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

Screening for lung cancer

OBJECTIVE

The purpose of our review is to discuss the current state of lung cancer screening using CT in the context of defined criteria for effective screening.

CONCLUSION

Although there are hopeful developments in lung cancer screening, a number of unresolved issues must be answered before adopting screening on a large scale. Currently no data exist to suggest that lung cancer screening with CT will result in a decrease in lung cancer mortality.

How to deal with incidentally detected pulmonary nodules less than 10mm in size on CT in a healthy person

The high frequency of non-calcified pulmonary nodules (NCN) <10mm incidentally detected on a multi-detector CT (MDCT) of the chest raises the question of how clinicians and radiologists should deal with these nodules. Management algorithms for solitary pulmonary nodules >10mm do not carry across to sub-centimeter lesions. Purpose of this review is to provide a 10-step approach for routinely detected sub-centimeter NCN on a MDCT in healthy persons in order to be able to make an optimal discrimination between benign and malignant NCNs. Recommendations are primarily based on individual cancer risk, the presence or absence of calcifications and nodule size. In nodules >4-5mm nodule consistency, margin and shape should be taken into account. Next steps in the nodule evaluation are the assessment of localization, nodule number, presence or absence of growth and volume doubling time. Growth is defined as a volume doubling time of 400 days or less, based on volumetry. For nodules <4mm, a follow-up CT at 12 months is recommended in high risk persons, whilst for low-risk persons no follow-up is needed. If no growth is observed at 12 months, no further follow-up is required. For solid, smooth or attached indeterminate NCN between 5 and 10mm we recommend an annual repeat scan, whilst for purely intra-parenchymal nodules a 3-month repeat scan should be made to assess growth. Growing lesions with a volume doubling time <400 days require further work-up and diagnosis, otherwise an annual repeat scan to assess growth is recommended.

Lung cancer screening with CT

Lung cancer is the leading cause of cancer death in the United States. Non-small cell lung cancer accounts for 75% to 80% of all lung cancers. There is an impetus to find a screening test that can detect non-small cell lung cancer in its early preclinical stages, when surgical resection is most likely to reduce lung cancer mortality. Although earlier randomized controlled trials of lung cancer screening using chest radiography and sputum cytology failed to show reduced lung cancer mortality, CT is a much more sensitive test for detecting small lung nodules, and has generated considerable enthusiasm as a potential contemporary screening tool for lung cancer.

Effect of CT scanning parameters on volumetric measurements of pulmonary nodules by 3D active contour segmentation: a phantom study

The purpose of this study is to investigate the effects of CT scanning and reconstruction parameters on automated segmentation and volumetric measurements of nodules in CT images. Phantom nodules of known sizes were used so that segmentation accuracy could be quantified in comparison to ground-truth volumes. Spherical nodules having 4.8, 9.5 and 16 mm diameters and 50 and 100 mg cc(-1) calcium contents were embedded in lung-tissue-simulating foam which was inserted in the thoracic cavity of a chest section phantom. CT scans of the phantom were acquired with a 16-slice scanner at various tube currents, pitches, fields-of-view and slice thicknesses. Scans were also taken using identical techniques either within the same day or five months apart for study of reproducibility. The phantom nodules were segmented with a three-dimensional active contour (3DAC) model that we previously developed for use on patient nodules. The percentage volume errors relative to the ground-truth volumes were estimated under the various imaging conditions. There was no statistically significant difference in volume error for repeated CT scans or scans taken with techniques where only pitch, field of view, or tube current (mA) were changed. However, the slice thickness significantly (p < 0.05) affected the volume error. Therefore, to evaluate nodule growth, consistent imaging conditions and high resolution should be used for acquisition of the serial CT scans, especially for smaller nodules. Understanding the effects of scanning and reconstruction parameters on volume measurements by 3DAC allows better interpretation of data and assessment of growth. Tracking nodule growth with computerized segmentation methods would reduce inter- and intraobserver variabilities.

Radiation dose reduction in chest CT: a review

OBJECTIVE

This article aims to summarize the available data on reducing radiation dose exposure in routine chest CT protocols. First, the general aspects of radiation dose in CT and radiation risk are discussed, followed by the effect of changing parameters on image quality. Finally, the results of previous radiation dose reduction studies are reviewed, and important information contributing to radiation dose reduction will be shared.

CONCLUSION

A variety of methods and techniques for radiation dose reduction should be used to ensure that radiation exposure is kept as low as is reasonably achievable.

Lung cancer screening--comparison of computed tomography and X-ray

Recent studies on lung cancer screening with CT disclosed a discrepancy between its efficiency in detecting early lung cancer and a lack of proof for decreasing mortality from lung cancer. The present study, in a city in Japan where an X-ray screening program is provided, bi-annual CT screening was performed for X-ray screening negative subjects for 4 years. Ten patients with lung cancer were detected among 22,720 person-year subjects (0.044%) through the X-ray screening. Among the X-ray screening-negative subjects, 3305 subjects participated in a CT screening program resulting in the detection of 15 patients with lung cancer (0.454%). All 15 cases detected by CT screening and 5 of the 10 cases detected by X-ray screening were at stage IA. In respect of gender, histological type and CT findings, patients detected by CT screening had a better prognostic profile than those detected by X-ray screening. Survival was significantly better in the former than the latter, both in its entirety comparison and in a comparison limited to patients who underwent surgery. In conclusion, CT screening might have the potential to detect lung cancer with good prognostic factors not limited to early detection. Sufficiently long follow-up time, therefore, would be required to evaluate the efficacy for decreasing lung cancer mortality with CT screening.

Lung cancer: interobserver agreement on interpretation of pulmonary findings at low-dose CT screening

PURPOSE

To evaluate agreement among radiologists on the interpretation of pulmonary findings at low-dose computed tomographic (CT) screening examinations for lung cancer.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. HIPAA guidelines were followed. Sixteen radiologists from the 10 National Lung Screening Trial screening centers of the National Cancer Institute's Lung Screening Study network reviewed image subsets from 135 baseline low-dose screening CT examinations in 135 trial participants (89 men, 46 women; mean age, 62.7 years +/- 5.4 [standard deviation]). Interpretations were classified into one of four of the following categories: noncalcified nodule 4 mm or larger in greatest transverse dimension (positive screening result); noncalcified nodule smaller than 4 mm in greatest transverse dimension (negative screening result); calcified, benign nodule (negative screening result); or no nodule (negative screening result). A recommendation for follow-up evaluation was obtained for each case. Interobserver agreement was evaluated by using the multirater kappa statistic and by using response frequencies and descriptive statistics.

RESULTS

Multirater kappa values ranged from 0.58 (for agreement among all four classifications; 95% confidence interval: 0.55, 0.61) to 0.64 (for agreement on classification as a positive or negative screening result; 95% confidence interval: 0.62, 0.65). The average percentage of reader pairs in agreement on the screening result per case (percentage agreement) was 82%. There was wide variation in the total number of abnormalities detected and classified as pulmonary nodules, with differences of up to more than twofold among radiologists. For cases classified as positive, multirater kappa for follow-up recommendations was 0.35.

CONCLUSION

Interobserver agreement was moderate to substantial; potential for considerable improvement exists. Clinical trial registration no. NCT00047385.

Systematic review of baseline low-dose CT lung cancer screening

The purpose of this systematic review was to provide physicians and patients with a synthesis of the available data and an assessment of the operating characteristics associated with baseline LDCT screening for lung cancer. Various databases, meeting abstracts, clinical trials in progress, and major textbooks for relevant data from 1966 to 2006 were searched for relevant studies. The median value of sensitivity, specificity, positive predictive value and negative predictive value were 81%, 81%, 8% and 99%, respectively. Of the studies that compared LDCT with other lung cancer screening maneuvers, it was found that LDCT detected a greater number of cancerous nodules. On average, 80% of lung cancers detected by baseline LDCT screening were categorized as Stage I cancers. Current data demonstrate that both the operating characteristics of baseline LDCT screening and the relatively high proportion of Stage I cancers detected with LDCT may potentially lead to effective screening programs. However, evidence of reduced mortality and morbidity with the use of LDCT is not established. Therefore, LDCT for lung cancer screening should be considered as investigative and needs to be confirmed by well-designed randomized controlled trials prior to community and institutional implementation.

Evaluation of patients with pulmonary nodules: when is it lung cancer?: ACCP evidence-based clinical practice guidelines (2nd edition)

BACKGROUND

Pulmonary nodules are spherical radiographic opacities that measure up to 30 mm in diameter. Nodules are extremely common in clinical practice and challenging to manage, especially small, "subcentimeter" nodules. Identification of malignant nodules is important because they represent a potentially curable form of lung cancer.

METHODS

We developed evidence-based clinical practice guidelines based on a systematic literature review and discussion with a large, multidisciplinary group of clinical experts and other stakeholders.

RESULTS

We generated a list of 29 recommendations for managing the solitary pulmonary nodule (SPN) that measures at least 8 to 10 mm in diameter; small, subcentimeter nodules that measure < 8 mm to 10 mm in diameter; and multiple nodules when they are detected incidentally during evaluation of the SPN. Recommendations stress the value of risk factor assessment, the utility of imaging tests (especially old films), the need to weigh the risks and benefits of various management strategies (biopsy, surgery, and observation with serial imaging tests), and the importance of eliciting patient preferences.

CONCLUSION

Patients with pulmonary nodules should be evaluated by estimation of the probability of malignancy, performance of imaging tests to characterize the lesion(s) better, evaluation of the risks associated with various management alternatives, and elicitation of patient preferences for treatment.

Limited value of shape, margin and CT density in the discrimination between benign and malignant screen detected solid pulmonary nodules of the NELSON trial

PURPOSE

To evaluate prospectively the value of size, shape, margin and density in discriminating between benign and malignant CT screen detected solid non-calcified pulmonary nodules.

MATERIAL AND METHODS

This study was institutional review board approved. For this study 405 participants of the NELSON lung cancer screening trial with 469 indeterminate or potentially malignant solid pulmonary nodules (>50mm3) were selected. The nodules were classified based on size, shape (round, polygonal, irregular) and margin (smooth, lobulated, spiculated). Mean nodule density and nodule volume were automatically generated by software. Analyses were performed by univariate and multivariate logistic regression. Results were presented as likelihood ratios (LR) with 95% confidence intervals (CI). Receiver operating characteristic analysis was performed for mean density as predictor for lung cancer.

RESULTS

Of the 469 nodules, 387 (83%) were between 50 and 500mm3, 82 (17%) >500mm3, 59 (13%) malignant, 410 (87%) benign. The median size of the nodules was 103mm3 (range 50-5486mm3). In multivariate analysis lobulated nodules had LR of 11 compared to smooth; spiculated nodules a LR of 7 compared to smooth; irregular nodules a LR of 6 compared to round and polygonal; volume a LR of 3. The mean nodule CT density did not predict the presence of lung cancer (AUC 0.37, 95% CI 0.32-0.43).

CONCLUSION

In solid non-calcified nodules larger than 50mm3, size and to a lesser extent a lobulated or spiculated margin and irregular shape increased the likelihood that a nodule was malignant. Nodule density had no discriminative power.

Lung cancer screening with spiral CT: baseline results of the randomized DANTE trial

BACKGROUND

Despite the high survival rates reported for screening-detected cases, the potential of screening of high-risk subjects for reducing lung cancer mortality is still unproven. We herewith present the baseline results of a randomized trial comparing screening for lung cancer with annual spiral computed tomography (CT) versus a yearly clinical review.

METHODS

Male subjects, 60-74 years old, and smokers of 20+ pack-years were enrolled. All participants received a baseline medical examination, chest X-rays (CXR) and sputum cytology upon accrual. Subjects randomized in the spiral CT group received a spiral CT scan at baseline, then yearly for the following 4 years. For controls, a yearly clinical examination was scheduled for the following 4 years.

RESULTS

2472 subjects were randomized (1276 spiral CT arm, 1196 controls). Age, smoking exposure and co-morbid conditions were similar in the two groups. In the spiral CT group, 28 lung cancers were detected, 13 of which were visible in the baseline chest X-rays (overall prevalence 2.2%). Sixteen out of 28 tumours (57%) were stage I, and 19 (68%) were resectable. In the control group, eight cases were detected by the baseline chest X-rays (prevalence rate 0.67%), four (50%) were stage I, and six (75%) were resectable.

CONCLUSIONS

Baseline lung cancer detection rate in the spiral CT arm was higher than in most published studies. The stage I detection rate was increased four-fold by spiral CT versus chest X-rays. However, more tumours in an advanced stage were also detected by CT. The high resection rate of screening-detected patients suggests a possible increase in cure rate. However, longer follow-up is required for definitive conclusions. This trial has been registered at www.Clinicaltrials.gov, registration No. NCT00420862.

Baseline results of the Depiscan study: A French randomized pilot trial of lung cancer screening comparing low dose CT scan (LDCT) and chest X-ray (CXR)

BACKGROUND

Lung cancer has the highest mortality-rate per cancer, with an overall 5-year survival <15%. Several non-randomized studies pointed out the high sensitivity of low dose computed tomography (LDCT) to detect early stage lung cancer. In France, Depiscan, a pilot RCT of LDCT versus chest X-ray (CXR), started on October 2002 to determine the feasibility of enrollment by general practitioners (GPs), investigations and diagnostic procedures by university hospital radiologists and multidisciplinary teams, data management by centralized clinical research assistants, and anticipate the future management of a large national trial.

METHODS

GPs and occupational physicians (OPs) selected and enrolled 1000 subjects in 1 year. Eligible subjects were asymptomatic males or females aged 50-75 years with a current or former cigarette smoking history of >/=15 cigarettes per day for at least 20 years (former smokers having quit <15 years prior to enrollment). Based to randomization, annual LDCT or CXR screenings were planned at baseline and annually for 2 years.

RESULTS

Between October 2002 and December 2004, 765 subjects were enrolled by 89 out of the 232 participating GPs and OPs. Complete clinical and imaging baseline data were available for 621 individuals out of the 765 enrolled, due to 144 noncompliant subjects who withdrew their consent. At least one nodule was detected in 152 out of 336 subjects (45.2%) in the LDCT screening, versus 21 out of 285 subjects (7.4%) in the CXR screening arm. Eight lung cancers were detected in the LDCT arm and one in the CXR arm.

DISCUSSION

This pilot trial allows estimating that non-calcified nodules are 10 [6.36-17.07] times more often detected from LDCT than from CXR. However enrollment by GPs was more difficult than expected with 41% active investigators and a high rate (19%) of noncompliant patients. This experience speaks to the need for a high level of GPs formation and a large, coordinated clinical research team in such a trial.

TRIAL REGISTRATION NUMBER

02526.

Usefulness of low-dose CT in the detection of pulmonary metastasis of gestational trophoblastic tumours

AIM

To determine whether a low-dose spiral chest computed tomography (CT) examination could replace standard-dose chest CT in detecting pulmonary metastases in patients with gestational trophoblastic tumour (GTT).

MATERIALS AND METHODS

In a prospective investigation, 67 chest CT examinations of 39 GTT patients were undertaken. All the patients underwent CT examinations using standard-dose (150 mAs, pitch 1, standard reconstruction algorithm) and low-dose (40 mAs, pitch 2, bone reconstruction algorithm) protocols. Two radiologists interpreted images independently. A metastasis was defined as a nodule within lung parenchyma that could not be attributed to a pulmonary vessel. The number of metastases detected with each protocol was recorded. The size of each lesion was measured and categorized as <5, 5-9.9, and > or = 10 mm. Wilcoxon's signed rank test was used to assess the difference between the numbers of lesion detected by the two protocols.

RESULTS

The CT dose index (CTDI) for the standard-dose and low-dose CT protocols was 10.4 mGy and 1.4 mGy, respectively. One thousand, six hundred, and eighty-two metastases were detected by standard-dose CT, and 1460 lesions by the low-dose protocol. The numbers detected by low-dose CT were significantly less than those detected by standard-dose CT (Z=-3.776, p<0.001), especially for nodules smaller than 5mm (Z=-4.167, p<0.001). However, the disease staging and risk score of the patients were not affected by use of the low-dose protocol.

CONCLUSION

Low-dose chest CT can be used as a staging and follow-up procedure for patients with GTT.

Pulmonary nodule detection on MDCT images: evaluation of diagnostic performance using thin axial images, maximum intensity projections, and computer-assisted detection

This study aimed at evaluating the diagnostic benefits of maximum intensity projections (MIP) and a commercially available computed-assisted detection system (CAD) for the detection of pulmonary nodules on MDCT as compared with standard 1-mm images on lung cancer screening material. Thirty subjects were randomly selected from our database. Three radiologists independently reviewed three types of images: axial 1-mm images, axial MIP slabs, and CAD system detections. Two independent experienced chest radiologists decided which were true-positive nodules. Two hundred eighty-five nodules > or =1 mm were identified as true-positive by consensus of two independent chest radiologists. The detection rates of the three independent observers with 1-mm axial images were 22 +/- 4.8%, 30 +/- 5.3%, and 47 +/- 2.8%; with MIP: 33 +/- 5.4%, 39 +/- 5.7%, and 45 +/- 5.8%; and with CAD: 35 +/- 5.6%, 36 +/- 5.6%, and 36 +/- 5.6%. There was a reading technique effect on the observers' sensitivity for nodule detection: sensitivities with MIP were higher than with 1-mm images or CAD for all nodules (F-values = 0.046). For nodules > or =3 mm, readers' sensitivities were higher with 1-mm images or MIP than with CAD (p < 0.0001). CAD was the most and MIP the less time-consuming technique (p < 0.0001). MIP and CAD reduced the number of overlooked small nodules. As MIP is more sensitive and less time consuming than the CAD we used, we recommend viewing MIP and 1-mm images for the detection of pulmonary nodules.

Detecting early pancreatic cancer: problems and prospects

Pancreatic cancer has a poor prognosis. Improving survival will require diagnosis of early pancreatic cancer, which can be defined based on resectability, size, or curability. Pancreatic cancer progresses from noninvasive precursor lesions to invasive cancer over a variable time period. Retrospective review of computed tomography (CT) scans performed prior to diagnosis suggests that pancreatic cancer resectability may be significantly improved if detected as few as 6 months before clinical diagnosis. Since pancreatic cancer is relatively uncommon, to allow cost-effective screening the populations will have to be enriched for the disease using two "sieves." The first sieve would identify a population of subjects at higher than average risk of pancreatic cancer and the second sieve could be a characteristic phenotype among the members of the high-risk group, an abnormality seen on noninvasive imaging or a serologic marker of early pancreatic cancer. So far two high-risk groups have been targets of screening for pancreatic cancer: hereditary pancreatic cancer kindreds and new-onset diabetes. There is no serologic marker of early pancreatic cancer. Confirmation of diagnosis usually requires invasive procedures such as endoscopic ultrasonography (EUS). Although much work still needs to be done, the developments in the field provide us with hope that screening for early pancreatic cancer could become a reality in the not-so-distant future.

Der solitäre Lungenrundherd

Solitary pulmonary nodules (SPN) are radiologically defined as intraparenchymal lung lesions not bigger then 3 cm. In general all pulmonary nodules should be considered malignant until proven otherwise. Primary peripheral lung cancer is the most common cause, at 40%. The probability that an SPN is malignant increases with patient age. Spiral chest CT is the ideal imaging to indicate the precise anatomical location and expose other pathological findings. Malignant SPN can also persist without change for over 2 years. Only complete histological examination can exclude malignance. Therefore every SPN should be resected in operable patients. The surgical risk of video-assisted pulmonary resection and diagnostic thoracotomy is low. For patients who are not operable, other diagnostic procedures such as transthoracic needle aspiration or positron emission tomography may be helpful.

Lung cancer screening

The result of a lung cancer screening program should be fewer lung cancer-specific deaths in the screened population. Studies evaluating chest imaging as a screening tool for lung cancer have not shown a reduction in lung cancer-specific mortality to date. The ability of institutions using chest imaging to meet the criteria for successful screening programs has also been debated. Contentious issues include the presence of an overdiagnosis bias, the ability to find preclinical disease at a curable point in time, the amount of pseudodisease identified, and the cost-effectiveness of screening programs. Current guidelines remain vague as randomized trials are being completed and technologic advances are occurring. The ultimate face of a successful lung cancer screening program is yet to be defined.

Detección y caracterización del nódulo pulmonar por tomografía computarizada multicorte

Pulmonary nodules are a common finding in routine chest studies. Although there are no pathognomic clinical or radiological signs that enable the exact nature of a pulmonary nodule to be determined, the clinical context and the appropriate characterization of the pulmonary nodule make it possible to reach the correct diagnosis in most cases. This article discusses the most important aspects involved in the use of multislice computed tomography in the noninvasive detection and characterization of pulmonary nodules.

Lung cancer screening: has there been any progress? Computed tomography and autofluorescence bronchoscopy

PURPOSE OF REVIEW

Advances in imaging technologies are currently being explored in the attempt to reduce lung cancer morbidity and mortality by achieving stage shift. We reviewed recent important publications on lung cancer screening.

RECENT FINDINGS

Autofluorescence bronchoscopy has established its important role in the intervention of early central airway lesions. Multidetector computed tomography (CT) and CT-positron emission tomography may facilitate diagnosis of early parenchymal lung lesions. Practical implications of screening are reaching far beyond early diagnostic efforts per se as lead-time, length-time, overdiagnosis biases combined with low specificity of screening tests undermine its cost-effectiveness in the era of healthcare budget constraints.

SUMMARY

Advanced imaging technologies may allow early detection and prudent intervention in some individuals that harbour asymptomatic early lung cancer, but disproportional expenses may be required to sieve out many more individuals at risk to attain stage shift. Confounding co-morbidities and practical hurdles may reduce screening's efficacy as it is plausible that for the majority of smokers, lung cancer may not be the ultimate cause of suffering since 90% of them will not develop lung cancer. This fact remains true despite increased use of noninvasive and minimally invasive technologies for the maximum preservation of quality of life irrespective of whether early intervention is a success or failure.

Small solid noncalcified pulmonary nodules detected by screening chest computed tomography

We aimed to determine the outcome of small (<10 mm) solid noncalcified pulmonary nodules detected by chest computed tomography (CT) scans. Reports of low-dose chest CT scans performed from October 2003 to April 2005 at the Seoul National University Hospital Healthcare System Gangnam Center were reviewed to identify patients with solid noncalcified pulmonary nodules smaller than 10 mm. Partly solid and nonsolid nodules or nodules without follow-up imaging within 1 year were excluded. Records were studied to determine if the initial nodules had changed in size. A total of 3478 chest CT examinations were performed, with 232 patients having small noncalcified nodules (6.7%). One hundred and thirty-eight patients met the criteria (104 men and 34 women) and 213 nodules were identified. The median age was 54 years (range 32-80) and at least 86 patients (62%) were at low to intermediate risk for developing lung cancer. The largest nodule was less than 5 mm in diameter in 87 patients (63%) and 5 mm or more in 51 patients (37%). None of the nodules grew and 29 (14%) decreased in size at follow-up CT scans performed within 12 months. When those individuals at low to intermediate risk for lung cancer were included, solid noncalcified subcentimeter nodules were less frequently found in low-dose CT screening and were nearly unchanged in size when a follow-up CT scan was done within 12 months.

Precision of computer-aided volumetry of artificial small solid pulmonary nodules inex vivoporcine lungs

The purpose of this study was to investigate the precision of CT-based volumetric measurements of artificial small pulmonary nodules under ex vivo conditions. We implanted 322 artificial nodules in 23 inflated ex vivo porcine lungs in a dedicated chest phantom. The lungs were examined with a multislice spiral CT (20 mAs, collimation 16x0.75 mm, 1 mm slice thickness, 0.7 mm increment). A commercial volumetry software package (LungCARE VA70C-W; Siemens, Erlangen, Germany) was used for volume analysis in a semi-automatic and a manual corrected mode. After imaging, the lungs were dissected to harvest the nodules for gold standard determination. The volumes of 202 solitary, solid and well-defined lesions without contact with the pleura, greater bronchi or vessels were compared with the results of volumetry. A mean nodule diameter of 8.3 mm (+/-2.1 mm) was achieved. The mean relative deviation from the true lesion volume was -9.2% (+/-10.6%) for semi-automatic and -0.3% (+/-6.5%) for manual corrected volumetry. The subgroup of lesions from 5 mm to <10 mm in diameter showed a mean relative deviation of -8.7% (+/-10.9%) for semi-automatic volumetry and -0.3% (+/-6.9%) for manually corrected volumetry. We conclude that the presented software allowed for precise volumetry of artificial nodules in ex vivo lung tissue. This result is comparable to the findings of previous in vitro studies.

Automated volumetry of solid pulmonary nodules in a phantom: accuracy across different CT scanner technologies

OBJECTIVES

The accuracy of automated volumetry for pulmonary nodules in a phantom using different CT scanner technologies from single-slice spiral CT (SSCT) to 64-slice multidetector-row CT (MDCT) was compared.

MATERIALS AND METHODS

A lung phantom with 5 different categories of pulmonary nodules was scanned using a single-slice spiral CT, a 4-slice MDCT, a 16-slice MDCT and a 64-slice MDCT. Each category comprised of 7-9 nodules each (total n = 40) with different known volumes. Standard dose and low dose protocols were performed using thin and thick collimation. Image data were reconstructed at the thinnest slice thickness. Data sets were analyzed with a dedicated volumetry software. Volumes of all nodules were calculated and compared.

RESULTS

Mean absolute percentage error (APE) for all nodules was 8.65% (+/-7.29%) for the SSCT, 10.26% (+/-8.25%) for the 4-slice MDCT, 8.19% (+/-7.57%) for the 16-slice MDCT and 7.89% (+/-7.39%) for the 64-slice MDCT. There was statistically significant influence of the scanner type, protocol, anatomic location, and nodule volume on APE, but overall, APEs were comparable.

CONCLUSION

Computer-aided volumetry showed accurate measurements in all tested scanner types. This finding has important implications for nodule assessment and follow-up.

Risk-based selection from the general population in a screening trial: selection criteria, recruitment and power for the Dutch-Belgian randomised lung cancer multi-slice CT screening trial (NELSON)

A method to obtain the optimal selection criteria, taking into account available resources and capacity and the impact on power, is presented for the Dutch-Belgian randomised lung cancer screening trial (NELSON). NELSON investigates whether 16-detector multi-slice computed tomography screening will decrease lung cancer mortality compared to no screening. A questionnaire was sent to 335,441 (mainly) men, aged 50-75. Smoking exposure (years smoked, cigarettes/day, years quit) was determined, and expected lung cancer mortality was estimated for different selection scenarios for the 106,931 respondents, using lung cancer mortality data by level of smoking exposure (US Cancer Prevention Study I and II). Selection criteria were chosen so that the required response among eligible subjects to reach sufficient sample size was minimised and the required sample size was within our capacity. Inviting current and former smokers (quit <or= 10 years ago) who smoked >15 cigarettes/day during >25 years or >10 cigarettes/day during >30 years was most optimal. With a power of 80%, 17,300-27,900 participants are needed to show a 20-25% lung cancer mortality reduction 10 years after randomisation. Until October 18, 2005 11,103 (first recruitment round) and 4,325 (second recruitment round) (total = 15,428) participants have been randomised. Selecting participants for lung cancer screening trials based on risk estimates is feasible and helpful to minimize sample size and costs. When pooling with Danish trial data (n = +/-4,000) NELSON is the only trial without screening in controls that is expected to have 80% power to show a lung cancer mortality reduction of at least 25% 10 years after randomisation.

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.

Profiling tumor-associated antibodies for early detection of non-small cell lung cancer

BACKGROUND

A blood test for non-small cell lung cancer (NSCLC) may be a valuable tool for use in a comprehensive lung cancer screening strategy. Here we report the potential of autoantibody profiling to detect early-stage and occult NSCLC.

METHODS

T7-phage NSCLC cDNA libraries were screened with patient plasma to identify phage-expressed proteins recognized by tumor-associated antibodies. Two hundred twelve immunogenic phage-expressed proteins, identified from 4000 clones, were statistically ranked for their individual reactivity with 23 stage I cancer patient and 23 risk-matched control samples. All 46 samples were used as a training set to define a combination of markers that were best able to distinguish patient from control samples; this set of classifiers was then examined using leave-one-out cross-validation. Markers were then used to predict probability of disease in 102 samples from the Mayo Clinic CT Screening Trial (six prevalence cancer samples, 40 drawn 1 to 5 years before diagnosis, and 56 risk-matched controls).

RESULTS

Measurements of the five most predictive antibody markers in 46 cases and controls were combined in a logistic regression model that yielded area under the receiver operating characteristics curve of 0.99; leave-one-out validation achieved 91.3% sensitivity and 91.3% specificity. In testing this marker set with samples from the Mayo Clinic Lung Screening Trial, we correctly predicted six of six prevalence cancers, 32 of 40 cancers from samples drawn 1 to 5 years before radiographic detection on incidence screening, and 49 of 56 risk-matched controls.

CONCLUSIONS

Antibody profiling may be a useful tool for early detection of NSCLC.

Lung cancer: New surgical approaches

Over the past two decades, many surgical specialties have seen a dramatic shift from large, open operations with wide incisions towards more-minimal incisions and less-invasive procedures. Surgical techniques for lung cancer are no exception, and today, video-assisted thoracic surgical lobectomies are being performed with increasing frequency in large-volume thoracic practices. Despite these new surgical techniques, however, the most substantial innovations that have changed surgical outcomes occurred away from the operative theatre. In lung cancer, in particular, the last 20 years have witnessed the clinical debut of more sophisticated, more elegant and more accurate imaging modalities for improved screening, diagnostic and staging, such as the spiral CT scan, PET scan, PET/CT and the endobronchial ultrasound machine. This technology has been complimented by more targeted chemotherapeutic regimens, novel methods of administering more accurate and more concentrated doses of radiation therapy, and innovative local excisional methods, such as the Cyberknife and radiofrequency ablation. The result has been that surgical excision, although remaining the most effective local therapeutic modality in early-stage lung cancer, is no longer the 'lone ranger' treatment, but rather is part of a complex mosaic of multimodality therapy. As scientific advances continue to be translated into the clinic, this trend will inexorably continue with the advent of a molecular staging system using molecular markers and tumour profiling, which ultimately could enhance our ability to predict tumour chemosensitivity. In this brave new world, however, complete surgical resection of the lung cancer will continue to be critical.

Population screening for lung cancer using computed tomography, is there evidence of clinical effectiveness? A systematic review of the literature

Lung cancer is the leading cause of death among all cancer types in the UK, killing approximately 34 000 people per year. By the time symptoms develop, the tumour is often at an advanced stage and the prognosis is bleak. Treatment at a less advanced stage of disease by surgical resection has been shown to substantially reduce mortality. Screening would be attractive if it could detect presymptomatic lung cancer at a stage when surgical intervention is feasible but has been the subject of scientific debate for the past three decades. The aim of this review was to examine the current evidence on the clinical effectiveness of screening for lung cancer using computed tomography. A systematic literature review searching 15 electronic databases and Internet resources from 1994 until December 2004/January 2005 was carried out. Information was summarised narratively. A total of 12 studies of computed tomography screening for lung cancer were identified including two RCTs and 10 studies of screening without comparator groups. The two RCTs were of short duration (1 year). None examined the effect of screening on mortality compared with no screening. The proportion of people with abnormal computed tomography findings varied widely between studies (5-51%). The prevalence of lung cancer detected was between 0.4% and 3.2% (number needed to screen to detect one lung cancer = 31 to 249). Incidence rates of lung cancer were lower (0.1-1%). Among the detected tumours, a high proportion were stage I or resectable tumours, 100% in some studies. Currently, there is insufficient evidence that computed tomography screening is clinically effective in reducing mortality from lung cancer.

Five-year lung cancer screening experience: CT appearance, growth rate, location, and histologic features of 61 lung cancers

PURPOSE

To retrospectively evaluate the computed tomography (CT)-determined size, morphology, location, morphologic change, and growth rate of incidence and prevalence lung cancers detected in high-risk individuals who underwent annual chest CT screening for 5 years and to evaluate the histologic features and stages of these cancers.

MATERIALS AND METHODS

The study was institutional review board approved and HIPAA compliant. Informed consent was waived. CT scans of 61 cancers (24 in men, 37 in women; age range, 53-79 years; mean, 65 years) were retrospectively reviewed for cancer size, morphology, and location. Forty-eight cancers were assessed for morphologic change and volume doubling time (VDT), which was calculated by using a modified Schwartz equation. Histologic sections were retrospectively reviewed.

RESULTS

Mean tumor size was 16.4 mm (range, 5.5-52.5 mm). Most common CT morphologic features were as follows: for bronchioloalveolar carcinoma (BAC) (n = 9), ground-glass attenuation (n = 6, 67%) and smooth (n = 3, 33%), irregular (n = 3, 33%), or spiculated (n = 3, 33%) margin; for non-BAC adenocarcinomas (n = 25), semisolid (n = 11, 44%) or solid (n = 12, 48%) attenuation and irregular margin (n = 14, 56%); for squamous cell carcinoma (n = 14), solid attenuation (n = 12, 86%) and irregular margin (n = 10, 71%); for small cell or mixed small and large cell neuroendocrine carcinoma (n = 7), solid attenuation (n = 6, 86%) and irregular margin (n = 5, 71%); for non-small cell carcinoma not otherwise specified (n = 5), solid attenuation (n = 4, 80%) and irregular margin (n = 3, 60%); and for large cell carcinoma (n = 1), solid attenuation and spiculated shape (n = 1, 100%). Attenuation most often (in 12 of 21 cases) increased. Margins most often (in 16 of 20 cases) became more irregular or spiculated. Mean VDT was 518 days. Thirteen of 48 cancers had a VDT longer than 400 days; 11 of these 13 cancers were in women.

CONCLUSION

Overdiagnosis, especially in women, may be a substantial concern in lung cancer screening.

Low-dose CT: a useful and accessible tool for the early diagnosis of lung cancer in selected populations

OBJECTIVE

An evaluation is made of the effectiveness of low-dose computed tomography (LDCT) in diagnosing early stage lung cancer in the Autonomous Community of Madrid (Spain).

METHODS

The study comprised subjects over 50 years of age who were active smokers (or who had stopped smoking up to 6 months previously) who smoked more than 30 cigarettes daily for at least 15 years, or 20 cigarettes daily for 20 years, or more than 10packs/year and in contact with asbestos at work. The study group was evaluated using LDCT. For all participants in whom LDCT showed no pathological findings, or in those cases classified as benign, a new LDCT scan was performed 2 years after the first. In case of doubt regarding the benign nature of the findings, an assessment algorithm was applied.

RESULTS

Among the initial 482 candidates in the study group, 466 LDCT scans were performed at baseline, revealing 9 extrapulmonary lesions and 114 pulmonary lesions in 98 subjects. The latter raised diagnostic doubts in 32 cases; of these, 15 were confirmed as benign by high resolution computed tomography (HRCT). In the remaining 17 cases, stage IAp adenocarcinoma was diagnosed at baseline (0.2%). With LDCT after 2 years, an additional four adenocarcinomas were diagnosed-all in stage IAp (0.98%). The complete study, including prevalence cut-off and incidence calculation after 2 years, resulted in the diagnosis of five cancers (1.1%) and two false positive cases (28%).

CONCLUSIONS

The use of low-dose computed tomography in risk groups is valid for the early diagnosis of bronchogenic cancer. Nevertheless, significant problems remain, particularly those associated with false positive interpretations. The results of randomized studies on lung cancer mortality such as the US NLST trial and the Dutch-Belgian NELSON trial have to be awaited before any conclusion regarding the effectiveness of LDCT screening can be drawn.

Computed tomography screening for lung cancer

Results of randomised trials are needed before recommending its adoption

Accuracy of automated volumetry of pulmonary nodules across different multislice CT scanners

The purpose of this study was to compare the accuracy of an automated volumetry software for phantom pulmonary nodules across various 16-slice multislice spiral CT (MSCT) scanners from different vendors. A lung phantom containing five different nodule categories (intraparenchymal, around a vessel, vessel attached, pleural, and attached to the pleura), with each category comprised of 7-9 nodules (total, n = 40) of varying sizes (diameter 3-10 mm; volume 6.62 mm(3)-525 mm(3)), was scanned with four different 16-slice MSCT scanners (Siemens, GE, Philips, Toshiba). Routine and low-dose chest protocols with thin and thick collimations were applied. The data from all scanners were used for further analysis using a dedicated prototype volumetry software. Absolute percentage volume errors (APE) were calculated and compared. The mean APE for all nodules was 8.4% (+/-7.7%) for data acquired with the 16-slice Siemens scanner, 14.3% (+/-11.1%) for the GE scanner, 9.7% (+/-9.6%) for the Philips scanner and 7.5% (+/-7.2%) for the Toshiba scanner, respectively. The lowest APEs were found within the diameter size range of 5-10 mm and volumes >66 mm(3). Nodule volumetry is accurate with a reasonable volume error in data from different scanner vendors. This may have an important impact for intraindividual follow-up studies.

Should we screen for occupational lung cancer with low-dose computed tomography?

OBJECTIVE

The objective of this study was to assess the potential value of screening for occupational lung cancer through the use of low-dose computed tomography (LDCT).

METHODS

A literature review of Medline was conducted to assess: 1) screening studies of occupational lung cancer that used LDCT; 2) screening studies of nonoccupational lung cancer that used LDCT; and 3) position papers of medical professional societies and nongovernmental health organizations that have addressed the value of screening for lung cancer with LDCT.

RESULTS

No screening studies of occupational lung cancer with LDCT were uncovered; however, numerous observational and population-based studies have addressed the value of screening for lung cancer among cigarette smokers. Results of these studies are difficult to interpret in light of numerous biases associated with these types of studies. No randomized, controlled studies on screening for lung cancer have been published at this time. No professional, governmental, or nonprofit health organization recommends screening asymptomatic people at risk of lung cancer with LDCT at this time.

CONCLUSION

In the absence of randomized, controlled studies that can address biases commonly encountered in observational and population-based studies, it is unclear whether LDCT reduces mortality from lung cancer. The National Cancer Institute is sponsoring a randomized, controlled study of over 50,000 current and former smokers with the results expected in 2009.

Computer-aided diagnosis of pulmonary nodules on CT scans: segmentation and classification using 3D active contours

We are developing a computer-aided diagnosis (CAD) system to classify malignant and benign lung nodules found on CT scans. A fully automated system was designed to segment the nodule from its surrounding structured background in a local volume of interest (VOI) and to extract image features for classification. Image segmentation was performed with a three-dimensional (3D) active contour (AC) method. A data set of 96 lung nodules (44 malignant, 52 benign) from 58 patients was used in this study. The 3D AC model is based on two-dimensional AC with the addition of three new energy components to take advantage of 3D information: (1) 3D gradient, which guides the active contour to seek the object surface, (2) 3D curvature, which imposes a smoothness constraint in the z direction, and (3) mask energy, which penalizes contours that grow beyond the pleura or thoracic wall. The search for the best energy weights in the 3D AC model was guided by a simplex optimization method. Morphological and gray-level features were extracted from the segmented nodule. The rubber band straightening transform (RBST) was applied to the shell of voxels surrounding the nodule. Texture features based on run-length statistics were extracted from the RBST image. A linear discriminant analysis classifier with stepwise feature selection was designed using a second simplex optimization to select the most effective features. Leave-one-case-out resampling was used to train and test the CAD system. The system achieved a test area under the receiver operating characteristic curve (A(z)) of 0.83 +/- 0.04. Our preliminary results indicate that use of the 3D AC model and the 3D texture features surrounding the nodule is a promising approach to the segmentation and classification of lung nodules with CAD. The segmentation performance of the 3D AC model trained with our data set was evaluated with 23 nodules available in the Lung Image Database Consortium (LIDC). The lung nodule volumes segmented by the 3D AC model for best classification were generally larger than those outlined by the LIDC radiologists using visual judgment of nodule boundaries.

Attitudes towards screening for lung cancer among smokers and their non-smoking counterparts

BACKGROUND

There has been resurgence of interest in lung cancer screening using low-dose computed tomography. The implications of directing a screening programme at smokers has been little explored.

METHODS

A nationwide telephone survey was conducted. Demographics, certain clinical characteristics and attitudes about screening for lung cancer were ascertained. Responses of current, former and never smokers were compared.

RESULTS

2001 people from the US were interviewed. Smokers were significantly (p < 0.05) more likely than never smokers to be male, non-white, less educated, and to report poor health status or having had cancer, and less likely to be able to identify a usual source of healthcare. Compared with never smokers, current smokers were less likely to believe that early detection would result in a good chance of survival (p < 0.05). Smokers were less likely to be willing to consider computed tomography screening for lung cancer (71.2% (current smokers) v 87.6% (never smokers) odds ratio (OR) 0.48; 95% confidence interval (CI) 0.32 to 0.71). More never smokers as opposed to current smokers believed that the risk of disease (88% v 56%) and the accuracy of the test (92% v 71%) were important determinants in deciding whether to be screened (p < 0.05). Only half of the current smokers would opt for surgery for a screen-diagnosed cancer.

CONCLUSION

The findings suggest that there may be substantial obstacles to the successful implementation of a mass-screening programme for lung cancer that will target cigarette smokers.

Small Pulmonary Nodules: Effect of Two Computer-aided Detection Systems on Radiologist Performance

PURPOSE

To prospectively compare the effects of two computer-aided detection (CAD) systems on the detection of small pulmonary nodules at multi-detector row computed tomography (CT) by using a consensus panel decision as the reference standard.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Multi-detector row CT scans were randomly chosen and prospectively evaluated in 25 patients. Two dedicated CAD systems-ImageChecker CT (R2 Technologies, Sunnyvale, Calif) and Nodule Enhanced Viewing (NEV) (Siemens Medical Solutions, Forchheim, Germany)-were used. Results were interpreted by three radiologists with 1, 3, and 6 years of experience. Images were evaluated without and with CAD software. The reference standard was assessed by a consensus panel consisting of all three radiologists and an adjudicator with 8 years of experience.

RESULTS

A total of 116 pulmonary nodules (average diameter, 3.4 mm; average volume, 32.05 mm3) were found in all data sets during consensus interpretation, which included findings from the CAD software and all radiologists. Overall sensitivity was 73% with ImageChecker CT and 75% with NEV. Overall sensitivity without CAD was 68% for radiologist 1, 78% for radiologist 2, and 82% for radiologist 3. With ImageChecker CT, sensitivity increased to 79% for radiologist 1, 90% for radiologist 2, and 84% for radiologist 3. With NEV, sensitivity increased to 79% for radiologist 1, 90% for radiologist 2, and 86% for radiologist 3. The average number of false-positive findings was six (range, 0-14) with ImageChecker CT and eight (range, 0-22) with NEV.

CONCLUSION

Radiologist performance in the interpretation of multi-detector row CT scans can be improved by using CAD systems, with a reduction in the number of false-negative diagnoses. No statistically significant difference in sensitivity was found between the two CAD systems.

Solitary pulmonary nodule: detection and management

Pulmonary nodules are commonly detected at computed tomography (CT) of the chest. More than 95% are \documentclass[12pt]{minimal} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts,amssymb,amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \DeclareFontFamily{T1}{linotext}{} \DeclareFontShape{T1}{linotext}{m}{n}{<-> linotext}{} \DeclareSymbolFont{linotext}{T1}{linotext}{m}{n} \DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext} \begin{document} $\le $ \end{document} 10 mm; of these more than 95% are benign. Visual detection of pulmonary nodules by human readers is suboptimal, particularly with small nodules \documentclass[12pt]{minimal} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts,amssymb,amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \DeclareFontFamily{T1}{linotext}{} \DeclareFontShape{T1}{linotext}{m}{n}{<-> linotext}{} \DeclareSymbolFont{linotext}{T1}{linotext}{m}{n} \DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext} \begin{document} $\le $ \end{document} 10 mm. Computer-assisted detection can improve sensitivity and diagnostic confidence. Due to the high proportion of malignant lesions in nodules >10 mm immediate, often invasive work-up is required including contrast-enhanced dynamic CT, positron emission tomography (PET) or biopsy. However, in nodules \documentclass[12pt]{minimal} \usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts,amssymb,amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \DeclareFontFamily{T1}{linotext}{} \DeclareFontShape{T1}{linotext}{m}{n}{<-> linotext}{} \DeclareSymbolFont{linotext}{T1}{linotext}{m}{n} \DeclareSymbolFontAlphabet{\mathLINOTEXT}{linotext} \begin{document} $\le $ \end{document} 10 mm the high proportion of benign lesions requires a non-invasive work-up usually based on follow-up with unenhanced CT. Invasive procedures are only required for growing nodules. Stable nodules require further follow-up and decreasing nodules are considered benign.

Computer-aided detection and automated CT volumetry of pulmonary nodules

With use of multislice computed tomography (MSCT), small pulmonary nodules are being detected in vast numbers, constituting the majority of all noncalcified lung nodules. Although the prevalence of lung cancers among such lesions in lung cancer screening populations is low, their isolation may contribute to increased patient survival. Computer-aided diagnosis (CAD) has emerged as a diverse set of diagnostic tools to handle the large number of images in MSCT datasets and most importantly, includes automated detection and volumetry of pulmonary nodules. Current CAD systems can significantly enhance experienced radiologists' performance and outweigh human limitations in identifying small lesions and manually measuring their diameters, augment observer consistency in the interpretation of such examinations and may thus help to detect significantly higher rates of early malignomas and give more precise estimates on chemotherapy response than can radiologists alone. In this review, we give an overview of current CAD in lung nodule detection and volumetry and discuss their relative merits and limitations.

Asbestos Surveillance Program Aachen (ASPA): initial results from baseline screening for lung cancer in asbestos-exposed high-risk individuals using low-dose multidetector-row CT

The purpose of this study was to assess the prevalence of lung cancer in a high-risk asbestos-exposed cohort using low-dose MDCT. Of a population of 5,389 former power-plant workers, 316 were characterized as individuals at highest risk for lung cancer according to a lung-cancer risk model including age, asbestos exposure and smoking habits. Of these 316, 187 (mean age: 66.6 years) individuals were included in a prospective trial. Mean asbestos exposure time was 29.65 years and 89% were smokers. Screening was performed on a 16-slice MDCT (Siemens) with low-dose technique (10/20 mAs(eff.); 1 mm/0.5 mm increment). In addition to soft copy PACS reading analysis on a workstation with a dedicated lung analysis software (LungCARE; Siemens) was performed. One strongly suspicious mass and eight cases of histologically proven lung cancer were found plus 491 additional pulmonary nodules (average volume: 40.72 ml, average diameter 4.62 mm). Asbestos-related changes (pleural plaques, fibrosis) were visible in 80 individuals. Lung cancer screening in this high-risk cohort showed a prevalence of lung cancer of 4.28% (8/187) at baseline screening with an additional large number of indeterminate pulmonary nodules. Low-dose MDCT proved to be feasible in this highly selected population.

Outcome in patients with lung cancer invisible on chest roentgenograms but detected only by helical computed tomography

The aim of this study was to evaluate the prognosis for patients with lung cancer detected by helical CT but not by CXR. One hundred and thirty-seven asymptomatic patients with lung cancer diagnosed by annual mass screening of the chest were enrolled over a 7-year period. Five-year survival rates in patients with lung cancer detected only by helical CT (n = 19: CT-only detection group) and in patients with lung cancer visible by both CXR and helical CT (n = 118: control group) were evaluated, and clinical variables were examined as possible predictors of survival time using the Cox proportional-hazards model. There was a significant difference between the 5-year survival rates in the CT-only detection group and in the control group (80% vs. 39%, log rank: P = 0.0171). The risk of death decreased 77% in CT-only detectable lung cancer (hazard ratio: 0.219, 95% confidence interval: 0.057-0.845, P = 0.0275). Lung cancer could not be seen by CXR because nodules were small or faint (n = 11) or overlapping a shadow of thoracic components (n = 8). The percentage of subsolid nodules (classified as either part-solid or non-solid nodules) was higher in the subgroup with small or faint nodules (82% vs. 25%, P = 0.0423). Helical CT has the ability to detect early lung cancer before the small or faint nodules increase to a size visible on CXR, and patients with lung cancer detected only by helical CT have a better prognosis.

Improving radiologists' recommendations with computer-aided diagnosis for management of small nodules detected by CT

RATIONALE AND OBJECTIVES

To evaluate how computer-aided diagnosis (CAD) can improve radiologists' recommendations for management of possible early lung cancers on CT.

MATERIALS AND METHODS

Twenty-eight lung cancers and 28 benign lesions were employed. Each group of 28 lesions was classified into subgroups of two sizes (9 between 6 and 10 mm and 19 between 11 and 20 mm) and three patterns (8 with pure ground glass opacity [GGO], 12 with mixed GGO and 8 solid lesions). Sixteen radiologists participated in the observer study, first without and then with CAD. Radiologists' recommendations, including (1) follow-up in 12 months, (2) in 6 months, (3) in 3 months, or (4) biopsy, were compared at three levels of their malignancy probability ratings (low: 1%-33%; medium: 34%-66%; high: 67%-99%) for 896 observations (56 lesions by the 16 radiologists) in the two size subgroups and three patterns.

RESULTS

The number of recommendations changed by radiologists by use of CAD was 163 (18%) among all 896 observations. Among these changed recommendations, the fraction showing a beneficial effect from CAD was 68% (111/163), and the fraction showing a beneficial effect regarding biopsy recommendations was 69% (48/70). With CAD, the radiologists' performance regarding biopsy recommendations was significantly improved for 43 lung cancers (31 changed to biopsy versus 12 changed away from biopsy; P = .003) and was also improved for 27 benign lesions (10 changed to biopsy versus 17 changed away from biopsy; P = .18). Most of the cancers with improved recommendations were solid lesions or mixed GGO and relatively large.

CONCLUSION

CAD has the potential to improve the appropriateness of radiologists' recommendations for small malignant and benign lesions on CT scans.

Risk-Benefit Analysis of X-Ray Exposure Associated with Lung Cancer Screening in the Italung-CT Trial

OBJECTIVE

Prior analyses of X-ray exposures in lung cancer screening with CT considered the basic acquisition technique in single-detector scanners and the effects of a lifetime screening regimen, whereas the potential benefit in terms of lives saved was not addressed.

MATERIALS AND METHODS

We determined the total-body effective dose of different acquisition techniques for one single-detector and one MDCT scanner and made projections about the cumulative radiation exposure to smokers undergoing four annual CT examinations on the same scanners in the Italung-CT Trial. Combining these data with estimates of radiation-induced fatal cancer and of the benefit of screening, we calculated the risk-benefit ratio for participants in the trial, ex-smokers, and never-smokers.

RESULTS

The cumulative effective doses per 1,000 subjects were 3.3 Sv using an MDCT scanner and 5.8 or 7.1 Sv using a single-detector scanner. Potential fatal cancers associated with radiation exposure were 0.11 per 1,000 subjects for MDCT scanners and 0.20 or 0.24 for single-detector scanners, which is about 10-100 times lower than the number of expected lives saved by screening assuming a 20-30% lung cancer-specific mortality reduction in current smokers. They were, however, of similar magnitude to the lives saved by screening in never-smokers and former smokers assuming a 10% efficacy of screening.

CONCLUSION

MDCT is associated with lower radiation doses than single-detector CT technology. The risk of radiation dose in the Italung-CT Trial is compensated for by the expected benefit. CT screening for lung cancer should not be offered to never-smokers, whereas its recommendation in former smokers is debatable.

Computer-aided detection in screening CT for pulmonary nodules

OBJECTIVE

Our objective was to evaluate the performance of a computer-aided detection (CAD) system for pulmonary nodule detection using low-dose screening CT images.

MATERIALS AND METHODS

One hundred fifty consecutive low-dose screening CT examinations were independently evaluated by a radiologist and a CAD pulmonary nodule detection system (R2 Technology) designed to identify nodules larger than 4 mm in maximum long-axis diameter. All discrepancies between the two techniques were reviewed by one of another two radiologists working in consensus with the initial interpreting radiologist, and a "true" nodule count was determined. Detected nodules were classified by size, density, and location. The performance of the initial radiologist and the CAD system were compared.

RESULTS

The radiologist detected 518 nodules and the CAD system, 934 nodules. Of the 1,106 separate nodules detected using the two techniques, 628 were classified as true nodules on consensus review. Of the true nodules present, the radiologist detected 518 (82%) of 628 nodules and the CAD, 456 (73%) of 628 nodules. All 518 radiologist-detected nodules were true nodules, and 456 (49%) of 934 of CAD-detected nodules were true nodules. The radiologist missed 110 true nodules that were only detected by CAD. In six patients, these were the only nodules detected in the examination, changing the imaging follow-up protocol. CAD identified 478 lesions that on consensus review were false-positive nodules, a rate of 3.19 (478/150) per patient.

CONCLUSION

CAD detected 72.6% of true nodules and detected nodules in six (4%) patients not identified by radiologists, changing the imaging follow-up protocol of these subjects. In this study, the combined review of low-dose CT scans by both the radiologist and CAD was necessary to identify all nodules.