer-specific survival of participants diagnosed with first primary lung cancer through annual low-dose CT screening in the expanded I-ELCAP cohort. Materials and Methods For participants enrolled in the HIPAA-compliant prospective I-ELCAP cohort between 1992 and 2022 and observed until December 30, 2022, Kaplan-Meier survival analysis was used to determine the 10- and 20-year lung cancer-specific survival of participants diagnosed with first primary lung cancer through annual low-dose CT screening. Eligible participants were aged at least 40 years and had current or former cigarette use or had never smoked but had been exposed to secondhand tobacco smoke. Results Among 89 404 I-ELCAP participants, 1257 (1.4%) were diagnosed with a first primary lung cancer (684 male, 573 female; median age, 66 years; IQR, 61-72), with a median smoking history of 43.0 pack-years (IQR, 29.0-60.0). Median follow-up duration was 105 months (IQR, 41-182). The frequency of clinical stage I at pretreatment CT was 81% (1017 of 1257). The 10-year lung cancer-specific survival of 1257 participants was 81% (95% CI: 79, 84) and the 20-year lung cancer-specific survival was 81% (95% CI: 78, 83), and it was 95% (95% CI: 91, 98) for 181 participants with pathologic T1aN0M0 lung cancer. Conclusion The 10-year lung cancer-specific survival of 80% reported in 2006 for I-ELCAP participants enrolled in annual low-dose CT screening and diagnosed with a first primary lung cancer has persisted, as shown by the updated 20-year lung cancer-specific survival for the expanded I-ELCAP cohort. © RSNA, 2023 See also the editorials by Grenier and by Sequist and Olazagasti in this issue.

Pulmonary nodule radiological diagnostic algorithm in lung cancer screening

Publications of the final results of the two largest randomized lung cancer screening (LCS) trials in the United States and Europe confirmed the reduction in the mortality rate associated with the use of screening with low-dose computed tomography (LDCT). Results of these trials led to widespread acceptance of LCS in properly defined high-risk populations, and its implementation in the clinical practice. Many countries started preparation for national LCS and refreshed still open debate about lung nodule management. Detection of lung cancer in the early stage with a reduction of lung cancer mortality requires dedicated programs with optimized protocols, including a specified pulmonary nodule diagnostic algorithm. The screening protocol should be clear with a precise nodule diameter or volume threshold, based on which a positive screen result is defined. The application of risk-prediction models and the introduction of the semiautomated assessment of detected nodules improves screening accuracy and should be applied in LCS protocols as verified tools to aid radiological diagnosis. In this review, we have summarized recent data about the radiological protocols from the most important LCS programs and pulmonary diagnostic algorithms. These protocols should be taken into consideration in the ongoing and planned LCS programs.

Implementation of low-dose CT screening in two different health care systems: Mount Sinai Healthcare System and Phoenix VA Health Care System

Implementation of lung screening (LS) programs is challenging even among health care organizations that have the motivation, the resources, and more importantly, the goal of providing for life-saving early detection, diagnosis, and treatment of lung cancer. We provide a case study of LS implementation in different healthcare systems, at the Mount Sinai Healthcare System (MSHS) in New York City, and at the Phoenix Veterans Affairs Health Care System (PVAHCS) in Phoenix, Arizona. This will illustrate the commonalities and differences of the LS implementation process in two very different health care systems in very different parts of the United States. Underlying the successful implementation of these LS programs was the use of a comprehensive management system, the Early Lung Cancer Action Program (ELCAP) Management SystemTM. The collaboration between MSHS and PVAHCS over the past decade led to the ELCAP Management SystemTM being gifted by the Early Diagnosis and Treatment Research Foundation to the PVAHCS, to develop a "VA-ELCAP" version. While there remain challenges and opportunities to continue improving LS and its implementation, there is an increasing realization that most patients who are diagnosed with lung cancer as a result of annual LS can be cured, and that of all the possible risks associated with LS, the greater risk of all is for heavy cigarette smokers not to be screened. We identified 10 critical components in implementing a LS program. We provided the details of each of these components for the two healthcare systems. Most importantly, is that continual re-evaluation of the screening program is needed based on the ongoing quality assurance program and database of the actual screenings. At minimum, there should be an annual review and updating. As early diagnosis of lung cancer must be followed by optimal treatment to be effective, treatment advances for small, early lung cancers diagnosed as a result of screening also need to be assessed and incorporated into the entire screening and treatment program.

The Regimen of Computed Tomography Screening for Lung Cancer: Lessons Learned Over 25 Years From the International Early Lung Cancer Action Program

We learned many unanticipated and valuable lessons since we started planning our study of low-dose computed tomography (CT) screening for lung cancer in 1991. The publication of the baseline results of the Early Lung Cancer Action Project (ELCAP) in Lancet 1999 showed that CT screening could identify a high proportion of early, curable lung cancers. This stimulated large national screening studies to be quickly started. The ELCAP design, which provided evidence about screening in the context of a clinical program, was able to rapidly expand to a 12-institution study in New York State (NY-ELCAP) and to many international institutions (International-ELCAP), ultimately working with 82 institutions, all using the common I-ELCAP protocol. This expansion was possible because the investigators had developed the ELCAP Management System for screening, capturing data and CT images, and providing for quality assurance. This advanced registry and its rapid accumulation of data and images allowed continual assessment and updating of the regimen of screening as advances in knowledge and new technology emerged. For example, in the initial ELCAP study, introduction of helical CT scanners had allowed imaging of the entire lungs in a single breath, but the images were obtained in 10 mm increments resulting in about 30 images per person. Today, images are obtained in submillimeter slice thickness, resulting in around 700 images per person, which are viewed on high-resolution monitors. The regimen provides the imaging acquisition parameters, imaging interpretation, definition of positive result, and the recommendations for further workup, which now include identification of emphysema and coronary artery calcifications. Continual updating is critical to maximize the benefit of screening and to minimize potential harms. Insights were gained about the natural history of lung cancers, identification and management of nodule subtypes, increased understanding of nodule imaging and pathologic features, and measurement variability inherent in CT scanners. The registry also provides the foundation for assessment of new statistical techniques, including artificial intelligence, and integration of effective genomic and blood-based biomarkers, as they are developed.

Separation of bones from soft tissue in chest radiographs: Anatomy-specific orientation-frequency-specific deep neural network convolution

PURPOSE

Lung nodules that are missed by radiologists as well as by computer-aided detection (CAD) systems mostly overlap with ribs and clavicles. Removing the bony structures would result in better visualization of undetectable lesions. Our purpose in this study was to develop a virtual dual-energy imaging system to separate ribs and clavicles from soft tissue in chest radiographs.

METHODS

We developed a mixture of anatomy-specific, orientation-frequency-specific (ASOFS) deep neural network convolution (NNC) experts. Anatomy-specific (AS) NNC was designed to separate the bony structures from soft tissue in different lung segments. While an AS design was proposed previously under our massive-training artificial neural networks (MTANN) framework, in this work, we newly mathematically defined an AS experts model as well as its learning and inference strategies in a probabilistic deep-learning framework. In addition, in combination with our AS experts design, we newly proposed the orientation-frequency-specific (OFS) NNC models to decompose bone and soft-tissue structures into specific orientation-frequency components of different scales using a multi-resolution decomposition technique. We trained multiple NNC models, each of which is an expert for a specific orientation-frequency component in a particular anatomic segment. Perfect reconstruction discrete wavelet transform was used for OFS decomposition/reconstruction, while we introduced a soft-gating layer to merge the predictions of AS NNC experts. To train our model, we used the bone images obtained from a dual-energy system as the target (or teaching) images while the standard chest radiographs were used as the input to our model. The training, validation, and test were performed in a nested two-fold cross-validation manner.

RESULTS

We used a database of 118 chest radiographs with pulmonary nodules to evaluate our NNC scheme. In order to evaluate our scheme, we performed quantitative and qualitative evaluation of the predicted bone and soft-tissue images from our model as well as the ones of a state-of-the-art technique where the "gold-standard" dual-energy bone and soft-tissue images were used as the reference images. Both quantitative and qualitative evaluations demonstrated that our ASOFS NNC was superior to the state-of-the-art bone-suppression technique. Particularly, our scheme was better able to maintain the conspicuity of nodules and lung vessels, comparing to the reference technique, while it separated ribs and clavicles from soft tissue. Comparing to a state-of-the-art bone suppression technique, our bone images had substantially higher (t-test; P < 0.01) similarity, in terms of structural similarity index (SSIM) and peak signal-to-noise ratio (PSNR), to the "gold-standard" dual-energy bone images.

CONCLUSIONS

Our deep ASOFS NNC scheme can decompose chest radiographs into their bone and soft-tissue images accurately, offering the improved conspicuity of lung nodules and vessels, and therefore would be useful for radiologists as well as CAD systems in detecting lung nodules in chest radiographs.

Clarification of the resection line non-intubated segmentectomy using indocyanine green

A reflection on the measure of fluorescence specificity of indocyanine green (ICG) in non-intubated pulmonary segmentectomy.

Development of Protocol for Korean Lung Cancer Screening Project (K-LUCAS) to Evaluate Effectiveness and Feasibility to Implement National Cancer Screening Program

Purpose

To reduce lung cancer mortality, lung cancer screening was recommended using low-dose computed tomography (LDCT) to high-risk population. A protocol for multicenter lung cancer screening pilot project was developed to evaluate the effectiveness and feasibility of lung cancer screening to implement National Cancer Screening Program in Korea.

Materials and Methods

Multidisciplinary expert committee was comprised to develop a standardized protocol for Korean Lung Cancer Screening Project (K-LUCAS). K-LUCAS is a population-based single arm trial that targets high-risk population aged 55-74 years with at least 30 pack-year smoking history. LDCT results are reported by Lung-RADS suggested by American Radiology Society. Network-based system using computer-aided detection program is prepared to assist reducing diagnostic errors. Smoking cessation counselling is provided to all currently smoking participants. A small pilot test was conducted to check the feasibility and compliance of the protocols for K-LUCAS.

Results

In pilot test, 256 were participated. The average age of participants was 63.2 years and only three participants (1.2%) were female. The participants had a smoking history of 40.5 pack-year on average and 53.9% were current smokers. Among them, 86.3% had willing to participate in lung cancer screening again. The average willingness to quit smoking among current smokers was 12.7% higher than before screening. In Lung-RADS reports, 10 (3.9%) were grade 3 and nine (3.5%) were grade 4. One participant was diagnosed as lung cancer.

Conclusion

The protocol developed by this study is assessed to be feasible to perform K-LUCAS in multicenter nationwide scale.

CT Screening for Lung Cancer: Part-Solid Nodules in Baseline and Annual Repeat Rounds

OBJECTIVE

The purpose of this study was to assess the frequencies of identifying participants with part-solid nodules, of diagnostic pursuit, of diagnoses of lung cancer, and long-term lung cancer survival in baseline and annual repeat rounds of CT screening in the International Early Lung Cancer Action Project.

MATERIALS AND METHODS

Screenings were performed under a common protocol. Participants with solid, nonsolid, and part-solid nodules and the diagnoses of lung cancer were documented.

RESULTS

Part-solid nodules were identified in 2892 of 57,496 (5.0%) baseline screening studies; 567 (19.6%) of these nodules resolved or decreased in size. Diagnostic pursuit led to the diagnosis of adenocarcinoma in 79 cases, all clinical stage I. At resection, one nodule (12-mm solid component) had a single N2 metastasis. A new part-solid nodule was identified in 541 of 64,677 (0.8%) annual repeat screenings; 377 (69.7%) of these nodules resolved or decreased in size. In eight cases among the 541, the diagnosis of adenocarcinoma manifesting as a part solid nodule was made; on retrospective review the nodule originally had been a nonsolid nodule. In another 20 cases, the cancer originally had manifested as a nonsolid nodule but had progressed to become part-solid at annual repeat screening before any diagnosis was pursued. These 28 annual repeat cases of lung cancer were all pathologic stage IA. Of the 107 cases of lung cancer (79 baseline cases and 28 annual repeat cases), 106 were surgically resected, and one baseline case was followed up with imaging for 4 years. The lung cancer survival rate was 100% with a median follow-up period from diagnosis of 89 months (interquartile range, 52-134 months).

CONCLUSION

Lung cancers manifesting as part-solid nodules at repeat screening studies all started as nonsolid nodules. Among 107 cases of adenocarcinoma manifesting as a part-solid nodule, a single lymph node metastasis was found in a single case (solid component, 12 mm).

The importance of the regimen of screening in maximizing the benefit and minimizing the harms

BACKGROUND

In CT screening for lung cancer, the regimen of screening is critical in diagnosing lung cancer early while limiting unnecessary tests and invasive procedures. The International Early Lung Cancer Action Program (I-ELCAP) has developed a regimen based on evidence collected in the I-ELCAP cohort of more than 70,000 participants.

METHODS

Important in the development of the regimen is the recognition of the profound difference between the first, baseline round of screening and all subsequent rounds of repeat screening. For each person undergoing screening, the baseline round happens only once while repeat rounds will be performed annually for many years. This difference needs to be clearly recognized as it is these annual rounds which allow for identification of small, early, yet aggressive, lung cancers which have high cure rates despite their aggressiveness. The importance of nodule consistency and size are key factors in the regimen. The regimen needs to be continuously updated by incorporating advances in technology and knowledge.

RESULTS

The use of the I-ELCAP regimen reduces the workup of participants in the screening program to less than 10% in the baseline round and less than 6% in the annual repeat rounds. By use of this regimen, estimated cure rate of lung cancers diagnosed under screening is 80% or higher in both baseline and annual repeat rounds.

CONCLUSIONS

The I-ELCAP collaboration provides a new paradigm that answers the 2002 NCI call for multiple approaches to address relevant questions about screening and the Institute of Medicine (IOM) Roundtable on Evidence-based Medicine from the National Academy of Science's call for a "new clinical research paradigm that takes better advantage of data generated in the course of healthcare delivery would speed and improve the development of evidence for real-world decision making".

Separation of bones from chest radiographs by means of anatomically specific multiple massive-training ANNs combined with total variation minimization smoothing

Most lung nodules that are missed by radiologists as well as computer-aided detection (CADe) schemes overlap with ribs or clavicles in chest radiographs (CXRs). The purpose of this study was to separate bony structures such as ribs and clavicles from soft tissue in CXRs. To achieve this, we developed anatomically specific multiple massive-training artificial neural networks (MTANNs) combined with total variation (TV) minimization smoothing and a histogram-matching-based consistency improvement method. The anatomically specific multiple MTANNs were designed to separate bones from soft tissue in different anatomic segments of the lungs. Each of the MTANNs was trained with the corresponding anatomic segment in the teaching bone images. The output segmental images from the multiple MTANNs were merged to produce an entire bone image. TV minimization smoothing was applied to the bone image for reduction of noise while preserving edges. This bone image was then subtracted from the original CXR to produce a soft-tissue image where bones were separated out. This new method was compared with conventional MTANNs with a database of 110 CXRs with nodules. Our new anatomically specific MTANNs separated rib edges, ribs close to the lung wall, and the clavicles from soft tissue in CXRs to a substantially higher level than did the conventional MTANNs, while the conspicuity of lung nodules and vessels was maintained. Thus, our technique for bone-soft-tissue separation by means of our new MTANNs would be potentially useful for radiologists as well as CADe schemes in detection of lung nodules on CXRs.

Image analysis of small pulmonary nodules identified by computed tomography

Detection of small pulmonary nodules has markedly increased as computed tomography (CT) technology has advanced and interpretation evolved from viewing small CT images on film to magnified images on large, high-resolution computer monitors. Despite these advances, determining the etiology of a lung nodule short of major surgery remains problematic. Initial nodule size is a major criterion in evaluating the risk for malignancy, and the majority of CT detected nodules are <10 mm in diameter. Also, the likelihood that the nodule is a lung cancer increases with increasing age and smoking history, and such clinical information needs to be integrated into algorithms that guide the workup of such nodules. Baseline and annual repeat screening results are also very helpful in developing and assessing the usefulness of such algorithms. Based on CT morphology, subtypes of nodules have been identified; today nodules are routinely classified as being solid, part-solid, or nonsolid. It has been shown that part-solid nodules have a higher frequency of being malignant than solid or nonsolid ones. Other nodule characteristics such as spiculation are useful, although granulomas and fibrosis also have such features, so these characteristics have not been as useful as nodule-growth assessment. Depending on the aggressiveness of the lung cancer and the size of the nodule when it is initially seen, a follow-up CT scan 1-3 months after the first CT scan can identify those nodules with growth at a malignant rate. Software has been developed by all CT scanner manufacturers for such growth assessment, but the inherent variability of such assessments needs further development. Nodule-growth assessment based on 2-dimensional approaches is limited; therefore, software has been developed for the 3-dimensional assessment of growth. Different approaches for such growth assessment have been developed, either using automated computer segmentation techniques or hybrid methods that allow the radiologist to adjust such segmentation. There are, however, inherent reasons for variability in such measurements that need to be carefully considered, and this, together with continued technologic advances and integration of the relevant clinical information, will allow for individualization of the algorithms for the workup of small pulmonary nodules.

CT screening for lung cancer: update 2007

Screening is the pursuit of the early diagnosis of cancer before symptoms occur. The purpose of early diagnosis is to provide early treatment, which potentially prevents death from the cancer. The usefulness of screening depends on how early the cancer can be diagnosed and how many deaths can be prevented by early treatment as compared with later symptom-prompted diagnosis and treatment. The goal of the Early Lung Cancer Action Project investigators was to develop an efficient methodology that would provide an ever-accumulating, continually updated body of evidence for evaluation of emerging new technologies for screening for cancer. This methodology recognizes that screening is a sequential process that starts with the pursuit of the early diagnosis of cancer followed by early treatment. It also recognizes that diagnostic research is fundamentally different from treatment research. To fully understand the current discussions on the evidence for lung cancer screening, key definitions are provided, including the differentiation between the first, baseline round of screening and all subsequent rounds of repeat screening and baseline and repeat cancers and their distribution by cell type. These definitions are critical in analyzing the results of various screening reports as they are not used by all. To provide optimal screening, a regimen for the diagnostic workup must be specified starting with the definition of the initial test, its positive result, and the workup for a positive result leading to a diagnosis of cancer. Assessment of diagnostic performance does not require a control group, but does require confirmation of the diagnosis. For assessment of the effectiveness of early treatment, a comparison group is needed. The comparison group may be formed by randomly assigning people with screen-diagnosed lung cancer to immediate or delayed treatment, as has been done for prostate cancer. This provides a direct assessment of any potential overdiagnosis of the cancer resulting from screening. Alternatively, a quasiexperimental control group can be used consisting of participants diagnosed with the cancer who have refused or delayed their treatment even though they are candidates for it.

CT Screening for lung cancer: diagnoses resulting from the New York Early Lung Cancer Action Project

PURPOSE

To evaluate prospectively the diagnostic performance of the New York Early Lung Cancer Action Project (NY-ELCAP) regimen in the diagnosis of early lung cancer at baseline and annual repeat computed tomographic (CT) screenings.

MATERIALS AND METHODS

Informed consent and institutional review board approval were obtained for this HIPAA-compliant study of baseline and annual repeat low-dose CT screening performed with a common regimen in asymptomatic individuals at 12 institutions in New York State. All 6295 participants were aged 60 years or older, had smoked for at least 10 pack-years, had no prior cancer, had not undergone chest CT in the previous 3 years, and were medically fit to undergo thoracic surgery. Median age was 66 years, and median smoking history was 40 pack-years. The proportion (and 95% exact confidence intervals [CIs]) of subjects with a positive result, as determined by using nodule size; the diagnoses of lung cancer resulting from subsequent work-up; and the distribution by cancer stage and cell type were determined. When relevant, 95% CIs for the proportions were calculated.

RESULTS

Initial CT imaging led to recommendations for further work-up in 14.4% (95% CI: 13.5%, 15.3%) of the 6295 baseline screenings and 6.0% (95% CI: 5.1%, 6.6%) of the 6014 annual repeat screenings. Of 101 patients in whom the diagnosis of lung cancer resulted from baseline screening and three in whom a diagnosis of lung cancer was prompted by symptoms prior to the first scheduled repeat screening, 95 (91.3%) had no clinical evidence of metastases. Of the 20 patients in whom the diagnosis of lung cancer resulted from annual repeat screening, 17 (85%) showed no evidence of metastases. Of the 134 recommended biopsies, 125 (93.3%) resulted in diagnosis of lung cancer or another malignancy, while none of the 24 biopsies performed outside of the recommendation of the regimen resulted in diagnosis of lung cancer.

CONCLUSION

The NY-ELCAP regimen of screening revealed that annual CT screening for lung cancer resulted in identification of a high proportion of patients with early-stage disease.

Evaluation of lung MDCT nodule annotation across radiologists and methods

RATIONALE AND OBJECTIVES

Integral to the mission of the National Institutes of Health-sponsored Lung Imaging Database Consortium is the accurate definition of the spatial location of pulmonary nodules. Because the majority of small lung nodules are not resected, a reference standard from histopathology is generally unavailable. Thus assessing the source of variability in defining the spatial location of lung nodules by expert radiologists using different software tools as an alternative form of truth is necessary.

MATERIALS AND METHODS

The relative differences in performance of six radiologists each applying three annotation methods to the task of defining the spatial extent of 23 different lung nodules were evaluated. The variability of radiologists' spatial definitions for a nodule was measured using both volumes and probability maps (p-map). Results were analyzed using a linear mixed-effects model that included nested random effects.

RESULTS

Across the combination of all nodules, volume and p-map model parameters were found to be significant at P < .05 for all methods, all radiologists, and all second-order interactions except one. The radiologist and methods variables accounted for 15% and 3.5% of the total p-map variance, respectively, and 40.4% and 31.1% of the total volume variance, respectively.

CONCLUSION

Radiologists represent the major source of variance as compared with drawing tools independent of drawing metric used. Although the random noise component is larger for the p-map analysis than for volume estimation, the p-map analysis appears to have more power to detect differences in radiologist-method combinations. The standard deviation of the volume measurement task appears to be proportional to nodule volume.

[Historic landmarks in the study of lung cancer]

This study reviews the milestones which have been reached in the study of lung cancer, from its first early descriptions up until the end of the twentieth century. The study accompanies the birth of this new clinical entity, underlining the difficulties inherent in its diagnosis, its ever-growing increase and traces the growth of its aetiological factors, placing particular emphasis on smoking. In tandem with this, the study delves into the clinical aspects, along with new discoveries in imaging techniques and endoscopic and bioscopic techniques. It also looks at the histopathological classifications of bronchopulmonary tumours and the various staging systems which have been used over the course of time as well as the importance of mapping the disease and the different treatment weapons which have successively become available in the fight against it. The study also takes a look at the scales used in evaluating patients' physiological condition, the criteria used in evaluating response to oncostatic treatment and the role some international and national scientific societies and medical associations have played in adding to the increasing medical knowledge of lung cancer. The study clearly shows to whom we are indebted for each advance. This is a fascinating sweep of history - as is the story of all medical progress - and one we feel is important to understand, in order for us to see more clearly where we are now.

Image-processing technique for suppressing ribs in chest radiographs by means of massive training artificial neural network (MTANN)

When lung nodules overlap with ribs or clavicles in chest radiographs, it can be difficult for radiologists as well as computer-aided diagnostic (CAD) schemes to detect these nodules. In this paper, we developed an image-processing technique for suppressing the contrast of ribs and clavicles in chest radiographs by means of a multiresolution massive training artificial neural network (MTANN). An MTANN is a highly nonlinear filter that can be trained by use of input chest radiographs and the corresponding "teaching" images. We employed "bone" images obtained by use of a dual-energy subtraction technique as the teaching images. For effective suppression of ribs having various spatial frequencies, we developed a multiresolution MTANN consisting of multiresolution decomposition/composition techniques and three MTANNs for three different-resolution images. After training with input chest radiographs and the corresponding dual-energy bone images, the multiresolution MTANN was able to provide "bone-image-like" images which were similar to the teaching bone images. By subtracting the bone-image-like images from the corresponding chest radiographs, we were able to produce "soft-tissue-image-like" images where ribs and clavicles were substantially suppressed. We used a validation test database consisting of 118 chest radiographs with pulmonary nodules and an independent test database consisting of 136 digitized screen-film chest radiographs with 136 solitary pulmonary nodules collected from 14 medical institutions in this study. When our technique was applied to nontraining chest radiographs, ribs and clavicles in the chest radiographs were suppressed substantially, while the visibility of nodules and lung vessels was maintained. Thus, our image-processing technique for rib suppression by means of a multiresolution MTANN would be potentially useful for radiologists as well as for CAD schemes in detection of lung nodules on chest radiographs.

CT screening for lung cancer: update 2005

Currently available results on CT screening for lung cancer show that (1) the work-up on baseline screening can be confined to less than 15% of the individuals and to less than 6% on annual repeat screening, (2) almost all cases are detected by screening with very few diagnoses made between screening on the prompting of symptoms, and (3) over 80% of all the diagnoses are of stage I. This diagnostic performance results from following the I-ELCAP regimen of screening which defines a positive result of the initial CT in the regimen as well as the work-up leading to a diagnosis of lung cancer. The diagnostic performance raises prognostic questions as to the genuineness and curability of these screen-diagnosed lung cancers. All diagnoses of malignancy were confirmed by an expert pathology review and found to represent genuine lung cancer as defined by the 2004 World Health Organization pathologic criteria. Estimates based on growth rates suggest that about 90% of the baseline-diagnosed stage I cancers are genuine cancers, as are essentially all of those diagnosed on annual repeat screening. Preliminary results of the curability of genuine screen-diagnosed stage I lung cancers indicate a high curability rate of more than 90%. This suggests that more than a high proportion of deaths from lung cancer can be prevented by CT screening followed by early resection. Using these results, the benefit of a single round of CT screening can be determined for an individual based on the age and smoking history.

An Update of CT Screening for Lung Cancer

Currently available results on CT screening for lung cancer show that 1) the work-up on baseline screening can be confined to less than 15% of the individuals and to less than 6% on annual repeat screening, 2) almost all cases are detected by screening with very few diagnoses made between screening on the prompting of symptoms, and 3) over 80% of all the diagnoses are of Stage I. This diagnostic performance results from following the I-ELCAP regimen of screening which defines a positive result of the initial CT in the regimen as well as the work-up leading to a diagnosis of lung cancer. The diagnostic performance raises prognostic questions as to the genuineness and curability of these screen-diagnosed lung cancers. All diagnoses of malignancy were confirmed by an expert pathology review and found to represent genuine lung cancer as defined by the 2004 World Health Organization pathologic criteria. Estimates based on growth rates suggest that about 90% of the baseline-diagnosed Stage I cancers are genuine cancers as are essentially all of those diagnosed on annual repeat screening. Preliminary results of the curability of genuine screen-diagnosed Stage I lung cancers indicate a high curability rate of more than 90%. This suggests that more than a high proportion of deaths from lung cancer can be prevented by CT screening followed by early resection.

CT Screening for Lung Cancer: Past and Ongoing Studies

It has been widely recognized that the oft-quoted randomized clinical trials (RCTs) of lung cancer screening by chest radiography--studies that were interpreted as showing no benefit--were seriously flawed. We begin by describing the shortcomings of these trials and presenting an analysis of the problems typically encountered in performing RCTs in this area. Screening for lung cancer using computed tomography (CT) has shown that CT offers great superiority over chest radiography in diagnosing small lung cancers in the three studies that performed both CT and chest radiography on all patients. The Early Lung Cancer Action Project (ELCAP), showed that false-positive results can be kept reasonably low and are much less common on repeat screening, and that CT screening can be managed with no notable excess of percutaneous or surgical biopsies when following a well-defined regimen of screening. This regimen details the parameters of the initial CT, the definition of a positive result, and the subsequent work-up of positive results. Following the updated International (I)-ELCAP protocol, it has been further found that (1) the frequency of positive results is low: 15% for the baseline cycle of screening and 6% for the subsequent cycles. (2) The frequency of screen-diagnoses as compared with all diagnoses is 97% or higher. (3) The relative frequency of presurgical Stage I is well over 80%; the median diameter of the screen-diagnosed cases on repeat screening is 8 mm (versus 15 mm at baseline screening). (4) A high percentage of the screen-diagnosed cases were genuine cancers which led to death if not treated. (5) The estimated 8-year cure rate for resected baseline screen-diagnosed lung cancers without evidence of lymph node metastases is 95% and for resected annual repeat cancers is 98%. (6) CT screening appears to be highly cost-effective. These preliminary results of CT screening suggests that the cure rate of screen-diagnosed lung cancer, using the I-ELCAP regimen of screening, may be over 70% as compared with that of usual care of 10% and that of chest radiographic screening of 20%.

Lung Cancer Screening: Simulations of Effects of Imperfect Detection on Temporal Dynamics

PURPOSE

To use a mathematic model to demonstrate effects of imperfect detection on temporal dynamics of radiologic lung cancer screening.

MATERIALS AND METHODS

Monte Carlo simulations of lung cancer screening programs were performed in subjects at high risk for developing cancer. The effects of detection probabilities, symptomatic presentation of tumors, tumor volume doubling time, and time between screenings were examined. Computed tomography (CT) and chest radiography models were used.

RESULTS

For imperfect detection probabilities, the percentage of subjects with cancers detected with repeated screenings decreased to a steady-state value. The transition period was the period during which screenings were performed and detection rates decreased. At steady-state repeat screening, the proportion of subjects with cancers diagnosed at screening or by means of symptomatic presentation was determined by the annual probability of developing cancer and not by the sensitivity of the screening modality. The sensitivity of the screening technique did affect detected cancer size, number of interval cancers, and total number of cancers observed. CT was used to detect more total cancers over the course of the screening program and cancers with a smaller average size; moreover, fewer interval cancers were observed with CT screening than with chest radiography screening.

CONCLUSION

Lung cancer screening with imperfect detection has a transition period between baseline screening and steady-state behavior of annual screenings. Advantages of CT screening include a decrease in the average cancer size at detection, a decrease in the number of observed interval cancers, and an increase in the total number of cancers observed. Steady-state behavior indicates that long-term trials of screening may not be necessary.

State-of-the-art screening for lung cancer: (part 2): CT scanning

There have been dramatic improvements in technology in the past decade. In conjunction there have also been advances in our clinical knowledge that have led to changes in the screening regimen. These changes are expected to continue in the future as CT scanners continue to improve and knowledge about screening accumulates, and computer-assisted techniques are expected to play an ever more important role. This dynamic process will lead to continued improvements in the diagnostic distribution of lung cancers detected under CT screening.

Lung cancer screening with CT: Mayo Clinic experience

PURPOSE

To evaluate a large cohort of patients at high risk for lung cancer by using screening with low-dose spiral computed tomography (CT) of the chest.

MATERIALS AND METHODS

A prospective cohort study was performed with 1,520 individuals aged 50 years or older who had smoked 20 pack-years or more. Participants underwent three annual low-dose CT examinations of the chest and upper abdomen. Characteristics of pulmonary nodules and additional findings were tabulated and analyzed.

RESULTS

Two years after baseline CT scanning, 2,832 uncalcified pulmonary nodules were identified in 1,049 participants (69%). Forty cases of lung cancer were diagnosed: 26 at baseline (prevalence) CT examinations and 10 at subsequent annual (incidence) CT examinations. CT alone depicted 36 cases; sputum cytologic examination alone, two. There were two interval cancers. Cell types were as follows: squamous cell tumor, seven; adenocarcinoma or bronchioloalveolar carcinoma, 24; large cell tumor, two; non-small cell tumor, three; small cell tumor, four. The mean size of the non-small cell cancers detected at CT was 15.0 mm. The stages were as follows: IA, 22; IB, three; IIA, four; IIB, one; IIIA, five; IV, one; limited small cell tumor, four. Twenty-one (60%) of the 35 non-small cell cancers detected at CT were stage IA at diagnosis. Six hundred ninety-six additional findings of clinical importance were identified.

CONCLUSION

CT can depict early-stage lung cancers. The rate of benign nodule detection is high.

Screening for early lung cancer with low-dose spiral CT: prevalence in 817 asymptomatic smokers

PURPOSE

To present prevalence screening data from a nonrandomized screening trial by using low-dose computed tomography (CT) and a simple algorithm based on the size and attenuation of detected nodules to guide diagnostic work-up.

MATERIALS AND METHODS

Eight hundred seventeen asymptomatic volunteers (age range, 40-78 years; median age, 53 years; median tobacco consumption, 45 pack-years) underwent spiral low-dose CT of the chest without contrast material enhancement. We regarded all noncalcified pulmonary nodules greater than 10 mm in diameter as potentially malignant and recommended histologic examination or follow-up after 3, 6, 12, and 24 months to exclude growth. For noncalcified pulmonary nodules of 10 mm or smaller, repeat low-dose CT was recommended to exclude growth.

RESULTS

In 43% (350 of 817) of individuals, 858 noncalcified pulmonary nodules were found. Thirty-two nodules in 29 subjects were larger than 10 mm. Biopsy of 15 lesions revealed lung cancer in 12 lesions in 11 subjects (prevalence for all ages, 1.3% [11 of 817 subjects]; >50 years of age, 2.1% [11 of 519 subjects]; >60 years of age, 3.9% [eight of 206 subjects]), with a high proportion of early tumor stages (seven tumors, stage I; two, stage II; and three, stage III); three lesions were benign. In 17 nodules larger than 10 mm, follow-up with low-dose CT for a minimum of 24 months did not demonstrate growth.

CONCLUSION

Lung cancer screening with low-dose CT demonstrated a prevalence of asymptomatic cancers in 1.3% of a smoking population, including a high proportion of early tumor stages and a 20% (three of 15) rate of invasive procedures for benign lesions.

Computed tomography screening for lung cancer

The development of CT technology reopened the lung cancer screening debate. Computed tomography screening for lung cancer certainly meets all the criteria required for an appropriate screening test. First and perhaps most importantly, the disease for which the screening is being performed should have a significant prevalence in the population being studied and be a significant health risk for those afflicted with it. Lung cancer is the leading cause of cancer death in both men and women, and one of the most lethal of all cancers.

Screening for lung cancer with low-dose spiral computed tomography

Studies suggest that screening with spiral computed tomography can detect lung cancers at a smaller size and earlier stage than chest radiography can. To evaluate low-radiation-dose spiral computed tomography and sputum cytology in screening for lung cancer, we enrolled 1,520 individuals aged 50 yr or older who had smoked 20 pack-years or more in a prospective cohort study. One year after baseline scanning, 2,244 uncalcified lung nodules were identified in 1,000 participants (66%). Twenty-five cases of lung cancer were diagnosed (22 prevalence, 3 incidence). Computed tomography alone detected 23 cases; sputum cytology alone detected 2 cases. Cell types were: squamous cell, 6; adenocarcinoma or bronchioalveolar, 15; large cell, 1; small cell, 3. Twenty-two patients underwent curative surgical resection. Seven benign nodules were resected. The mean size of the non-small cell cancers detected by computed tomography was 17 mm (median, 13 mm). The postsurgical stage was IA, 13; IB, 1; IIA, 5; IIB, 1; IIIA, 2; limited, 3. Twelve (57%) of the 21 non-small cell cancers detected by computed tomography were stage IA at diagnosis. Computed tomography can detect early-stage lung cancers. The rate of benign nodule detection is high.

Early lung cancer action project: annual screening using single-slice helical CT

The advent of helical CT imaging held promise for the early diagnosis, and thereby, for enhanced curability of lung cancer--a highly fatal disease. In 1993, the Early Lung Cancer Action Project (ELCAP) was initiated and experimentally screened a cohort of 1,000 high-risk persons. Here we summarize the results of the baseline and annual repeat CT screening of these 1,000 subjects. CT-based screening (compared to traditional radiology) was clearly shown to enhance the detection of lung cancer at earlier and more curable stages. A discussion follows of the meaning of the results and possible future screening protocols.

Early lung cancer action project: a summary of the findings on baseline screening

PURPOSE

The Early Lung Cancer Action Project (ELCAP) is designed to evaluate baseline and annual repeat screening by low radiation dose computed tomography (low-dose CT) in persons at high-risk for lung cancer.

METHODS

Since starting in 1993, the ELCAP has enrolled 1,000 asymptomatic persons, 60 years of age or older, with at least 10 pack-years (1 pack per day for 10 years, or 2 packs per day for 5 years) of cigarette smoking, no prior cancer, and medically fit to undergo thoracic surgery. After a structured interview and informed consent, baseline chest radiographs and low-dose CT were obtained on each subject. The diagnostic work-up of screen-detected noncalcified pulmonary nodules (NCN) was guided by ELCAP recommendations which included short-term high-resolution CT follow-up for the smallest nodules. Baseline

RESULTS

On low-dose CT at baseline compared to chest radiography, NCN were detected three times as commonly (23% versus 7%), malignancies four times as commonly (2.7% versus 0.7%), and stage I malignancies six times as commonly (2.3% versus 0.4%). Of the 27 CT-detected cancers, 96% (26/27) were resectable; 85% (23/27) were stage I, and 83% (19 of the 23 stage I) were not seen on chest radiography. Following the ELCAP recommendations, biopsies were performed on 28 of the 233 subjects with NCN; 27 had a malignant and one a benign NCN. Another three individuals underwent biopsy outside of the ELCAP recommendations; all had benign NCNS: No one had thoracotomy for a benign nodule.

CONCLUSION

Baseline CT screening for lung cancer provides for detecting the disease at earlier and presumably more commonly curable stages in a cost-effective manner.

Early lung cancer action project: initial findings on repeat screenings

BACKGROUND

The Early Lung Cancer Action Project (ELCAP) was designed to evaluate the usefulness of annual computed tomography (CT) screening for lung carcinoma. With the baseline results having been reported previously, the focus of the current study was on the early results of the repeat screenings.

METHODS

A cohort of 1000 high-risk individuals was recruited for baseline and annual repeat CT screening. At last follow-up, a total of 1184 annual repeat screenings had been performed. A positive result from the screening test was defined as newly detected, one to six noncalcified pulmonary nodules with interim growth. The diagnostic workup of the individuals was guided by recommendations supplied by the ELCAP investigators to the collaborating clinicians.

RESULTS

Of the 1184 repeat CT screenings, the test result was positive in 30 (2.5%). In 2 of these 30 cases, the individual died (of an unrelated cause) before diagnostic workup and the nodule(s) resolved in another 12 individuals. In the remaining 16 individuals, the absence of further growth was documented by repeat CT in 8 individuals and further growth was documented in the remaining 8 individuals. All eight individuals with further nodular growth underwent biopsy and malignancy was diagnosed in seven. Six of these seven malignancies were nonsmall cell carcinomas (five of which were Stage IA and one of which was Stage IIIA) and the one small cell carcinoma was found to be of limited stage. The median size dimension of these malignancies was 8 mm. In another two subjects, symptoms prompted the interim diagnosis of lung carcinoma. Neither of these malignancies was nodule-associated but rather were endobronchial; one was a Stage IIB nonsmall cell carcinoma and the other was a small cell carcinoma of limited stage.

CONCLUSIONS

False-positive screening test results are uncommon and usually manageable without biopsy; compared with no screening, such screenings permit diagnosis at substantially earlier and thus more curable stages. Annual repetition of CT screening is sufficient to minimize symptom-prompted interim diagnoses of nodule-associated malignancies.

Results of three-year mass screening programme for lung cancer using mobile low-dose spiral computed tomography scanner

The aim of this study was to evaluate the usefulness of annual screening for lung cancer by low-dose computed tomography (CT) and the characteristics of identified lung cancers. Subjects consisted of 5483 general population aged 40-74 years, who received initial CT scans in 1996, followed by repeat annual scans for most subjects in 1997 and 1998, with a total of 13 786 scans taken during 1996-1998. Work-up examinations for patients with suspicious lesions were conducted using diagnostic CTs. The initial screening in 1996 detected suspicious nodules in 279 (5.1%) of 5483 subjects, and 22 (8%) were confirmed surgically to have lung cancer. Corresponding figures in 1997 and 1998 screening studies were 173 (3.9%) of 4425 and 25 (14%) of 173, and 136 (3.5%) of 3878 and 9 (7%) of 136, respectively. The sensitivity and specificity of detecting surgically confirmed lung cancer were 55% (22/40) and 95% (4960/5199) in 1996 and 83% (25/30) and 97% (4113/4252) in 1997 screening, respectively. 88% (55/60) of lung cancers identified on screening and surgically confirmed were AJCC stage IA. Our trial allowed detection of nearly 11 times the expected annual number of early lung cancers. Repeat CT allowed the detection of more aggressive, rapidly growing lung cancers, compared to those in the initial screening.

Small pulmonary nodules: volumetrically determined growth rates based on CT evaluation

PURPOSE

To determine the accuracy of high-resolution computed tomographic (CT) volumetric measurements of small pulmonary nodules to assess growth and malignancy status.

MATERIALS AND METHODS

The accuracy of three-dimensional (3D) image extraction and isotropic resampling techniques was assessed by performing three experiments. The first experiment measured volumes in spherical synthetic nodules of two diameters (3.20 and 3.96 mm), the second measured deformable silicone synthetic nodules prior to and after their shape had been altered markedly, and the third measured nodules of various shapes and sizes. Three-dimensional techniques were used to assess growth in 13 patients for whom the final diagnosis was known and whose initial nodule diameters were less than 10 mm. By using the exponential growth model and the calculated nodule volume at two points in time, the doubling time for each subject was calculated.

RESULTS

The three synthetic nodule studies revealed that the volume could be measured accurately to within +/-3%. All five malignant nodules grew, and all had doubling times less than 177 days. Some malignant nodules had asymmetric patterns of growth identified by using the 3D techniques but not the two-dimensional methods. All eight benign nodules had doubling times of 396 days or greater or showed a decrease in volume.

CONCLUSION

CT volumetric measurements are highly accurate for determining volume and are useful in assessing growth of small nodules and calculating their doubling times.

CT screening for lung cancer

Recommendations against screening for lung cancer were based on the lack of a reduction in mortality of the screened group as compared with the control group in randomized control trials. These results were interpreted as showing that early detection of lung cancer as a result of screening did not decrease the mortality rate compared with detection after presentation of symptoms for the populations being screened. Evidence, however, shows that earlier-stage intervention leads to substantially higher rates of survival. Screening, therefore, is an effective means to prevent deaths from this otherwise fatal disease. This article discusses the evidence of both CT and chest radiograph screening.

Small solitary pulmonary nodules

We now are detecting an increasing number of SPN that are difficult to diagnose. Many of the techniques we traditionally have relied on were developed when the average size of detected nodules was larger, and these techniques are of limited diagnostic usefulness for small nodules. In the past, recognition of the need for noninvasive differentiation between benign and malignant nodules led to the development of many useful diagnostic techniques. The ever increasing number of small nodules now being detected will stimulate new approaches. In the future, as in the past, many of these will be based on previously developed concepts. Because a majority of these small nodules will be benign, it will be important to develop reliable methods of determining which patients need further evaluation both from a patient management and cost-effectiveness perspective. Criteria will need to be developed based on the initial CT appearance of the nodule, clinical information about the patient, and subsequent CT using the latest decision analytic techniques and databases. Finally, increased interest in predicting the aggressiveness of a lung cancer, once it has been discovered, could lead to further changes in staging criteria.

Screening for lung cancer

Screening for lung cancer has remained controversial since the completion, more than two decades ago, of the three large randomized controlled trials, sponsored by the National Cancer Institute, which led to the recommendation against screening by major medical organizations. Details of the controversy are given, which include concerns about the study design, implementation, and analysis. New evidence about the potential benefit of screening with chest radiography that has emerged since the completion of those trials is reviewed, as well as the results of studies of CT screening for lung cancer.

Early Lung Cancer Action Project: overall design and findings from baseline screening

BACKGROUND

The Early Lung Cancer Action Project (ELCAP) is designed to evaluate baseline and annual repeat screening by low-radiation-dose computed tomography (low-dose CT) in people at high risk of lung cancer. We report the baseline experience.

METHODS

ELCAP has enrolled 1000 symptom-free volunteers, aged 60 years or older, with at least 10 pack-years of cigarette smoking and no previous cancer, who were medically fit to undergo thoracic surgery. After a structured interview and informed consent, chest radiographs and low-dose CT were done for each participant. The diagnostic investigation of screen-detected non-calcified pulmonary nodules was guided by ELCAP recommendations, which included short-term high-resolution CT follow-up for the smallest non-calcified nodules.

FINDINGS

Non-calcified nodules were detected in 233 (23% [95% CI 21-26]) participants by low-dose CT at baseline, compared with 68 (7% [5-9]) by chest radiography. Malignant disease was detected in 27 (2.7% [1.8-3.8]) by CT and seven (0.7% [0.3-1.3]) by chest radiography, and stage I malignant disease in 23 (2.3% [1.5-3.3]) and four (0.4% [0.1-0.9]), respectively. Of the 27 CT-detected cancers, 26 were resectable. Biopsies were done on 28 of the 233 participants with non-calcified nodules; 27 had malignant non-calcified nodules and one had a benign nodule. Another three individuals underwent biopsy against the ELCAP recommendations; all had benign non-calcified nodules. No participant had thoracotomy for a benign nodule.

INTERPRETATION

Low-dose CT can greatly improve the likelihood of detection of small non-calcified nodules, and thus of lung cancer at an earlier and potentially more curable stage. Although false-positive CT results are common, they can be managed with little use of invasive diagnostic procedures.

Neural networks for the analysis of small pulmonary nodules

PURPOSE

Small pulmonary nodules can be readily detected by computed tomography (CT). The goal of this detection is to diagnose early lung cancer as the five year survival at this early stage is over 70% in contradistinction to the overall 5-year survival of around 10%. Critical to the efficacy of CT for early lung cancer detection is the ability to distinguish between benign and malignant nodules. We explored the usefulness of neural networks (NNs) to help in this differentiation.

METHODS

CT images of 28 pulmonary nodules, 14 benign and 14 malignant, each having a diameter less than 3 cm were selected. All were sufficiently malignant in appearance to require needle biopsy and surgery. The statistical-multiple object detection and location system (S-MODALS) NN technique developed for automatic target recognition (ATR) was used to differentiate between these benign and malignant nodules.

RESULTS

S-MODALS was able to correctly identify all but three benign nodules. S-MODALS classified a nodule as malignant because it looked similar to other malignant nodules. It identified the most similar nodules to display them to the radiologist. The specific features of the nodule that determined its classification were also shown, so that S-MODALS is not simply a "black box" technique but gives insight into the NN diagnostics.

CONCLUSION

This initial evaluation of S-MODALS NNs using pulmonary nodules whose CT features were very suspicious for lung cancer demonstrated the potential to reduce the number of biopsies without missing malignant nodules. S-MODALS performed well, but additional optimization of the techniques specifically for CT images would further enhance its performance.

CT surveillance of the thorax in patients with squamous cell carcinoma of the head and neck: a preliminary experience

PURPOSE

Our goal was to determine the number of malignancies detected by thoracic CT in patients with head and neck squamous cell carcinoma (SCCA) in three clinical settings.

METHOD

We retrospectively examined 168 thorax CT scans in 93 patients with head and neck SCCA and determined the number of malignancies (second primary cancers or metastasis) (a) at the time of diagnosis of the primary neck tumor (57 patients), (b) at approximately yearly intervals following treatment of the primary cancer (93 examinations in 43 patients), and (c) at the time of local/regional recurrence of the neck neoplasm (18 patients).

RESULTS

CT detected malignancy in 9 of 57 patients examined during diagnosis of the neck tumor, in 9 of 43 patients during follow-up, and in 6 of 18 patients evaluated at the time of local/regional neck recurrence.

CONCLUSION

Chest CT demonstrates a high number of additional malignancies in patients presenting with advanced SCCA of the head and neck.

The solitary pulmonary nodule: update 1995

PURPOSE

This study analyzed the clinical characteristics, diagnostic evaluation, prevalence of malignancy, and outcome of patients with a solitary pulmonary nodule (SPN) encountered in the outpatient practice of a pulmonologist in an urban university hospital from 1990 to 1993.

PATIENTS AND METHODS

SPN was defined as a round or ovoid density < or = 3 cm in diameter within the lung parenchyma. Patients with and without lung cancer in SPNs were compared.

RESULTS

Forty patients had a mean age of 65 years, an almost equal sex distribution, high prevalences of cardiovascular disease (53%) and chronic obstructive pulmonary disease (COPD) (33%), but a low incidence of tuberculosis. The mean size of SPNs was 1.8 cm. The prevalence of malignancy was 53%. In SPNs < or = 2 cm in diameter, the prevalence of malignancy was 43%. Nonsurgical biopsy techniques made a diagnosis in 78% of patients. In 94% of patients with lung cancer in SPNs, the tumor was resectable (stage 1, 2, or 3A), emphasizing the need for early detection. Despite the small size of the SPNs, the prevalence of malignancy was high.

CONCLUSION

Despite the advanced age and high prevalence of cardiovascular disease and COPD in patients with SPNs, lung cancer that occurs in these lesions appears to have a favorable prognosis if detected promptly.