Solitary Pulmonary Nodules: Impact of Quantitative Contrast-enhanced CT on the Cost-effectiveness of FDG-PET
Introduction
Evaluation of the solitary pulmonary nodule (SPN) remains a substantial and costly challenge in modern medicine. It is therefore desirable to develop strategies for the evaluation of SPNs that are cost-effective and reduce unnecessary biopsy or thoracotomy. 2-Fluoro-2-d-[(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) has been shown to be cost-effective for the evaluation of SPNs in the USA [1], Europe [2], Japan [3] and Australia [4]. More recently, novel diagnostic computed tomography (CT) techniques that quantify contrast enhancement, have been proposed as an alternative method for characterization of SPNs, but their cost-effectiveness is unknown.
Quantitative contrast-enhanced CT (QECT) can be used to describe techniques that measure the changes in attenuation resulting from administration of contrast medium during a series of conventional CT images acquired over time. Some techniques use simple measures such as peak enhancement value or maximal enhancement rate, whilst others use mathematical modelling to determine absolute values of physiological parameters including tissue perfusion, relative blood volume and capillary permeability. As patterns of contrast enhancement are determined by the status of the vascular system, QECT can be used to capture physiological parameters reflecting the vasculature within tumours and other tissues [5]. Indeed, peak CT enhancement of lung and renal cancer has been shown to correlate with histological measurements of microvessel density 6, 7, 8.
A range of QECT techniques have been used to characterize pulmonary mass lesions 7, 9, 10, 11, 12. The largest study has been a multi-centre trial that used peak enhancement values to characterize SPNs in 356 patients [9]. In this multi-centre trial it was reported that the absence of significant lung nodule enhancement (≤15 HU) at CT was strongly predictive of benignity highlighting the potential clinical value of QECT in the evaluation of indeterminate solitary pulmonary nodules.
The aims of this study were to compare the cost-effectiveness of QECT and FDG-PET and to determine whether the cost-effectiveness of FDG-PET could be enhanced by the addition of QECT into FDG-PET based strategies for the management of SPNs.
Section snippets
Decision Tree Sensitivity Analysis
A recognized approach to evaluating the cost-effectiveness of diagnostic imaging techniques which has emerged in the diagnostic imaging literature involves theoretical modelling of the decision making process called “decision tree analysis” 13, 14. A decision tree can be described as a horizontal flow chart that depicts all the choices, events and outcomes that stem from an initial choice for a defined problem. Sensitivity analysis is used to test the assumptions used in the model by varying
Results
At the baseline prevalence of malignancy (54%), the QECT strategy incurs the least cost ($5560/patient) followed by the QECT+FDG-PET strategy ($5910/patient) then the FDG-PET strategy $6027/patient (Table 1). The CT strategy alone incurs the most cost at $6065/patient because, in this strategy, a greater number of patients undergo biopsy and/or surgery.
The most cost-effective strategy at a prevalence of 54% is the QECT+FDG-PET strategy (ICAR $12059.18/patient), followed by the FDG-PET strategy
Discussion
The decision tree analysis indicates that adopting QECT with an incremental cost of 27.5% above conventional CT, is likely to improve the cost-effectiveness of strategies for the management of SPNs. In terms of cost-effectiveness, QECT is always preferred to CT alone in the investigation of solitary pulmonary nodules. QECT with FDG-PET is more cost-effective than FDG-PET with conventional CT except at high disease prevalence levels where their cost-effectiveness is approximately equal. In
Acknowledgements
The authors thank Wesley Research Institute for assistance with funding.
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