The diagnostic performance of routinely acquired and reported computed tomography imaging in patients presenting with suspected pleural malignancy

Abstract

Objectives: Contrast-enhanced computed tomography (CT) provides essential cross-sectional imaging data in patients with suspected pleural malignancy (PM). The performance of CT in routine practice may be lower than in previously reported research. We assessed this relative to 'real-life' factors including use of early arterial-phase contrast enhancement (by CT pulmonary angiography (CTPA)) and non-specialist radiology reporting.

Materials and methods: Routinely acquired and reported CT scans in patients recruited to the DIAPHRAGM study (a prospective, multi-centre observational study of mesothelioma biomarkers) between January 2014 and April 2016 were retrospectively reviewed. CT reports were classified as malignant if they included specific terms e.g. "suspicious of malignancy", "stage M1a" and benign if others were used e.g. "indeterminate", "no cause identified". All patients followed a standard diagnostic algorithm. The diagnostic performance of CT (overall and based on the above factors) was assessed using 2×2 Contingency Tables.

Results: 30/345 (9%) eligible patients were excluded (non-contrast (n=13) or non-contiguous CT (n=4), incomplete follow-up (n=13)). 195/315 (62%) patients studied had PM; 90% were cyto-histologically confirmed. 172/315 (55%) presented as an acute admission, of whom 31/172 (18%) had CTPA. Overall, CT sensitivity was 58% (95% CI 51-65%); specificity was 80% (95% CI 72-87%). Sensitivity of CTPA (performed in 31/315 (10%)) was lower (27% (95% CI 9-53%)) than venous-phase CT (61% (95% CI 53-68%) p=0.0056). Sensitivity of specialist thoracic radiologist reporting was higher (68% (95% CI 55-79%)) than non-specialist reporting (53% (95% CI 44-62%) p=0.0488). Specificity was not significantly different.

Conclusion: The diagnostic performance of CT in routine clinical practice is insufficient to exclude or confirm PM. A benign CT report should not dissuade pleural sampling where the presence of primary or secondary pleural malignancy would alter management. Sensitivity is lower with non-thoracic radiology reporting and particularly low using CTPA.

Keywords: Computed tomography; Diagnosis; Lung cancer; Mesothelioma; Thoracic oncology.