LUCIS: lung cancer imaging studies

Pulmonary nodules are of high clinical importance, as they may prove to be an early manifestation of lung cancer. Pulmonary nodules are small, focal opacities that may be solitary or multiple. A solitary pulmonary nodule (SPN) is a single, small (= 30 mm in diameter) radiographic opacity. Larger opacities are called masses and are often malignant. As imaging techniques improve and more nodules are detected, the optimal management of SPNs remains unclear. Current strategies include tissue sampling or CT follow-up. The aim of this PhD was to examine current non-invasive methods used to characterise pulmonary nodules and masses in patients with suspected lung cancer and to stage NSCLC. In doing so, this PhD helps to validate the existing methods used to diagnose and stage lung cancer correctly and, hopefully, aids in the development of new methods. In the first study, 213 participants with pulmonary nodules on CT were examined with an additional HRCT. In this study, it was concluded that HRCT of a solitary pulmonary nodule, assessed using attenuation and morphological criteria is a fast, widely available and effective method for diagnosing lung cancer correctly, and especially for ruling out cancer. In the second study, 168 patients with pulmonary lesions on CT were examined with an additional F-18-FDG PET/CT. It was concluded that when used early in the work-up of the lesions, CT raised the prevalence of lung cancer in the population to the point at which further diagnostic imaging examination could be considered redundant. Standard contrast-enhanced CT seems better suited to identify patients with lung cancer than to rule out cancer. Finally, the overall diagnostic accuracy as well as the classification probabilities and predictive values of the two modalities were not significantly different. The reproducibility of the above results was substantial. In the third study, 59 patients with pulmonary nodules or masses on chest radiography were examined with an additional DCE-CT. A qualitative as well as a quantitative assessment method was examined. It was concluded that although the results of the qualitative approach were acceptable in their own right, they did not, however, add anything new when compared to standard CT. The quantitative approach gave rise to several conclusions concerning DCE-CT analysis as well as the use of DCE-CT in the diagnosis of lung cancer: First, that DCE-CT is best analysed using logarithmic scale data transformation; second, that irrespective of the ROI method applied, it was not possible to discriminate malignant and benign; and, third, that the lack of reproducibility should be addressed. These results show us that DCE-CT is currently not a clinically feasible method for analysing pulmonary lesions. This does not necessarily mean that DCE-CT should be abandoned, but it does signify the need for further development of the current DCE-CT methods. Finally, in the fourth study, 114 patients with NSCLC were examined with both a CT and with an additional F-18-FDG PET/CT. It was concluded that there was no significant difference in the overall diagnostic accuracy of the two modalities when imaging the mediastinum for staging purposes. In conclusion, although standard contrast-enhanced CT has brought us far in the characterisation of pulmonary nodules and masses, the last decade has seen a constant move away from strictly anatomical approaches to imaging, towards more functional or analytical approaches. The desire is, of course, to be able to safely distinguish between malignant and benign nodules without the need for invasive procedures.