Per cent emphysema is associated with respiratory and lung cancer mortality in the general population: a cohort study

High-Attenuation Areas on Chest Computed Tomography and Clinical Respiratory Outcomes in Community-Dwelling Adults

RATIONALE

Areas of increased lung attenuation visualized by computed tomography are associated with all-cause mortality in the general population. It is uncertain whether this association is attributable to interstitial lung disease (ILD).

OBJECTIVES

To determine whether high-attenuation areas are associated with the risk of ILD hospitalization and mortality in the general population.

METHODS

We performed a cohort study of 6,808 adults aged 45-84 years sampled from six communities in the United States. High-attenuation areas were defined as the percentage of imaged lung volume with attenuation values between -600 and -250 Hounsfield units. An adjudication panel determined ILD hospitalization and death.

MEASUREMENTS AND MAIN RESULTS

After adjudication, 52 participants had a diagnosis of ILD during 75,232 person-years (median, 12.2 yr) of follow-up. There were 48 hospitalizations attributable to ILD (crude rate, 6.4 per 10,000 person-years). Twenty participants died as a result of ILD (crude rate, 2.7 per 10,000 person-years). High-attenuation areas were associated with an increased rate of ILD hospitalization (adjusted hazard ratio, 2.6 per 1-SD increment in high-attenuation areas; 95% confidence interval, 1.9-3.5; P < 0.001), a finding that was stronger among men, African Americans, and Hispanics. High-attenuation areas were also associated with an increased rate of ILD-specific death (adjusted hazard ratio, 2.3; 95% confidence interval, 1.7-3.0; P < 0.001). Our findings were consistent among both smokers and nonsmokers.

CONCLUSIONS

Areas of increased lung attenuation are a novel risk factor for ILD hospitalization and mortality. Measurement of high-attenuation areas by screening and diagnostic computed tomography may be warranted in at-risk adults.

Is mitochondrial dysfunction a driving mechanism linking COPD to nonsmall cell lung carcinoma?

Chronic obstructive pulmonary disease (COPD) patients are at increased risk of developing nonsmall cell lung carcinoma, irrespective of their smoking history. Although the mechanisms behind this observation are not clear, established drivers of carcinogenesis in COPD include oxidative stress and sustained chronic inflammation. Mitochondria are critical in these two processes and recent evidence links increased oxidative stress in COPD patients to mitochondrial damage. We therefore postulate that mitochondrial damage in COPD patients leads to increased oxidative stress and chronic inflammation, thereby increasing the risk of carcinogenesis.

The functional state of the mitochondrion is dependent on the balance between its biogenesis and degradation (mitophagy). Dysfunctional mitochondria are a source of oxidative stress and inflammasome activation. In COPD, there is impaired translocation of the ubiquitin-related degradation molecule Parkin following activation of the Pink1 mitophagy pathway, resulting in excessive dysfunctional mitochondria. We hypothesise that deranged pathways in mitochondrial biogenesis and mitophagy in COPD can account for the increased risk in carcinogenesis. To test this hypothesis, animal models exposed to cigarette smoke and developing emphysema and lung cancer should be developed. In the future, the use of mitochondria-based antioxidants should be studied as an adjunct with the aim of reducing the risk of COPD-associated cancer.

Lung cancer and chronic obstructive pulmonary disease: From a clinical perspective

Chronic obstructive pulmonary disease (COPD) and lung cancer are devastating pulmonary diseases that commonly coexist and present a number of clinical challenges. COPD confers a higher risk for lung cancer development, but available chemopreventive measures remain rudimentary. Current studies have shown a marked benefit of cancer screening in the COPD population, although challenges remain, including the common underdiagnosis of COPD. COPD-associated lung cancer presents distinct clinical features. Treatment for lung cancer coexisting with COPD is challenging as COPD may increase postoperative morbidities and decrease survival. In this review, we outline current progress in the understanding of the clinical association between COPD and lung cancer, and suggest possible cancer prevention strategies in this patient population.

Chronic obstructive pulmonary disease and risk of lung cancer: a meta-analysis of prospective cohort studies

Background

Studies exploring the association between chronic obstructive pulmonary disease (COPD) and lung cancer have yielded mixed results. We conducted a meta-analysis of the published prospective cohort studies to have a clear understanding about this association.

Methods

We searched the MEDLINE and EMBASE databases from inception to December 31, 2016. Bibliographies were also reviewed for additional information. Random-effects model was used to calculate summary relative risk (SRR) and corresponding 95% confidence interval (CI).

Results

Eighteen prospective cohort studies were part of this meta-analysis, involving 12,442 lung cancer cases with a median duration of follow- up of 5 years (range: 1.5-20 years). A history of COPD, emphysema or chronic bronchitis conferred SRRs of 2.06 (95% CIs: 1.50-2.85; n=14 studies), 2.33 (95% CIs: 1.56-3.49; n=4 studies) and 1.17 (95%CIs: 0.79-1.73; n=3 studies), respectively. Stratification by COPD severity yielded SRR of 1.46 (95% CIs: 1.20-1.76) for mild, 2.05 (95% CIs: 1.67-2.52) for moderate and 2.44(95% CIs: 1.73-3.45) for severe COPD, respectively. There were similar risk estimations for never and ever smokers. The SRR was statistically higher for squamous cell cancer than that for adenocarcinoma and for small cell cancer of the lung (P<0.05).

Conclusion

This meta-analysis indicated a significantly increased risk of lung cancer for COPD, emphysema, but not for chronic bronchitis. For the prevention of lung cancer, it is of importance for early detection of COPD in lung cancer surveillance.

Incidence of non-pulmonary cancer and lung cancer by amount of emphysema and airway wall thickness: a community-based cohort

There is limited knowledge about the prognostic value of quantitative computed tomography (CT) measures of emphysema and airway wall thickness in cancer.The aim of this study was to investigate if using CT to quantitatively assess the amount of emphysema and airway wall thickness independently predicts the subsequent incidence of non-pulmonary cancer and lung cancer.In the GenKOLS study of 2003-2005, 947 ever-smokers performed spirometry and underwent CT examination. The main predictors were the amount of emphysema measured by the percentage of low attenuation areas (%LAA) on CT and standardised measures of airway wall thickness (AWT-PI10). Cancer data from 2003-2013 were obtained from the Norwegian Cancer Register. The hazard ratio associated with emphysema and airway wall thickness was assessed using Cox proportional hazards regression for cancer diagnoses.During 10 years of follow-up, non-pulmonary cancer was diagnosed in 11% of the subjects with LAA <3%, in 19% of subjects with LAA 3-10%, and in 17% of subjects with LAA ≥10%. Corresponding numbers for lung cancer were 2%, 3% and 11%, respectively. After adjustment, the baseline amount of emphysema remained a significant predictor of the incidence of non-pulmonary cancer and lung cancer. Airway wall thickness did not predict cancer independently.This study offers a strong argument that emphysema is an independent risk factor for both non-pulmonary cancer and lung cancer.

Regional Emphysema Score Predicting Overall Survival, Quality of Life, and Pulmonary Function Recovery in Early-Stage Lung Cancer Patients

INTRODUCTION

Pulmonary emphysema is a frequent comorbidity in lung cancer, but its role in tumor prognosis remains obscure. Our aim was to evaluate the impact of the regional emphysema score (RES) on a patient's overall survival, quality of life (QOL), and recovery of pulmonary function in stage I to II lung cancer.

METHODS

Between 1997 and 2009, a total of 1073 patients were identified and divided into two surgical groups-cancer in the emphysematous (group 1 [n = 565]) and nonemphysematous (group 2 [n = 435]) regions-and one nonsurgical group (group 3 [n = 73]). RES was derived from the emphysematous region and categorized as mild (≤5%), moderate (6%-24%), or severe (25%-60%).

RESULTS

In group 1, patients with a moderate or severe RES experienced slight decreases in postoperative forced expiratory volume in 1 second, but increases in the ratio of forced expiratory volume in 1 second to forced vital capacity compared with those with a mild RES (p < 0.01); however, this correlation was not observed in group 2. Posttreatment QOL was lower in patients with higher RESs in all groups, mainly owing to dyspnea (p < 0.05). Cox regression analysis revealed that patients with a higher RES had significantly poorer survival in both surgical groups, with adjusted hazard ratios of 1.41 and 1.43 for a moderate RES and 1.63 and 2.04 for a severe RES, respectively; however, this association was insignificant in the nonsurgical group (adjusted hazard ratio of 0.99 for a moderate or severe RES).

CONCLUSIONS

In surgically treated patients with cancer in the emphysematous region, RES is associated with postoperative changes in lung function. RES is also predictive of posttreatment QOL related to dyspnea in early-stage lung cancer. In both surgical groups, RES is an independent predictor of survival.