PhD ceremony Mr. X. Xie: CT biomarkers in lung cancer screening

PhD ceremony: Mr. X. Xie, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: CT biomarkers in lung cancer screening

Promotor(s): prof. M. Oudkerk

Faculty: Medical Sciences

Interest in computed tomography (CT) screening for early detection of lung cancer is increasing. Aging and smoking, risk factors for lung cancer, are also major risk factors for cardiovascular disease and chronic obstructive pulmonary disease (COPD). The screening CT also yields quantitative information on coronary calcification, expressed in a calcium score, and on emphysema and bronchial wall thickening. The focus of this thesis is the validation of these CT biomarkers. This thesis was performed within the context of the Dutch-Belgian Randomized Lung Cancer Screening Trial (Dutch acronym: NELSON).

Research shows that low-dose CT reliably detects lung nodules with diameter of at least 5 mm. Semi-automated volumetry is more accurate than manual diameter assessment. The variability in volumetry becomes small at larger nodule size. With these findings, the lung nodule management protocol in CT screening can be optimized. Secondly, increasing calcium score categories based on chest CT are associated with higher risk of cardiovascular events. A high calcium score fairly reliably indicates high cardiovascular risk; however, a zero calcium score does not exclude the presence of coronary calcification. Thirdly, CT evaluation of emphysema and peripheral airway thickness correlates with lung function test results. Also, individuals with respiratory symptoms generally have thicker walls of large bronchi on CT. These findings confirm a morphological basis of lung function and respiratory symptoms, which can be evaluated by CT. In conclusion, integrated evaluation of CT biomarkers for coronary artery disease and COPD, on top of lung cancer, may enhance the cost-effectiveness of CT screening.