Targeted CT image screening and its effect on lung cancer detection rate

Inflammatory status and lung function predict mortality in lung cancer screening participants

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Low-dose computed tomography (LDCT) screening trials have based their risk selection algorithm on age and tobacco exposure, but never on pulmonary risk-related biomarkers. In the present study, the baseline inflammatory status, measured by C-reactive protein (CRP) level, and lung function, measured by forced expiratory volume in 1 s (FEV₁), were tested as independent predictors of all-cause mortality in LDCT-screening participants. Between 2000 and 2010, 4413 volunteers were enrolled in two LDCT-screening trials, with evaluable baseline CRP and FEV₁ values: 2037 were included in the discovery set and 2376 were included in the validation set. The effect of low FEV₁ or high CRP alone or combined was evaluated by Kaplan–Meier mortality curves and hazard ratio (HR) with 95% confidence interval (CI) by fitting Cox proportional hazards models. The overall mortality risk was significantly higher in participants with FEV₁ of up to 90% (HR: 2.13, CI: 1.43–3.17) or CRP more than 2 mg/l (HR: 3.38, CI: 1.60–3.54) and was still significant in the fully adjusted model. The cumulative 10-year probability of death was 0.03 for participants with FEV₁ of more than 90% and CRP up to 2 mg/l, 0.05 with only FEV₁ of up to 90% or CRP above 2 mg/l, and 0.12 with FEV₁ of up to 90% and CRP above 2 mg/l. This predictive performance was confirmed in the two external validation cohorts with 10-year mortality rates of 0.06, 0.12, and 0.14, and 0.03, 0.07, and 0.14, respectively. Baseline inflammatory status and lung function reduction are independent predictors of all-cause long-term mortality in LDCT-screening participants. CRP and FEV₁ could be used to select higher-risk individuals for future LDCT screening and preventive programs.

Chronic obstructive pulmonary disease and lung cancer: inter-relationships

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is a well established risk factor for lung cancer. Newer studies reveal a myriad of other mechanisms, some proven and some putative, which may contribute to their association.

RECENT FINDINGS

There is an ever-growing bundle of evidence that suggests a close association between persistent chronic inflammation and lung cancer. A few potential targets of genetic susceptibility locus for COPD and lung cancer have been suggested. Better characterization of immune dysregulation and identification of signaling pathways may assist the development of strategies to reduce risk of developing lung cancer in patients with COPD. Current lung cancer screening strategies may exclude some patients at high risk of having lung cancer. Prospective studies indicate that a screening criterion that includes variables reflecting the severity of COPD may increase the sensitivity of the screening program and reduce 'over-diagnosis bias' of indolent lung cancers. Examples of such variables include the emphysema score generated from computed tomography scans and diffusion capacity for carbon monoxide derived from lung function tests.

SUMMARY

A better understanding of the inter-relationship between lung cancer pathogenesis and COPD has been described recently. Improving lung cancer screening strategies by incorporating markers of COPD severity has recently been proposed.

Reduced Expiratory Flow Rate among Heavy Smokers Increases Lung Cancer Risk. Results from the National Lung Screening Trial-American College of Radiology Imaging Network Cohort

RATIONALE

Although epidemiological studies consistently show that chronic obstructive pulmonary disease is associated with an increased risk of lung cancer, debate exists as to whether there is a linear relationship between the severity of airflow limitation and lung cancer risk.

OBJECTIVES

We examined this in a large, prospective study of older heavy smokers from the American College of Radiology Imaging Network subcohort of the National Lung Screening Trial (ACRIN). Airflow limitation was defined by prebronchodilator spirometry subgrouped according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) grades 1-4.

METHODS

In the National Lung Screening Trial-ACRIN cohort of 18,473 screening participants, 6,436 had airflow limitation (35%) and 12,037 (65%) had no airflow limitation. From these groups, 758 lung cancer cases were prospectively identified. Participants with airflow limitation were stratified according to GOLD groups 1 (n = 1,607), 2 (n = 3,528), 3 (n = 1,083), and 4 (n = 211). Lung cancer incidence at study end (mean follow-up, 6.4 yr) was compared between the GOLD groups and those with no airflow limitation (referent group).

MEASUREMENTS AND MAIN RESULTS

Compared with those with no airflow limitation, where lung cancer incidence was 3.78/1,000 person years, incidence rates increased in a simple linear relationship: GOLD 1 (6.27/1,000 person yr); GOLD 2 (7.86/1,000 person yr); GOLD 3 (10.71/1,000 person yr); and GOLD 4 (13.25/1,000 person yr). All relationships were significant versus the reference group at a P value of 0.0001 or less.

CONCLUSIONS

In a large prospective study of high-risk cigarette smokers, we report a strong linear relationship between increasing severity of airflow limitation and risk of lung cancer.

Airflow Limitation and Histology Shift in the National Lung Screening Trial. The NLST-ACRIN Cohort Substudy

RATIONALE

Annual computed tomography (CT) is now widely recommended for lung cancer screening in the United States, although concerns remain regarding the potential harms, including those from overdiagnosis.

OBJECTIVES

To examine the effect of airflow limitation on overdiagnosis by comparing lung cancer incidence, histology, and stage shift in a subgroup of the National Lung Screening Trial (NLST).

METHODS

In an NLST subgroup (n = 18,714), screening participants were randomized to annual computed tomography (CT, n = 9,357) or chest radiograph (n = 9,357) screening and monitored for a mean of 6.1 years. After baseline prebronchodilator spirometry, to identify the presence of airflow limitation, 18,475 subjects (99%) were assigned as having chronic obstructive pulmonary disease (COPD) or no COPD. Lung cancer prevalence, incidence, histology, and stage shift were compared after stratification by COPD.

MEASUREMENTS AND MAIN RESULTS

For screening participants with spirometric COPD (n = 6,436), there was a twofold increase in lung cancer incidence (incident rate ratio, 2.15; P < 0.001) and, when compared according to screening arm, no excess lung cancers and comparable histology. Compared with chest radiography, there was also a trend favoring reduced late-stage and increased early-stage cancers in the CT arm (P = 0.054). For those with normal baseline spirometry (n = 12,039), we found an excess of lung cancers during screening in the CT arm, almost exclusively early-stage adenocarcinoma-related cancers (histology shift and overdiagnosis). After correction for these excess cancers, stage shift was marginal (P = 0.077).

CONCLUSIONS

In the CT arm of the NLST-ACRIN (American College of Radiology Imaging Network) cohort, COPD status was associated with a doubling of lung cancer incidence, no apparent overdiagnosis, and a more favorable stage shift.

Improving selection criteria for lung cancer screening. The potential role of emphysema

RATIONALE

Lung cancer (LC) screening using low-dose chest computed tomography is now recommended in several guidelines using the National Lung Screening Trial (NLST) entry criteria (age, 55-74; ≥30 pack-years; tobacco cessation within the previous 15 yr for former smokers). Concerns exist about their lack of sensitivity.

OBJECTIVES

To evaluate the performance of NLST criteria in two different LC screening studies from Europe and the United States, and to explore the effect of using emphysema as a complementary criterion.

METHODS

Participants from the Pamplona International Early Lung Action Detection Program (P-IELCAP; n = 3,061) and the Pittsburgh Lung Screening Study (PLuSS; n = 3,638) were considered. LC cumulative frequencies, incidence densities, and annual detection rates were calculated in three hypothetical cohorts, including subjects who met NLST criteria alone, those with computed tomography-detected emphysema, and those who met NLST criteria and/or had emphysema.

MEASUREMENTS AND MAIN RESULTS

Thirty-six percent and 59% of P-IELCAP and PLuSS participants, respectively, met NLST criteria. Among these, higher LC incidence densities and detection rates were observed. However, applying NLST criteria to our original cohorts would miss as many as 39% of all LC. Annual screening of subjects meeting either NLST criteria or having emphysema detected most cancers (88% and 95% of incident LC of P-IELCAP and PLuSS, respectively) despite reducing the number of screened participants by as much as 52%.

CONCLUSIONS

LC screening based solely on NLST criteria could miss a significant number of LC cases. Combining NLST criteria and emphysema to select screening candidates results in higher LC detection rates and a lower number of cancers missed.

Lung cancer in patients with chronic obstructive pulmonary disease. Development and validation of the COPD Lung Cancer Screening Score

RATIONALE

Patients with chronic obstructive pulmonary disease (COPD) are at high risk for lung cancer (LC) and represent a potential target to improve the diagnostic yield of screening programs.

OBJECTIVES

To develop a predictive score for LC risk for patients with COPD.

METHODS

The Pamplona International Early Lung Cancer Detection Program (P-IELCAP) and the Pittsburgh Lung Screening Study (PLuSS) databases were analyzed. Only patients with COPD on spirometry were included. By logistic regression we determined which factors were independently associated with LC in PLuSS and developed a COPD LC screening score (COPD-LUCSS) to be validated in P-IELCAP.

MEASUREMENTS AND MAIN RESULTS

By regression analysis, age greater than 60, body mass index less than 25 kg/m(2), pack-years history greater than 60, and emphysema presence were independently associated with LC diagnosis and integrated into the COPD-LUCSS, which ranges from 0 to 10 points. Two COPD-LUCSS risk categories were proposed: low risk (scores 0-6) and high risk (scores 7-10). In comparison with low-risk patients, in both cohorts LC risk increased 3.5-fold in the high-risk category.

CONCLUSIONS

The COPD-LUCSS is a good predictor of LC risk in patients with COPD participating in LC screening programs. Validation in two different populations adds strength to the findings.