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

The potential contribution of a computer-aided detection system for lung nodule detection in multidetector row computed tomography

RATIONALE AND OBJECTIVES

We sought to evaluate the potential benefits of a computer-aided detection (CAD) system for detecting lung nodules in multidetector row CT (MDCT) scans.

METHODS

A CAD system was developed for detecting lung nodules on MDCT scans and was applied to the data obtained from 15 patients. Two chest radiologists in consensus established the reference standard. The nodules were categorized according to their size and their relationship to the surrounding structures (nodule type). The differences in the sensitivities between an experienced chest radiologist and a CAD system without user interaction were evaluated using a chi2 analysis. The differences in the sensitivities also were compared in terms of the nodule size and the nodule type.

RESULTS

A total of 309 nodules were identified as the reference standard. The sensitivity of a CAD system (81%) was not significantly different from that of a radiologist (85%; P > 0.05). The sensitivities of the CAD system for detecting nodules < or = 5 mm in diameter as well as detecting isolated nodules were higher than those of a radiologist (83% vs. 75%, P > 0.05; 93% vs. 76%, P < 0.001). The sensitivities of a radiologist for detecting nodules >5 mm and the nodules attached to other structures were higher than those of a CAD system (98% vs. 79%, P < 0.001; 91% vs. 71%, P < 0.001). There were 28.8 false-positive results of CAD per CT study.

CONCLUSION

The CAD system developed in this study performed the nodule detection task in different ways to that of a radiologist in terms of the nodule size and the nodule type, which suggests that the CAD system can play a complementary role to a radiologist in detecting nodules from large CT data sets.

CT screening for lung cancer: five-year prospective experience

PURPOSE

To report results of a 5-year prospective low-dose helical chest computed tomographic (CT) study of a cohort at high risk for lung cancer.

MATERIALS AND METHODS

After informed written consent was obtained, 1520 individuals were enrolled. Protocol was approved by institutional review board and National Cancer Institute and was compliant with Health Insurance Portability and Accountability Act, or HIPAA. Participants were aged 50 years and older and had smoked for more than 20 pack-years. Participants underwent five annual (one initial and four subsequent) CT examinations. A significant downward shift was evaluated in non-small cell lung cancers detected initially from advanced stage down to stage I by using a one-sided binomial test of proportions. Poisson regression and Fisher exact tests were used for comparisons with Mayo Lung Project.

RESULTS

In 788 (52%) men and 732 (48%) women, 61% (927 of 1520) were current smokers, and 39% were former smokers. After five annual CT examinations, 3356 uncalcified lung nodules were identified in 1118 (74%) participants. Sixty-eight lung cancers were diagnosed (31 initial, 34 subsequent, three interval cancers) in 66 participants. Twenty-eight subsequent cases of non-small cell cancers were detected, of which 17 (61%; 95% confidence interval: 41%, 79%) were stage I tumors. Diameter of cancers detected subsequently was 5-50 mm (mean, 14.4 mm; median, 10.0 mm). Analysis for a more than 50% shift in proportion of stage I non-small cell cancer detection did not show statistical significance. Forty-eight participants died of various causes since enrollment. Lung cancer mortality rate for incidence portion of trial was 1.6 per 1000 person-years. There was no significant difference in lung cancer mortality rates of cancers detected in subsequent examinations between this trial and Mayo Lung Project after separation of participants into subsets (2.8 vs 2.0 per 1000 person-years, P = .43).

CONCLUSION

CT allows detection of early-stage lung cancers. Benign nodule detection rate is high. Results suggest no stage shift.

Full-Body Cardiovascular and Tumor MRI for Early Detection of Disease: Feasibility and Initial Experience in 298 Subjects

OBJECTIVE

High diagnostic accuracy, emerging whole-body concepts, and lack of side effects combine to render MRI a natural candidate for screening purposes. The aim of this study was to evaluate the technical feasibility of a comprehensive multiorgan-targeting MRI examination and determine the frequency of findings in subjects without a history of serious disease.

SUBJECTS AND METHODS

The study group was composed of 331 subjects. The MRI protocol (mean examination time, 63 min) encompassed the target organs: the brain, arterial system, heart, and colon. Diagnoses were deemed relevant if the physician had to inform the subject about the findings. Subjects with a history of serious illnesses were excluded from subsequent analysis (n=33). All analyses were performed for the resulting subgroup of 298 subjects (247 men, 51 women; mean age, 49.7 years).

RESULTS

All 298 examinations were diagnostic excluding eight MR colonography components in which remaining stool hampered reliable diagnosis. Follow-up or radiologic confirmation could be obtained in 75% of all cases with relevant findings (128/169); only one false-positive result was encountered. Of the study group, 21% exhibited signs of atherosclerotic disease. Two cerebral infarctions and one myocardial infarction, previously unknown, were encountered; 12% had peripheral vascular disease. Twelve colonic polyps and nine pulmonary lesions were correctly detected. Of all MRI examinations, 29% revealed relevant additional findings in nontargeted organs. Only one minor allergoid reaction was encountered.

CONCLUSION

The presented data point toward an increased use of MRI for screening in the future, but to date screening MRI should not be performed outside a research setting because the cost-benefit relation is unclear.

[Oncologic screening with whole-body MRI: possibilities and limitations]

In the last decade the interest in radiological screening examination increased among informed laymen enormously. Independent from the evidence of whole-body examinations for cancer prevention the discussion about screening must again be considered again due to the newest technical developments, since MRI of the whole-body with high spatial resolution is feasible now within one single examination. The newest system permits simultaneous connection of up to 76 coil elements and signal reception from 32 independent receiving channels. Whole-body MRI including magnetic resonance colonography (MRC) is feasible within 60 min. In this review potential investigation protocols will be presented. Potentials, challenges and limitations of whole-body MRI in the prevention of the malignancies most frequently leading to death are discussed on the basis own experiences examples and the literature.

Cost-effectiveness analysis of screening for lung cancer with low dose spiral CT (computed tomography) in the Australian setting

INTRODUCTION

Low dose spiral computed tomography (CT) is a sensitive screening tool for lung cancer that is currently being evaluated in both non-randomised studies and randomised controlled trials.

METHODS

We conducted a quantitative decision analysis using a Markov model to determine whether, in the Australian setting, offering spiral CT screening for lung cancer to high risk individuals would be cost-effective compared with current practice. This exploratory analysis was undertaken predominantly from the perspective of the government as third-party funder. In the base-case analysis, the costs and health outcomes (life-years saved and quality-adjusted life years) were calculated in a hypothetical cohort of 10,000 male current smokers for two alternatives: (1) screen for lung cancer with annual CT for 5 years starting at age 60 year and treat those diagnosed with cancer or (2) no screening and treat only those who present with symptomatic cancer.

RESULTS

For male smokers aged 60-64 years, with an annual incidence of lung cancer of 552 per 100,000, the incremental cost-effectiveness ratio was 57,325 dollars per life-year saved and 105,090 dollars per QALY saved. For females aged 60-64 years with the same annual incidence of lung cancer, the cost-effectiveness ratio was 51,001 dollars per life-year saved and 88,583 dollars per QALY saved. The model was used to examine the relationship between efficacy in terms of the expected reduction in lung cancer mortality at 7 years and cost-effectiveness. In the base-case analysis lung cancer mortality was reduced by 27% and all cause mortality by 2.1%. Changes in the estimated proportion of stage I cancers detected by screening had the greatest impact on the efficacy of the intervention and the cost-effectiveness. The results were also sensitive to assumptions about the test performance characteristics of CT scanning, the proportion of lung cancer cases overdiagnosed by screening, intervention rates for benign disease, the discount rate, the cost of CT, the quality of life in individuals with early stage screen-detected cancer and disutility associated with false positive diagnoses. Given current knowledge and practice, even under favourable assumptions, reductions in lung cancer mortality of less than 20% are unlikely to be cost-effective, using a value of 50,000 dollars per life-year saved as the threshold to define a "cost-effective" intervention.

CONCLUSION

The most feasible scenario under which CT screening for lung cancer could be cost-effective would be if very high-risk individuals are targeted and screening is either highly effective or CT screening costs fall substantially.

Aspects of computer-aided detection (CAD) and volumetry of pulmonary nodules using multislice CT

With the superb spatial resolution of modern multislice CT scanners and their ability to complete a thoracic scan within one breath-hold, software algorithms for computer-aided detection (CAD) of pulmonary nodules are now reaching high sensitivity levels at moderate false positive rates. A number of pilot studies have shown that CAD modules can successfully find overlooked pulmonary nodules and serve as a powerful tool for diagnostic quality assurance. Equally important are tools for fast and accurate three-dimensional volume measurement of detected nodules. These allow monitoring of nodule growth between follow-up examinations for differential diagnosis and response to oncological therapy. Owing to decreasing partial volume effect, nodule volumetry is more accurate with high resolution CT data. Several studies have shown the feasibility and robustness of automated matching of corresponding nodule pairs between follow-up examinations. Fast and automated growth rate monitoring with only few reader interactions also adds to diagnostic quality assurance.

Impact of low-dose CT on lung cancer screening

Despite advances in therapy, the prognosis of lung cancer remains dismal due to the fact that most cases of lung cancer are diagnosed at advanced stages, when the chance of cure is poor. In cases detected at early stages prognosis is better. Unfortunately, early lung cancer usually causes no symptoms and is, consequently, rarely diagnosed. Therefore, screening for early asymptomatic lung cancer with diagnostic procedures appears promising particularly as risk factors for lung cancer are well known (cigarette smoking, occupational asbestos exposure and others) and screening could, therefore, focus on these risk groups. In the past, screening trials using analysis of sputum cytology and to some extent chest radiography have failed to demonstrate a reduction in lung-cancer mortality with screening, probably due to insufficient sensitivity of these tests for early lung cancer. During the last decade the introduction of spiral computed tomography (CT) has provided a technique with a much higher sensitivity for small lung cancers. Feasibility studies using low-radiation-dose CT demonstrated a high proportion of non-small-cell lung cancer at the initial examination (prevalence) with decreasing numbers of detected cancers at follow-up (incidence). The proportion of early-stage tumors was high both at prevalence and incidence examinations. The rate of invasive procedures for benign lesions was low; most indeterminate lesions could be classified with non-invasive diagnostic approaches. The proportion of interval cancers (cancers diagnosed by symptoms between two screening CT scans) was low. As, however, these one-arm feasibility trials are not appropriate to assess a potential mortality reduction through CT screening, prospective randomised multicenter trials were recently initiated in several countries to analyse the effect of CT screening on lung-cancer mortality.

Lung cancer screening--where we are in 2004 (take home messages)

The best prognosis for lung cancer can be expected by diagnosis at an early stage of the disease. Long-term survival may be improved by increasing the number of early-stage diagnoses. At the present time, three different screening tools for lung cancer are available: Low-dose CT scanning, sputum analysis and fluorescence bronchoscopy. Each of these tools has a different screening target. Low-dose CT scanning focusses on small pulmonary nodules, sputum analysis has the potential of detecting lung cancer of the central airways, and fluorescence bronchoscopy can identify pre-malignancy, carcinoma in situ and minimally invasive squamous cell carcinoma. The best way forward appears to be a combination of all techniques. Sputum analysis can be used to define a better-characterised risk population, and subsequently this population can undergo low-dose CT and fluorescence bronchoscopy.

Computer-assisted detection of pulmonary nodules: evaluation of diagnostic performance using an expert knowledge-based detection system with variable reconstruction slice thickness settings

The purpose of this study was to evaluate the performance of a computer-assisted diagnostic (CAD) tool using various reconstruction slice thicknesses (RST). Image data of 20 patients undergoing multislice CT for pulmonary metastasis were reconstructed at 4.0, 2.0 and 0.75 mm RST and assessed by two blinded radiologists (R1 and R2) and CAD. Data were compared against an independent reference standard. Nodule subgroups (diameter >10, 4-10, <4 mm) were assessed separately. Statistical methods were the ROC analysis and Mann-Whitney U test. CAD was outperformed by readers at 4.0 mm (Az = 0.18, 0.62 and 0.69 for CAD, R1 and R2, respectively; P<0.05), comparable at 2.0 mm (Az = 0.57, 0.70 and 0.69 for CAD, R1 and R2, respectively), and superior using 0.75 mm RST (Az = 0.80, 0.70 and 0.70 and sensitivity = 0.74, 0.53 and 0.53 for CAD, R1 and R2, respectively; P<0.05). Reader performances were significantly enhanced by CAD (Az = 0.93 and 0.95 for R1 + CAD and R2 + CAD, respectively, P<0.05). The CAD advantage was best for nodules <10 mm (detection rates = 93.3, 89.9, 47.9 and 47.9% for R1 + CAD, R2 + CAD, R1 and R2, respectively). CAD using 0.75 mm RST outperformed radiologists in nodules below 10 mm in diameter and should be used to replace a second radiologist. CAD is not recommended for 4.0 mm RST.

Radiologists' performance for differentiating benign from malignant lung nodules on high-resolution CT using computer-estimated likelihood of malignancy

OBJECTIVE

The purpose of our study was to evaluate whether a computer-aided diagnosis (CAD) scheme can assist radiologists in distinguishing small benign from malignant lung nodules on high-resolution CT (HRCT).

MATERIALS AND METHODS

We developed an automated computerized scheme for determining the likelihood of malignancy of lung nodules on multiple HRCT slices; the likelihood estimate was obtained from various objective features of the nodules using linear discriminant analysis. The data set used in this observer study consisted of 28 primary lung cancers (6-20 mm) and 28 benign nodules. Cancer cases included nodules with pure ground-glass opacity, mixed ground-glass opacity, and solid opacity. Benign nodules were selected by matching their size and pattern to the malignant nodules. Consecutive region-of-interest images for each nodule on HRCT were displayed for interpretation in stacked mode on a cathode ray tube monitor. The images were presented to 16 radiologists-first without and then with the computer output-who were asked to indicate their confidence level regarding the malignancy of a nodule. Performance was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

The area under the ROC curve (Az value) of the CAD scheme alone was 0.831 for distinguishing benign from malignant nodules. The average Az value for radiologists was improved with the aid of the CAD scheme from 0.785 to 0.853 by a statistically significant level (p = 0.016). The radiologists' diagnostic performance with the CAD scheme was more accurate than that of the CAD scheme alone (p < 0.05) and also that of radiologists alone.

CONCLUSION

CAD has the potential to improve radiologists' diagnostic accuracy in distinguishing small benign nodules from malignant ones on HRCT.

Detection of pulmonary nodules at multirow-detector CT: effectiveness of double reading to improve sensitivity at standard-dose and low-dose chest CT

The purpose of this study was to assess the effectiveness of double reading to increase the sensitivity of lung nodule detection at standard-dose (SDCT) and low-dose multirow-detector CT (LDCT). SDCT (100 mAs effective tube current) and LDCT (20 mAs) of nine patients with pulmonary metastases were obtained within 5 min using four-row detector CT. Softcopy images reconstructed with 5-mm slice thickness were read by three radiologists independently. Images with 1.25-mm slice thickness served as the gold standard. Sensitivity was assessed for single readers and combinations. The effectiveness of double reading was expressed as the increase of sensitivity. Average sensitivity for detection of 390 nodules (size 3.9+/-3.2 mm) for single readers was 0.63 (SDCT) and 0.64 (LDCT). Double reading significantly increased sensitivity to 0.74 and 0.79, respectively. No significant difference between sensitivity at SDCT and LDCT was observed. The percentage of nodules detected by all three readers concordantly was 52% for SDCT and 47% for LDCT. Although double reading increased the detection rate of pulmonary nodules from 63% to 74-79%, a considerable proportion of nodules remained undetected. No difference between sensitivities at LDCT and SDCT for detection of small nodules was observed.

Flat panel detector-based volumetric CT: prototype evaluation with volumetry of small artificial nodules in a pulmonary phantom

PURPOSE

To evaluate amorphous silicone-based flat panel detector volumetric CT (VCT) in volumetric assessment of small nodules in a pulmonary phantom, and to perform comparative experiments with 4-row multislice CT (MSCT).

MATERIALS AND METHODS

Seventy synthetic nodules (volume range (VR): 0.99-185.77 mm; estimated diameter range (ED): 1.4-7.8 mm) were scanned in spherical shape and after iso-volumetric deformation with VCT and MSCT using 0.63 mm (MSCT I) and 1.25 mm (MSCT II) collimations. Measured volumes and percent measurement errors (PME) were compared between the 3 CT modes before and after nodule deformation. For each measurement pair before and after deformation, the post-deformation relative volumetric inaccuracy (RIA) was determined. Volume, PME, and RIA differences were tested using Wilcoxon and Friedman methods.

RESULTS

The volumes of the smallest nodules (VR = 0.99-2.83 mm, ED = 1.4-1.9 mm) were computable only from VCT scans. In VCT, measured volumes and PMEs before and after deformation differed significantly less compared with MSCT (VCT: P = 0.06 and 0.56, respectively; MSCT I: P = 0.0012 and 0.006, respectively; and MSCT II: P < 0.0001 for measured volumes and PMEs). In VCT PMEs of 5.51-32.21 mm nodules (ED = 2.4-4.1 mm) before and after deformation were significantly below MSCT (VCT averages = 1.43-1.91% and 1.98-3.48%, for spherical and deformed nodules, respectively; MSCT I averages = 9.97-26.1% and 12.16-38.10%, respectively; MSCT II averages = 17.79-46.18 and 18.14-54.66%, respectively, P < 0.0001) and RIAs in VCT were significantly below MSCT (VCT: 0.50-2.62%, MSCT I: 3.35-15.97%, and MSCT II: 4.29-18.46%; P = 0.0001-0.0039).

CONCLUSION

VCT volumetry is highly accurate in volumetry of smallest nodules with estimated diameters of 1.4-4.1 mm.

The effect of tumor size on curability of stage I non-small cell lung cancers

OBJECTIVE

The objective of this study was to determine the relationship between tumor size and curability of stage I non-small cell lung cancer.

METHODS

From the Surveillance, Epidemiology, and End Results registry 2003, we identified all primary non-small cell lung cancer cases that were diagnosed prior to autopsy. Among these cases, we narrowed the focus to those diagnosed in 1988 or later, and to 7,620 patients who had undergone curative surgical resection. Kaplan-Meier survival curves were obtained for these stage I malignancies for five tumor size categories (ie, 5 to 15 mm, 16 to 25 mm, 26 to 35 mm, 36 to 45 mm, and > 45 mm). The 12-year Kaplan-Meier estimator of survival was used as a measure of lung cancer cure rate.

RESULTS

Among 7,620 stage I cancers, cure rates decreased with increasing tumor size. The 12-year survival rates for patients with tumors 5 to 15 mm in diameter was 69% (95% confidence interval [CI], 64 to 74%), 63% for those with tumors 16 to 25 mm in diameter (95% CI, 60 to 67%), 58% for those with tumors 26 to 35 mm in diameter (95% CI, 54 to 61%), 53% for those with tumors 36 to 45 mm in diameter (95% CI, 48 to 57%), and 43% for those with tumors > 45 mm in diameter (95% CI, 39 to 48%). Cure rates were statistically significantly different for all tumor size categories (p < 0.05) except for the groups with tumors 26 to 35 mm and 36 to 45 mm in diameter (p = 0.10).

CONCLUSIONS

Smaller tumor size at diagnosis is associated with improved curability within stage I non-small cell lung cancers. These results suggest that further subclassification by size within stage I may be important.

The feasibility of low-dose CT for pulmonary metastasis in patients with primary gynecologic malignancy

PURPOSE

To assess the feasibility of low-dose CT (LDCT) in the detection of pulmonary metastases in patients with primary gynecologic malignancies and also to compare the performance of chest digital radiography (DR) and LDCT for their delectability of pulmonary metastases, with use of standard-dose CT (SDCT) as the reference standard.

MATERIALS AND METHODS

Thirty female patients with primary gynecologic malignancies (age range, 20-76 years; mean age, 50 years) underwent DR, noncontrast LDCT and contrast-enhanced SDCT, which were performed within an interval of 2 weeks. We used lung nodule, mediastinal lymphadenopathy (>10 mm in the short axis) and pleural changes (including effusion, irregular thickening, or nodularity) as the cardinal imaging findings of lung metastases. A five-point scoring system was designed to indicate the probability of lung metastasis from primary gynecologic malignancies. The five-point scores of DR, LDCT, and SDCT were analyzed by receiver operating characteristic (ROC) curve.

RESULTS

SDCT probability scores of +2 and -2 were set to indicate true positive and true negative for pulmonary nodule, mediastinal lymphadenopathy, and pleural effusion, respectively. All the areas under the ROC curve of LDCT appeared to be larger than those of DR[pulmonary nodule: 0.96 [95% confidence interval (CI): 0.92-1.01] vs. 0.74 [95% CI: 0.57-0.91], 0.82 [95% CI: 0.70-0.95] vs. 0.61 [95% CI: 0.50-0.77]; mediastinal lymphadenopathy: 0.98 [95% CI: 0.93-1.03] vs. 0.90 [95% CI: 0.79-1.01], 0.94 [95% CI: 0.82-1.06] vs. 0.66 [95% CI: 0.44-0.88]; and pleural effusion: 0.98 [95% CI: 0.93-1.03] vs. 0.56 [95% CI: 0.29-0.82], 0.90 [95% CI: 0.74-1.05] vs. 0.46 [95% CI: 0.23-0.68]].

CONCLUSION

The performance of LDCT were comparable to those of SDCT and superior to those of DR for detection of pulmonary nodule, mediastinal lymphadenopathy, and pleural effusion. By using LDCT, there was no need of intravenous contrast injection and less radiation exposure. We propose a protocol including standard-dose abdominal CT and low-dose chest CT for the initial and follow-up stagings of primary gynecologic malignancy. The use of chest DR is unnecessary.

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.

Low-dose chest CT: optimizing radiation protection for patients

OBJECTIVE

The aim of our study was to evaluate CT scanning protocols to determine how best to minimize patient exposure to ionizing radiation while maintaining sufficient image quality to detect pulmonary diseases.

SUBJECT AND METHODS

The CT dose index (CTDI) was determined by scanning an acrylic phantom at various tube current-time products (7.5-115 mAs). Image quality was evaluated by comparing the homogeneity and noise level of CT scans obtained in the acrylic phantom with those obtained in a water-equivalent phantom. The CT scans obtained at various milliampere-second settings in patients with nodules or diffuse opacifications were assessed. The relationships between the CTDI and the image quality of the CT scans (noise level and artifacts) were established.

RESULTS

The reduction of a conventional tube current-time product (115 mAs) by 65%, 78%, or 93.5% can decrease the CTDI by 60%, 70%, or 85%, respectively. In correlating the image quality of each CT scan to the milliampere-second settings used to obtain it, we found that homogeneity decreased as milliampere-second settings decreased, whereas the noise level increased as milliampere-second settings decreased. For both 8- and 3-mm slice thicknesses, the homogeneity of CT scans acquired at 7.5 mAs or greater was within the acceptable range (< 4 H). However, the noise level of CT scans remained within the acceptable range (< 0.35%) when 25 mAs or greater was used. The evaluation of the image quality of the patients' CT scans indicated no statistical significance in image quality rating between the scans obtained at 25 mAs and those obtained at 115 mAs (p > 0.01).

CONCLUSION

Low-dose (i.e., 40 or 25 mAs) helical chest CT produced satisfactory image quality and reduced the CTDI, thereby maximally protecting patients from radiation exposure.

Screening for lung cancer: current status and future directions: Thomas A. Neff lecture

Lung cancer is the number one cancer killer in North America. Currently, screening for lung cancer is not recommended. Therefore, patients will not receive a diagnosis until they present with symptomatic disease, which is usually advanced stage disease. Previous trials of screening with chest roentgenograms and sputum cytology have failed to show a decrease in lung cancer mortality. Some reports of screening with low-dose spiral CT scans have detected lung cancers at a smaller size (average size, 1.5 cm) than those usually detected by chest radiographs (mean size, 3.0 cm). Spiral CT scanning has been shown to detect between 58% and 85% of non-small cell lung cancers (NSCLCs) while they are in stage IA, and this compares favorably to the current medical practice, in which only 15% are detected as localized disease (Surveillance, Epidemiology, and End Results study data). This article summarizes the spiral CT screening data, and reviews some of the data related to screening with sputum cytology, sputum methylation, and autofluorescence bronchoscopy. Last, there is a brief discussion of some promising future strategies, with emphasis and data from studies presented at this Aspen Lung Conference.

Non-cardiac findings on coronary electron beam computed tomography scanning

The objective of this study was to estimate the prevalence and significance of non-cardiac findings on Electron Beam Computed Tomography (EBT) scanning when used in population screening for the quantitative measurement of coronary artery calcium and estimate of coronary risk. Clinic files of 1366 subjects who underwent EBT scanning between September 1996 and December 1998 at the University of Pittsburgh affiliated Comprehensive Heart Care Center were abstracted. The files of 1356 subjects contained the calcium score and non-cardiac findings as reported by board-certified radiologists, who interpreted the scans during the period 1996-1998. A National Death Index (NDI) Plus match was performed to ascertain cause of death. Two hundred seventy-eight of 1356 (20.5%) subjects had 1 or more non-cardiac findings on EBT scanning. Fifty-seven of 1356 (4.2%) received a recommendation for diagnostic CT follow-up. Forty-six of the 57 recommendations were for pulmonary nodules and 11 were for non-nodule, non-cardiac findings. Seven members of the cohort died during a short follow-up period. In 1 case, the non-cardiac finding was the cause of death. Non-cardiac findings in a healthy cohort referred for EBT coronary screening are relatively common. Findings range from clinically insignificant to the cause of death during a short follow-up period. EBT scanning is a frequently used coronary screening procedure. With the relatively high detection of significant, non-cardiac pathology in this increasingly common screening procedure, consideration should be given for radiologists to interpret the scans.

Computer-assisted detection of pulmonary nodules: performance evaluation of an expert knowledge-based detection system in consensus reading with experienced and inexperienced chest radiologists

To evaluate the performance of experienced versus inexperienced radiologists in comparison and in consensus with an interactive computer-aided detection (CAD) system for detection of pulmonary nodules. Eighteen consecutive patients (mean age: 62.2 years; range 29-83 years) prospectively underwent routine 16-row multislice computed tomography (MSCT). Four blinded radiologists (experienced: readers 1, 2; inexperienced: readers 3, 4) assessed image data against CAD for pulmonary nodules. Thereafter, consensus readings of readers 1+3, reader 1+CAD and reader 3+CAD were performed. Data were compared against an independent gold standard. Statistical tests used to calculate interobserver agreement, reader performance and nodule size were Kappa, ROC and Mann-Whitney U. CAD and experienced readers outperformed inexperienced readers (Az=0.72, 0.71, 0.73, 0.49 and 0.50 for CAD, readers 1-4, respectively; P<0.05). Performance of reader 1+CAD was superior to single reader and reader 1+3 performances (Az=0.93, 0.72 for reader 1+CAD and reader 1+3 consensus, respectively, P<0.05). Reader 3+CAD did not perform superiorly to experienced readers or CAD (Az=0.79 for reader 3+CAD; P>0.05). Consensus of reader 1+CAD significantly outperformed all other readings, demonstrating a benefit in using CAD as an inexperienced reader replacement. It is questionable whether inexperienced readers can be regarded as adequate for interpretation of pulmonary nodules in consensus with CAD, replacing an experienced radiologist.

Screening for lung cancer: a review

PURPOSE OF REVIEW

After the disappointing results of lung cancer screening trials conducted in the 1960s to the 1980s, a renewed interest in lung cancer screening emerged in the 1990s with the development of new technologies such as low-dose spiral CT. The literature regarding screening with biomarkers and CT continues to expand rapidly.

RECENT FINDINGS

Although the specificity of CT screening is relatively poor, the sensitivity for the detection of early-stage cancers, particularly adenocarcinoma, is considerably superior to that of chest radiography used in older screening trials. The results of uncontrolled cohort studies of CT screening are promising, but such studies are susceptible to screening biases such as overdiagnosis.

SUMMARY

There is insufficient evidence to support widespread screening in current practice. However, randomized controlled trials are now being conducted to determine whether improved detection by CT will translate into reduced lung cancer mortality. Alternative approaches to secondary prevention such as screening with biomarkers, autofluorescence bronchoscopy, and chemoprevention hold great promise for the future but await further development and evaluation in prospective trials.

Population screening for lung cancer

The feasibility of diagnosing small stage 1 lung cancers using low-dose chest computed tomography in asymptomatic at-risk individuals has been demonstrated in multiple studies. However, it has yet to be proved that the introduction of a chest computed tomography screening programme would do more good than harm at an acceptable cost.

HASTE MRI Versus Chest Radiography in the Detection of Pulmonary Nodules: Comparison with MDCT

OBJECTIVE

The purpose of our study was to compare the diagnostic accuracy of an ultrafast ECG-triggered black blood-prepared HASTE sequence with chest radiography for the detection of pulmonary nodules. SUBJECTS AND METHODS. Sixty-four patients with various primary malignancies who had undergone radiography and MDCT of the chest also underwent ECG-triggered black blood-prepared HASTE MRI of the lung. MR images and radiographs were interpreted separately. The number, location, and size of detected lesions were recorded, and each hemithorax was classified as affected or not affected on the basis of a grade reflecting the conspicuity of nodular involvement. Sensitivity, specificity, and positive and negative predictive values for the detection of pulmonary nodules with diameters of 5 mm or larger were determined, using MDCT findings as the standard of reference. Lesions with diameters smaller than 5 mm were not evaluated. Additional lesion-by-lesion comparisons between MDCT and MRI findings were performed.

RESULTS

MDCT confirmed pulmonary lesions in 32 patients, whereas HASTE MRI revealed lesions in 30 patients and chest radiography, in 19 patients. MDCT revealed 226 nodules in 32 patients, whereas MRI HASTE revealed 227 lesions in 30 patients. Conspicuity scale-based sensitivity and specificity for chest radiography were 55.8% and 92.4%, respectively, whereas HASTE MRI had a sensitivity of 93.0% and a specificity of 96.2%. Positive and negative predictive values for chest radiography were 80% and 79.3%, respectively, and for HASTE MRI, 93.0% and 96.2%, respectively. The sensitivity of HASTE MRI increased with lesion size, ranging from 94.9% for nodules between 5 and 10 mm in diameter to 100% for lesions exceeding 3 cm in diameter.

CONCLUSION

ECG-triggered black blood-prepared HASTE MRI is reliable for detecting pulmonary nodules exceeding 5 mm and has proven significantly more accurate than conventional chest radiography. The technique appears useful as an adjunct to MRI of the heart, great vessels, or chest, potentially increasing the diagnostic yield of MRI examinations.

Lung cancer screening with low-dose chest CT: current issues

Computed tomography offers many advantages over routine radiographs in screening for lung cancer, and it is clear that low-dose spiral CT screening can more frequently find considerably smaller lung cancers than previous detection tools. Recently, investigators have performed low-dose spiral CT scanning for screening of lung cancer, and have suggested that CT screening can depict lung cancers at smaller sizes and at earlier stages. With technological advances in spiral CT scanners, the detection rate of small noncalcified pulmonary nodules has markedly increased, with higher rates noted with thinner collimation of CT scanning. Unfortunately, the majority of these have proved to be benign, i.e. false positive results. If, even in part, CT features could be found to predict benign nodules without follow-up, the false-positive rate would be reduced, and consequently, the cost, emotional stress, radiation dose, morbidity and mortality associated with interventional procedures would also be reduced. There have been several studies trying to establish reliable CT features for benign lesions in small pulmonary nodules and to determine their outcome. Although these efforts have not completely resolved the issue of false positive results, it is expected that lessons will be learnt on how to manage these small nodules through experience with screening in the near future. Because pulmonary nodules on CT are much more common in Korea than in western countries, the management algorithm for screening CT-detected nodules should be modified according to different circumstances, with consensus among related physicians and radiologists. In addition, to enhance patient care and avoid misunderstanding of inherent limitation of CT screening by the screening subjects, physicians, hospital managers as well as radiologists should provide proper information regarding CT screening to the screenees.

Characterization of small nodules by automatic segmentation of X-ray computed tomography images

OBJECTIVE

To characterize the ability of an automatic lung nodule segmentation algorithm to measure small nodule dimensions and growth rates.

METHODS

A phantom of 20 sets of 6 balls each (11 different nylon balls and 9 acrylic balls) of 1 to 9.5 mm in diameter, in foam, was imaged using x-ray computed tomography with slice thicknesses of 5, 2.5, and 1.25 mm, pitches of 3 and 6, and standard and lung resolution. Measurements consisted of volume and maximum in-plane cross-sectional areas and their derived maximum and effective diameters. Growth rates were simulated using pairs of groups of balls.

RESULTS

Volume measurements overestimate volume, more so for thicker slices. For the largest balls, the error is 60% for 5-mm slices and 20% for 1.25-mm slices. Effective diameter calculated from volume better approximates actual diameter. For area measurements, errors are 0% to 5% for the largest balls, and the effective and actual diameters are closely matched.

CONCLUSIONS

Below 5 mm in diameter, changes in volume should reach 100% for reliable indication of growth. Above 6 mm, the threshold for detecting change is on the order of 25% growth. Even under ideal conditions, results indicate the need for caution when making a diagnosis of malignancy on the basis of volume change.

Automated lung nodule detection at low-dose CT: preliminary experience

Objective

To determine the usefulness of a computer-aided diagnosis (CAD) system for the automated detection of lung nodules at low-dose CT.

Materials and Methods

A CAD system developed for detecting lung nodules was used to process the data provided by 50 consecutive low-dose CT scans. The results of an initial report, a second look review by two chest radiologists, and those obtained by the CAD system were compared, and by reviewing all of these, a gold standard was established.

Results

By applying the gold standard, a total of 52 nodules were identified (26 with a diameter ≤ 5 mm; 26 with a diameter > 5 mm). Compared to an initial report, four additional nodules were detected by the CAD system. Three of these, identified only at CAD, formed part of the data used to derive the gold standard. For the detection of nodules > 5 mm in diameter, sensitivity was 77% for the initial report, 88% for the second look review, and 65% for the CAD system. There were 8.0±5.2 false-positive CAD results per CT study.

Conclusion

These preliminary results indicate that a CAD system may improve the detection of pulmonary nodules at low-dose CT.

Estimate of lung cancer mortality from low-dose spiral computed tomography screening trials: implications for current mass screening recommendations

PURPOSE

Low-dose computed tomography (CT) has been suggested for lung cancer screening. Several observational trials have published their preliminary results, and some investigators suggest that this technique will save lives. There are no mortality statistics, however, and the current study used published data from these trials to estimate the disease-specific mortality in this high-risk population.

PATIENTS AND METHODS

Two nonrandomized CT screening trials were selected from the literature for analysis. The number of trial participants, the number of lung cancers diagnosed per year, and stage distribution of the cancers was recorded. Previously published 5-year survival data were used to calculate the number of predicted lung cancer deaths and estimate the overall lung cancer mortality per 1,000 person-years among participants screened. These statistics were then compared to the previous Mayo Lung Project, which used chest radiographs and sputum cytology for screening high-risk individuals.

RESULTS

This study estimates the lung cancer mortality is 4.1 deaths per 1,000 person-years in the Mayo Clinic CT screening trial, and is 5.5 deaths per 1,000 person-years in the Early Lung Cancer Action Program trial. These data are similar to the lung cancer mortality of 4.4 deaths per 1,000 person-years in the interventional arm, and 3.9 deaths per 1,000 person-years in the usual-care arm of the previous Mayo Lung Project.

CONCLUSION

These data suggest that CT screening could produce similar outcomes to prior chest radiographic trials in this high-risk group. Results from randomized trials are required, however, before the true utility of mass screening with CT for lung cancer can be determined.

CT Screening for Lung Cancer: Suspiciousness of Nodules according to Size on Baseline Scans

PURPOSE

To assess the frequency with which a particular, possibly optimal work-up of noncalcified nodules less than 5.0 mm in diameter identified on initial computed tomographic (CT) images at baseline screening leads to a diagnosis of malignancy prior to first annual repeat screening, compared with a possibly optimal work-up of larger nodules.

MATERIALS AND METHODS

Two series of baseline CT screenings in high-risk people were retrospectively reviewed. The first series (n = 1,000) was performed in 1993-1998; the second (n = 1,897), in 1999-2002. In each series, cases in which the largest noncalcified nodule detected was less than 5.0 mm in diameter and those in which it was 5.0-9 mm were reviewed to determine whether diagnostic work-up prior to first annual repeat screening showed or would have shown nodule growth and led or would have led to a diagnosis based on biopsy or surgical specimens.

RESULTS

The frequency with which malignancy was or could have been diagnosed when the largest noncalcified nodule was less than 5.0 mm in diameter was 0 of 378, whereas when the largest noncalcified nodule was 5.0-9 mm in diameter, the frequency was 13 or 14 of 238. If persons with only nodules smaller than 5.0 mm had merely been referred for first annual repeat screening without immediate further work-up, the referrals for such work-up would have been reduced by 54% (from 817 [28%] to 385 [13%] of 2,897).

CONCLUSION

In modern CT screening for lung cancer at baseline, detected noncalcified nodules smaller than 5.0 mm in diameter do not justify immediate work-up but only annual repeat screening to determine whether interim growth has occurred.

Managing the Small Pulmonary Nodule Discovered by CT

OBJECTIVES

To review the Early Lung Cancer Action Project experience and the medical literature from 1993 to 2003 on detection of the small, noncalcified pulmonary nodule by CT in order to formulate a management algorithm for these nodules.

DESIGN

Prospective noncomparative study of smokers without prior malignancy and a review of the medical literature of CT screening of lung cancer.

INTERVENTIONS

Chest CT and, where appropriate, CT observation for nodule growth, antibiotics, CT-guided fine-needle aspiration (FNA) biopsy, fiberoptic bronchoscopy, and video-assisted thoracoscopic surgery (VATS).

RESULTS

The following factors influence the probability of malignancy in a CT-detected, small, noncalcified pulmonary nodule: size, change in size, age, smoking history, density, number of nodules, gender, circumstance of the CT, spirometry, occupational history, and endemic granulomatous disease. The two diagnostic techniques most useful in evaluating the CT-detected, small, noncalcified nodule are short-term observation of nodule growth by CT and CT-guided FNA. Due to small nodule size and the frequent finding of nonsolid or part-solid nodules, positron emission tomography, fiberoptic bronchoscopy, and VATS were less useful.

CONCLUSIONS

Pulmonologists are frequently asked to evaluate the CT-detected, small, noncalcified nodule invisible on standard chest radiography. Immediate biopsy is justified if the likelihood of cancer is high, but if that likelihood is low or intermediate, a period of observation by CT is appropriate. VATS or thoracotomy are rarely necessary for a diagnosis of lung cancer in the CT-detected small pulmonary nodule.

Screening for lung cancer using low dose CT scanning

BACKGROUND

Lung cancer is the most common cause of cancer related death in Ireland. The majority of lung cancers are inoperable at the time of diagnosis and consequently the overall 5 year survival is less than 10%. The objective of the ProActive Lung Cancer Detection (PALCAD) study was to evaluate whether low dose chest computed tomographic scanning (LDCCT) can detect early stage asymptomatic lung cancer in a high risk urban population.

METHODS

Four hundred and forty nine subjects of median age 55 years (range 50-74) with a median pack year smoking history of 45 years (range 10-160), with no previous cancer history and medically fit to undergo thoracic surgery were recruited. After informed consent, LDCCT was performed on all subjects. Non-calcified nodules (NCNs) of >/=10 mm in diameter were referred for biopsy. Follow up with interval LDCCT at 6, 12 and 24 months to exclude growth was recommended for NCNs <10 mm in diameter.

RESULTS

Six (1.3%) NCNs of >/=10 mm were detected of which one (0.23%) had non-small cell lung cancer stage 1; 145 NCNs of <10 mm were detected in 87 (19.4%) subjects. Mediastinal masses were detected in three subjects (0.7%)-one small cell lung cancer and two benign duplication cysts. Incidental pathology was noted in 276 patients (61.5%), most commonly emphysema and coronary artery calcification.

CONCLUSION

The prevalence of resectable lung cancer detected by LDCCT at baseline screening was low at 0.23%, but there was a high rate of significant incidental pathology.

Pulmonary nodules at chest CT: effect of computer-aided diagnosis on radiologists' detection performance

PURPOSE

To evaluate the effect of computer-aided diagnosis (CAD) on radiologists' detection of pulmonary nodules.

MATERIALS AND METHODS

Fifty chest computed tomographic (CT) examination cases were used. The mean nodule size was 0.81 cm +/- 0.60 (SD) (range, 0.3-2.9 cm). Alternative free-response receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare the observers' performance in detecting nodules with and without use of CAD. Five board-certified radiologists and five radiology residents participated in an observer performance study. First they were asked to rate the probability of nodule presence without using CAD; then they were asked to rate the probability of nodule presence by using CAD.

RESULTS

For all radiologists, the mean areas under the best-fit alternative free-response ROC curves (Az) without and with CAD were 0.64 +/- 0.08 and 0.67 +/- 0.09, respectively, indicating a significant difference (P <.01). For the five board-certified radiologists, the mean Az values without and with CAD were 0.63 +/- 0.08 and 0.66 +/- 0.09, respectively, indicating a significant difference (P <.01). For the five resident radiologists, the mean Az values without and with CAD were 0.66 +/- 0.04 and 0.68 +/- 0.04, respectively, indicating a significant difference (P =.02). At observer performance analyses, there were no significant differences in Az values obtained either without (P =.61) or with (P =.88) CAD between the board-certified radiologists and the residents. For all radiologists, in the detection of pulmonary nodules 1.0 cm in diameter or smaller, the mean Az values without and with CAD were 0.60 +/- 0.11 and 0.64 +/- 0.11, respectively, indicating a significant difference (P <.01).

CONCLUSION

Use of the CAD system improved the board-certified radiologists' and residents' detection of pulmonary nodules at chest CT.

The pitfalls of lung cancer screening

Lung cancer screening has received extensive attention for a number of years. As yet the goal of such a screening programme, a reduction in lung cancer mortality proven by a large randomised controlled trial, has not been achieved. Instead we are left with a number of unanswered questions and practical problems. In addition to the basic requirements for an effective screening programme, this review will identify the main pitfalls in lung cancer screening, with particular reference to multislice computed tomography. The specific difficulties relating to the identification of unimportant disease, the failure to identify important disease successfully, the consequences of investigating and treating identified disease and the financial costs will all be discussed.

Screening for early lung cancer with low-dose spiral computed tomography: results of annual follow-up examinations in asymptomatic smokers

The aim of this study was analysis of incidence results in a prospective one-arm feasibility study of lung cancer screening with low-radiation-dose spiral computed tomography in heavy smokers. Eight hundred seventeen smokers (> or =40 years, > or =20 pack years of smoking history) underwent baseline low-dose CT. Biopsy was recommended in nodules >10 mm with CT morphology suggesting malignancy. In all other lesions follow-up with low-dose CT was recommended. Annual repeat CT was offered to all study participants. Six hundred sixty-eight (81.8%) of the 817 subjects underwent annual repeat CT with a total of 1735 follow-up years. Follow-up of non-calcified nodules present at baseline CT demonstrated growth in 11 of 792 subjects. Biopsy was performed in 8 of 11 growing nodules 7 of which represented lung cancer. Of 174 new nodules, 3 represented lung cancer. The 10 screen-detected lung cancers were all non-small cell cancer (6 stage IA, 1 stage IB, 1 stage IIIA, 2 stage IV). Five symptom-diagnosed cancers (2 small cell lung cancer: 1 limited disease, 1 extensive disease, 3 central/endobronchial non-small cell lung cancer, 2 stage IIIA, 1 stage IIIB) were diagnosed because of symptoms in the 12-month interval between two annual CT scans. Incidence of lung cancer was lower than prevalence, screen-detected cancers were smaller, and stage I was found in 70% (7 of 10) of screen-detected tumors. Only 27% (4 of 15) of invasive procedures was performed for benign lesions; however, 33% (5 of 15) of all cancers diagnosed in the population were symptom-diagnosed cancers (3 central NSCLC, all stage III, 2 SCLC) demonstrating the limitations of CT screening.

Screening for lung cancer

BACKGROUND

While population based screening for lung cancer has not been adopted by most countries, it is not clear whether sputum examinations, chest radiography or newer methods such as computed tomography are effective in reducing mortality from lung cancer.

OBJECTIVES

To determine whether screening for lung cancer using regular sputum examinations or chest radiography or CT chest reduces lung cancer mortality.

SEARCH STRATEGY

Electronic databases (the Cochrane Central Register of Controlled Trials, MEDLINE, PREMEDLINE and EMBASE; 1966 to July 2000) ), bibliographies, hand searching of a journal and discussion with experts were used to identify published and unpublished trials.

SELECTION CRITERIA

Controlled trials of screening for lung cancer using sputum examinations, chest radiography or CT chest.

DATA COLLECTION AND ANALYSIS

Intention to screen analysis was performed. Where there was significant statistical heterogeneity relative risks were reported using the random effects model, but for other outcomes the fixed effect model was used.

MAIN RESULTS

Seven trials were included (6 randomised controlled studies and 1 non-randomised controlled trial) with a total of 245,610 subjects. There were no studies with an unscreened control group. Frequent screening with chest x-rays was associated with an 11% relative increase in mortality from lung cancer compared with less frequent screening (RR 1.11, CI: 1.00-1.23). A non statistically significant trend was observed to reduced mortality from lung cancer when screening with chest x-ray and sputum cytology was compared with chest x-ray alone (RR 0.88, CI:0.74-1.03). Several of the included studies had potential methodological weaknesses. There were no controlled studies of spiral CT.

REVIEWER'S CONCLUSIONS

The current evidence does not support screening for lung cancer with chest radiography or sputum cytology. Frequent chest x-ray screening might be harmful. Further, methodologically rigorous trials are required.

Lung cancer screening: a different paradigm

Thoracic computed tomography (CT) is a sensitive method for detecting early lung cancer but has a high false-positive rate and is not sensitive for detecting central preinvasive and microinvasive cancer. Our hypothesis was that automated quantitative image cytometry (AQC) of sputum cells as the first screening method may improve detection rate by identifying individuals at highest risk for lung cancer. A total of 561 volunteer current or former smokers 50 years of age or older, with a smoking history of more than or equal to 30 pack/years, were studied. Among these, 423 were found to have sputum atypia defined as five cells or more with abnormal DNA content using AQC. Noncalcified pulmonary nodules were found in 46% (259/561). Of the 14 detected cancers, 13 were detected in subjects with sputum atypia-nine by CT and four carcinoma in situ/microinvasive cancers by autofluorescence bronchoscopy. One cancer was detected by CT alone. AQC of sputum cells improved the detection rate of lung cancer from 1.8 to 3.1%. CT scan alone would have missed 29% of the cancers. This screening paradigm shift has the additional potential of reducing the number of initial CT scans by at least 25% with further savings in follow-up investigations and treatment.

Volumetric measurements of pulmonary nodules at multi-row detector CT: in vivo reproducibility

The aim of this study was to assess the in vivo measurement precision of a software tool for volumetric analysis of pulmonary nodules from two consecutive low-dose multi-row detector CT scans. A total of 151 pulmonary nodules (diameter 2.2-20.5 mm, mean diameter 7.4+/-4.5 mm) in ten subjects with pulmonary metastases were examined with low-dose four-detector-row CT (120 kVp, 20 mAs (effective), collimation 4x1 mm, normalized pitch 1.75, slice thickness 1.25 mm, reconstruction increment 0.8 mm; Somatom VolumeZoom, Siemens). Two consecutive low-dose scans covering the whole lung were performed within 10 min. Nodule volume was determined for all pulmonary nodules visually detected in both scans using the volumetry tool included in the Siemens LungCare software. The 95% limits of agreement between nodule volume measurements on different scans were calculated using the Bland and Altman method for assessing measurement agreement. Intra- and interobserver agreement of volume measurement were determined using repetitive measurements of 50 randomly selected nodules at the same scan by the same and different observers. Taking into account all 151 nodules, 95% limits of agreement were -20.4 to 21.9% (standard error 1.5%); they were -19.3 to 20.4% (standard error 1.7%) for 105 nodules <10 mm. Limits of agreement were -3.9 to 5.7% for intraobserver and -5.5 to 6.6% for interobserver agreement. Precision of in vivo volumetric analysis of nodules with an automatic volumetry software tool was sufficiently high to allow for detection of clinically relevant growth in small pulmonary nodules.

Management of Patients at High Risk for Pancreatic Cancer

Because pancreatic cancer patients seldom exhibit disease-specific symptoms until the cancer is at an advanced stage, its diagnosis is a virtual death sentence. Therefore, to make a significant impact on long-term survival for subjects with pancreatic cancer, asymptomatic individuals would have to be screened for premalignant precursors of pancreatic cancer or for asymptomatic pancreatic cancer. A number of formidable obstacles limit the ability of healthcare providers to screen for early neoplastic changes and to make a very early and specific diagnosis of pancreatic cancer. These include lack of a high-risk population for sporadic pancreatic cancer and lack of a simple, noninvasive test sensitive enough to detect small cancers. However, progress is being made in defining various high-risk groups for pancreatic cancer, and improvements in imaging modalities make detection of premalignant lesions and small cancers possible in such individuals. The protocols currently being studied, including use of endoscopic ultrasound and endoscopic retrograde cholangiopancreatography to detect precancerous lesions and small pancreatic cancer in high-risk patients, are still in the research arena and not yet ready for clinical practice.

Detection of pulmonary nodules by multislice computed tomography: improved detection rate with reduced slice thickness

The purpose of this study was to find out if the use of 1.25-mm collimated thin-slice technique helps to detect more small pulmonary lung nodules than the use of 5 mm. A total of 100 patient examinations that allowed a reconstruction of 1.25-mm slice thickness in addition to the standard of 5-mm slices were included in a prospective study. Acquisition technique included four rows of 1-mm slices. Two sets of contiguous images were reconstructed and compared with 1.25- and 5-mm slice thickness, respectively. Two radiologists performed a film-based analysis of the images. The size and the confidence of the seen nodules were reported. We did not perform a histological verification, according to the normal clinical procedure, although it would be optimal regarding research. Statistical analysis was performed by using longitudinal analysis described by Brunner and Langer. In addition, sensitivity, specificity, negative predictive value and positive predictive value were calculated for each reader using the 1.25-mm sections as the gold standard. As an index for concordance the kappa value was used. A value of p<0.05 was regarded as significant. In 37 patients pulmonary nodules were detected. Twenty-four patients showed more than one nodule; among these, 7 patients had disseminated disease and were excluded from the study. Pulmonary nodules larger than 10 mm in size were equally well depicted with both modalities, whereas lesions smaller than 5 mm in size were significantly better depicted with 1.25 mm (p<0.05). Using 1.25 mm as the gold standard, sensitivity for 5-mm reconstruction interval was 88 and 86% for observers A and B, respectively. No false-positive results were reported for 5-mm sections. Interobserver agreement for nodule detection determined for 1.25-mm reconstruction intervals showed a k value of 0.753, indicating a good agreement, and 0.562 for 5-mm reconstruction intervals, indicating a moderate agreement. Brunner and Langer analysis showed significant differences for slice thickness and no significant difference between the observers. Reduced slice thickness demonstrated an improvement of small nodule detection, confidence levels, and interobserver agreement. Application of thin-slice multidetector-row CT may raise the sensitivity for lung nodule detection, although the higher detection rate of smaller nodules has to be evaluated from a clinical perspective and remains problematic about how the detection of small nodules will effect patient outcome.

Low-dose computed tomography screening for lung cancer in a general population

RATIONALE AND OBJECTIVES

To report the detection rate for lung cancers in computed tomography (CT) screening in Japanese adults, and to analyze differences in the appearance of the cancers in non-smokers versus smokers.

MATERIALS AND METHODS

Subjects consisted of 7,847 Japanese adults who received low-dose CT screening at least once in a 3-year period. The detection rate of lung cancers and the correlation of imaging, clinical, and pathologic findings of cancers in non-smokers versus smokers were examined.

RESULTS

The detection rate for lung cancer was 1.1% for both non-smokers (45 of 4,251) and smokers (39 of 3,596). The prevalence of well-differentiated adenocarcinomas was greater in non-smokers (88%; 22 of 25) than in smokers (29%; 4 of 14) (P < .001). The prevalence and incidence of pathologic stage IA disease were greater in non-smokers than in smokers (92%; [22 of 24] vs 58% [7 of 12], and 100% [19 of 19] vs 70% [14 of 20]) (both P < .05). The mean size of the tumors in the non-smokers (12.4 mm) was smaller than that in smokers (18.2 mm) (P < .001). The percentage of cancers categorized as pure or mixed ground-glass opacity (86%; 38 of 44) on CT was greater in non-smokers than in smokers (46%; 16 of 35) (P < .001).

CONCLUSION

Most of the lung cancers in non-smokers were slow-growing adenocarcinomas appearing as faint ground-glass opacities on CT, whereas rapidly growing cancers appearing as solid nodules were more commonly seen in smokers.

Small pulmonary nodules: volume measurement at chest CT--phantom study

Three-dimensional methods for quantifying pulmonary nodule volume at computed tomography (CT) and the effect of imaging variables were studied by using a realistic phantom. Two fixed-threshold methods, a partial-volume method (PVM) and a variable method, were used to calculate volumes of 40 plastic nodules (largest dimension, <5 mm: 20 nodules with solid attenuation and 20 with ground-glass attenuation) of known volume. Tube current times (20 and 120 mAs), reconstruction algorithms (high and low frequency), and nodule characteristics were studied. Higher precision was associated with use of a PVM with predetermined pure nodule attenuation, high-frequency algorithm, and diagnostic CT technique (120 mAs). A PVM is promising for volume quantification and follow-up of nodules.

A systematic review and lessons learned from early lung cancer detection trials using low-dose computed tomography of the chest

BACKGROUND

Computed tomography (CT) screening of the chest has shown promise for early detection of lung cancer, but evidence for a reduction in lung cancer mortality by CT screening is not available.

METHODS

We reviewed 208 articles to synthesize available evidence for efficacy of CT screening in detecting potentially curative stages of lung cancer and for evidence in reducing lung cancer mortality. Other outcomes of interest included detection rate of cancer and of suspicious lesions, histology and stage of cancer at detection, screening-related morbidity, and the identification of populations uniquely suited for CT screening. We identified eight papers that reported the outcomes for CT of the chest in lung cancer screening.

RESULTS

Since none of the studies utilized a control group, quantitative pooling was not done. In two studies, both CT and chest radiography (CXR) were used as screening tools in the same cohorts. A total of 19,107 subjects were screened using CT. The detected prevalence rate for lung cancer ranged from 0.40% to 13.6% and was a function of the subjects' age and smoking history. CT screening resulted in a 3-fold higher detection rate and a 5-fold increase in the rate of resectable cancers compared to CXR. Data on lung cancer and overall mortality and screening-related morbidity and mortality were incomplete. CT screening resulted in selective detection of adenocarcinomas with an approximately 2- to 3-fold oversampling of this histologic subtype. The positive predictive value of CT screening was highest for subjects in the 8th decade of life, and it was virtually nil for those in their 5th decade.

CONCLUSIONS

Evidence regarding lung cancer screening by CT shows that this technology detects earlier-stage and smaller lung cancers with greater frequency than other screening methods. To date, no trials have demonstrated that CT screening leads to a reduction in lung cancer mortality. Until mortality trials are completed, low-dose CT screening should be considered an investigative tool rather than the standard of care.

Lung cancer screening

Low-dose CT screening for lung cancer is a complex and controversial topic. This article reviews the history of lung cancer screening trials and addresses the principles and confounding biases associated with screening. Chest radiography was initially used for lung cancer screening in the 1970s. In the mid-1990s helical single-detector CT came into use, followed by helical multidetector CT, the current method of screening. Results from prevalence studies and a few single-arm incidence studies have raised concerns about overdiagnosis and the high rate of nodule detection. Follow-up studies and further investigation are needed. To this end, a randomized, controlled trial sponsored by the National Cancer Institute is underway to evaluate disease-specific mortality.

[Screening for lung cancer with low-dose spiral CT: results in 150 asymptomatic subjects]

BACKGROUND AND OBJECTIVE

Our aim is to present initial baseline data from a screening trial on low-dose spiral computed tomography (CT). We describe enrollment criteria and a diagnostic algorithm based on initial low-dose CT findings.

SUBJECTS AND METHOD

From September 2000 to May 2001, 150 asymptomatic smokers (age range 40-78 years; mean 55 years) were studied using non-enhanced low-dose spiral CT of the chest. Repeated short-term high resolution CT follow-up was performed for non-calcified pulmonary nodules smaller than 10 mm in diameter. Non-calcified pulmonary nodules 10 mm or larger were considered as potentially malignant and a complementary positron emission tomography (PET) exam was recommended.

RESULTS

54 non-calcified pulmonary nodules were found in 34 out of 141 (24.15%) symptom-free subjects. The diameter was 5 mm or shorter in 24 participants (70.6%), 6-10 mm in 7 (20.6%) and longer than 10 mm in 3 (8.8%) individuals. One patient with a non-calcified pulmonary nodule of at least 10 mm underwent a complementary PET exam, which was positive. Biopsy of this nodule demonstrated lung cancer (squamous cell carcinoma). CT follow-up over one year was decided in the other two subjects having non-calcified pulmonary nodules longer than 10 mm, as no radiographic signs indicative of malignancy were observed in the baseline scan.

CONCLUSION

Following this low-dose CT based screening programme, detection of early-stage lung cancer in asymptomatic subjects at high risk of developing the disease is feasible. Further studies are however necessary to pursue more definitive results.

Indeterminate solitary pulmonary nodules revealed at population-based CT screening of the lung: using first follow-up diagnostic CT to differentiate benign and malignant lesions

OBJECTIVE

We studied the role of the first follow-up diagnostic CT for differentiating benign and malignant lesions in indeterminate solitary pulmonary nodules revealed at CT screening for lung cancer in which a total of 13,786 CT examinations (46% in women and 54% in men; 46% were smokers; mean age, 62 years) were performed.

MATERIALS AND METHODS

We reviewed thin-section CT findings on the initial diagnostic CT (lesion size; percentages of ground-glass-opacity areas of lesion; and presence or absence of lobulation, spiculation, air bronchogram, cavity, satellite lesions, pleural tag, concave margins, polygonal shape, and peripheral subpleural lesion) in 80 pulmonary nodules (36 malignancies and 44 benign lesions) of 80 patients. We evaluated changes in size (regression, no change, or growth) on the first follow-up CT performed 42-120 days (mean, 93 days) after the initial CT.

RESULTS

The greatest accuracy (81%) with 89% sensitivity and 75% specificity for determining malignancy was attained with a combined criterion of growth of lesions or predominantly ground-glass-opacity lesions. Of all criteria that were specific to malignancy, the greatest sensitivity (50%) was achieved with a combination of growth or no change in size of lesions and predominantly ground-glass opacity and no concave margins. Of all criteria that were specific to benign lesions, the greatest sensitivity (45%) was attained with a combination of lesion regression or polygonal shape.

CONCLUSION

Follow-up CT findings were useful, and a combination of findings on initial CT and follow-up CT was optimal for differentiating benign and malignant pulmonary nodules.

Lung nodule detection and characterization with multislice CT

The ability to identify and characterize pulmonary nodules has been dramatically increased by the introduction of multislice CT (MSCT) technology. Using high-resolution sections, MSCT allows considerable improvement in assessing nodule morphology, enhancement patterns, and growth. MSCT also has facilitated the development and potential of clinical application of computer-assisted diagnosis.