Small incidental pulmonary nodules: how useful is short-term interval CT follow-up?

Lung cancer in patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic lung disease of unknown etiology. With a gradually increasing worldwide prevalence and a mortality rate exceeding that of many cancers, IPF diagnosis and management are critically important and require a comprehensive multidisciplinary approach. This approach also involves assessment of comorbid conditions, such as lung cancer, that exerts a dramatic impact on disease survival. Emerging evidence suggests that progressive lung scarring in the context of IPF represents a risk factor for lung carcinogenesis. Both disease entities present with major similarities in terms of pathogenetic pathways, as well as potential causative factors, such as smoking and viral infections. Besides disease pathogenesis, anti-cancer agents, including nintedanib, have been successfully applied in the treatment of patients with IPF while an oncologic approach with a cocktail of several pleiotropic anti-fibrotic agents is currently in the therapeutic pipeline of IPF. Nevertheless, epidemiologic association between IPF and lung cancer does not prove causality. Currently there is significant lack of knowledge supporting a direct association between lung fibrosis and cancer reflecting to disappointing therapeutic algorithms. An optimal therapeutic strategy for patients with both IPF and lung cancer represents an amenable need. This review article synthesizes the current state of knowledge regarding pathogenetic commonalities between IPF and lung cancer and focuses on clinical and therapeutic data that involve both disease entities.

The Lung Reporting and Data System (LU-RADS): A Proposal for Computed Tomography Screening

Despite the positive outcome of the recent randomized trial of computed tomography (CT) screening for lung cancer, substantial implementation challenges remain, including the clear reporting of relative risk and suggested workup of screen-detected nodules. Based on current literature, we propose a 6-level Lung-Reporting and Data System (LU-RADS) that classifies screening CTs by the nodule with the highest malignancy risk. As the LU-RADS level increases, the risk of malignancy increases. The LU-RADS level is linked directly to suggested follow-up pathways. Compared with current narrative reporting, this structure should improve communication with patients and clinicians, and provide a data collection framework to facilitate screening program evaluation and radiologist training. In overview, category 1 includes CTs with no nodules and returns the subject to routine screening. Category 2 scans harbor minimal risk, including <5 mm, perifissural, or long-term stable nodules that require no further workup before the next routine screening CT. Category 3 scans contain indeterminate nodules and require CT follow up with the interval dependent on nodule size (small [5-9 mm] or large [≥10 mm] and possibly transient). Category 4 scans are suspicious and are subdivided into 4A, low risk of malignancy; 4B, likely low-grade adenocarcinoma; and 4C, likely malignant. The 4B and 4C nodules have a high likelihood of neoplasm simply based on screening CT features, even if positron emission tomography, needle biopsy, and/or bronchoscopy are negative. Category 5 nodules demonstrate frankly malignant behavior on screening CT, and category 6 scans contain tissue-proven malignancies.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Investigation of lung nodule detectability in low-dose 320-slice computed tomography

Low-dose imaging protocols in chest CT are important in the screening and surveillance of suspicious and indeterminate lung nodules. Techniques that maintain nodule detectability yet permit dose reduction, particularly for large body habitus, were investigated. The objective of this study was to determine the extent to which radiation dose can be minimized while maintaining diagnostic performance through knowledgeable selection of reconstruction techniques. A 320-slice volumetric CT scanner (Aquilion ONE, Toshiba Medical Systems) was used to scan an anthropomorphic phantom at doses ranging from approximately 0.1 mGy up to that typical of low-dose CT (LDCT, approximately 5 mGy) and diagnostic CT (approximately 10 mGy). Radiation dose was measured via Farmer chamber and MOSFET dosimetry. The phantom presented simulated nodules of varying size and contrast within a heterogeneous background, and chest thickness was varied through addition of tissue-equivalent bolus about the chest. Detectability of a small solid lung nodule (3.2 mm diameter, -37 HU, typically the smallest nodule of clinical significance in screening and surveillance) was evaluated as a function of dose, patient size, reconstruction filter, and slice thickness by means of nine-alternative forced-choice (9AFC) observer tests to quantify nodule detectability. For a given reconstruction filter, nodule detectability decreased sharply below a threshold dose level due to increased image noise, especially for large body size. However, nodule detectability could be maintained at lower doses through knowledgeable selection of (smoother) reconstruction filters. For large body habitus, optimal filter selection reduced the dose required for nodule detection by up to a factor of approximately 3 (from approximately 3.3 mGy for sharp filters to approximately 1.0 mGy for the optimal filter). The results indicate that radiation dose can be reduced below the current low-dose (5 mGy) and ultralow-dose (1 mGy) levels with knowledgeable selection of reconstruction parameters. Image noise, not spatial resolution, was found to be the limiting factor in detection of small lung nodules. Therefore, the use of smoother reconstruction filters may permit lower-dose protocols without trade-off in diagnostic performance.

Management of small (3-5-mm) pulmonary nodules at chest CT: global survey of thoracic radiologists

PURPOSE

To prospectively determine management strategies used by international thoracic radiologists in evaluation of small (3-5-mm) pulmonary nodules at chest computed tomography (CT).

MATERIALS AND METHODS

Institutional review board exemption was granted for this study, which included consenting participants. An electronic survey was sent to members of major thoracic radiology societies in North America, Europe, and Asia. The main part of the survey consisted of four management questions with clinical scenarios. Associations between recommendations and years of experience, location in a region endemic for granulomatous disease, country, and practice type were assessed. Univariate analysis was performed to determine differences in follow-up recommendations on the basis of patient characteristics, percentage of chest CT scans obtained at follow-up, years of experience in radiology, and professional society affiliation of respondents. Differences in categorical variables were examined by using Pearson chi(2) and Fisher exact tests.

RESULTS

Two hundred two (25%) of approximately 800 online surveys were completed. Surveys from respondents from the United States comprised 61% of completed surveys. Median experience of respondents was 11-20 years. Fifty-two percent practice in an area endemic for granulomatous disease. Only 35% of practices have a policy in place for nodule management. In scenarios in which patients had a low likelihood of malignancy, respondents' preferential recommendation was short-term CT follow-up (3-6 months) rather than intermediate-term CT follow-up (12 months) for patients older than 40 years compared with their recommendation in patients younger than 40 years, in whom recommendations for short- or intermediate-term follow-up were roughly equal. In scenarios in which patients had a high risk of malignancy, follow-up was also strongly favored instead of biopsy, with short-term follow-up more commonly advocated. Location in an area endemic for granulomatous disease and years of experience also influenced recommendations.

CONCLUSION

Globally, the most common recommendation for CT evaluation of nodules is short-term follow-up, with a tendency toward less aggressiveness in scenarios in which patients had lower risk of malignancy and increased aggressiveness in scenarios in which patients had higher risk of malignancy.

Investigating the low-dose limits of multidetector CT in lung nodule surveillance

The purpose of this study was to evaluate the factors limiting nodule detection in thoracic computed tomography (CT) and to determine whether prior knowledge of nodule size and attenuation, available from a baseline CT study, influences the minimum radiation dose at which nodule surveillance CT scans can be performed while maintaining current levels of nodule detectability. Multiple nodules varying in attenuation (-509 to + 110 HU) and diameter (1.6 to 9.5 mm) were layered in random and ordered sequences within 2 lung cylinders made of Rando lung material and suspended within a custom-built CT phantom. Multiple CT scans were performed at varying kVp (120, 100, and 80), mA (200, 150, 100, 50, 20, and 10), and beam collimation (5, 2.5, and 1.25 mm) on a four-row multidetector scanner (Lightspeed, General Electric, Milwaukee, WI) using 0.8 s gantry rotation. The corresponding range of radiation dose over which images were acquired was 0.3-26.4 mGy. Nine observers independently performed three specific tasks, namely: (1) To detect a 3.2 mm nodule of 23 HU; (2) To detect 3.2 mm nodules of varying attenuation (-509 to -154 HU); and (3) To detect nodules varying in size (1.6-9 mm) and attenuation (-509 to 110 HU). A two-alternative forced-choice test was used in order to determine the limits of nodule detection in terms of the proportion of correct responses (Pcorr, related to the area under the ROC curve) as a summary metric of observer performance. The radiation dose levels for detection of 99% of nodules in each task were as follows: Task 1 (1 mGy); Task 2 (5 mGy); and Task 3 (7 mGy). The corresponding interobserver confidence limits were 1, 5, and 10 mGy for Tasks 1, 2, and 3, respectively. There was a fivefold increase in the radiation dose required for detection of lower-density nodules (Tasks 1 to 2). Absence of prior knowledge of the nodule size and density (Task 3) corresponds to a significant increase in the minimum required radiation dose. Significant image degradation and reduction in observer performance for all tasks occur at a dose of < or = 1 mGy. It is concluded that the size and attenuation of a nodule strongly influence the radiation dose required for confident evaluation with a minimum threshold value of 1-2 mGy (minimum dose CT). A prior knowledge of nodule size and attenuation is available from the baseline CT scan and is an important consideration in minimizing the radiation exposure required for nodule detection with surveillance CT.

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.

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.

Management of an incidentally discovered pulmonary nodule

The incidental finding of a pulmonary nodule on computed tomography (CT) is becoming an increasingly frequent event. The discovery of such a nodule should evoke the possibility of a small bronchogenic carcinoma, for which excision is indicated without delay. However, invasive diagnostic procedures should be avoided in the case of a benign lesion. The objectives of this review article are: (1) to analyze the CT criteria defining benign nodules, nodules of high suspicion of malignancy and indeterminate nodules, (2) to analyze the diagnostic performances and limitations of complementary investigations requested to characterize indeterminate lung nodules, (3) to review the criteria permitting to assess the probability of malignancy of indeterminate nodules and (4) to report on the new guidelines provided by the Fleischner Society for the management of small indeterminate pulmonary nodules, according to their prior probability of malignancy.