Assessment of 18F-fluorodeoxyglucose dual-head gamma camera in asbestos lung diseases

Positron emission tomography-computed tomography (PET-CT) in suspected malignant pleural effusion. An updated systematic review and meta-analysis

The role of PET and integrated PET-CT in the diagnostic workup of suspected malignant pleural effusions is unknown. Earlier systematic reviews (published 2014 and 2015) both included pleural pathology without effusion, and reached contradictory conclusions. Five studies have been published since the latest review. This systematic review and meta-analysis aims to summarise the evidence of PET and integrated PET-CT in predicting pleural malignancy in patients suspected of having malignant pleural effusions. A meta-analysis based on a systematic literature search in Cochrane Library, Medline, EMBASE and Clinicaltrials.gov was performed. Diagnostic studies evaluating the performance of PET or PET-CT in patients with suspected malignant pleural effusion, using pleural fluid cytology or histopathology as the reference test, and presenting sufficient data for constructing a 2x2 table were included. The quality of the studies was assessed by the Quality Assessment of Diagnostic Accuracy Studies-2 score. Subgroup analyses on image modality, interpretation method and known malignancy status pre index-test application were planned. Seven studies with low risk of bias were included. The pooled ability to separate benign from malignant effusions varied with image modality, interpretation method and known malignancy status pre index-test application. In studies using PET-CT, visual/qualitative image analysis was superior to semi-quantitative with positive (LR + ) and negative likelihood ratio (LR-) of 9.9 (4.5-15.3) respectively 0.1 (0.1-0.2). There was considerable heterogeneity among studies. In conclusion, visual/qualitative image analysis of integrated PET-CT seems to add relevant information in the work-up of suspected malignant pleural effusions with LR + and LR- close to rigorous pre-set cut-offs of > 10 and < 0.1. However, the quality of evidence was low due to inter-study heterogeneity, and inability to assess meta-bias. Clinical Trial Registration: The protocol was uploaded to the PROSPERO database (CRD42020213319) on the 13th of October 2020.

Accuracy of fluorodeoxyglucose-PET imaging for differentiating benign from malignant pleural effusions: a meta-analysis

BACKGROUND

The role of fluorodeoxyglucose (FDG)-PET imaging for diagnosing malignant pleural effusions is not well defined. The aim of this study was to summarize the evidence for its use in ruling in or out the malignant origin of a pleural effusion or thickening.

METHODS

A meta-analysis was conducted of diagnostic accuracy studies published in the Cochrane Library, PubMed, and Embase (inception to June 2013) without language restrictions. Two investigators selected studies that had evaluated the performance of FDG-PET imaging in patients with pleural effusions or thickening, using pleural cytopathology or histopathology as the reference standard for malignancy. Subgroup analyses were conducted according to FDG-PET imaging interpretation (qualitative or semiquantitative), PET imaging equipment (PET vs integrated PET-CT imaging), and/or target population (known lung cancer or malignant pleural mesothelioma). Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2. We used a bivariate random-effects model for the analysis and pooling of diagnostic performance measures across studies.

RESULTS

Fourteen non-high risk of bias studies, comprising 407 patients with malignant and 232 with benign pleural conditions, met the inclusion criteria. Semiquantitative PET imaging readings had a significantly lower sensitivity for diagnosing malignant effusions than visual assessments (82% vs 91%; P = .026). The pooled test characteristics of integrated PET-CT imaging systems using semiquantitative interpretations for identifying malignant effusions were: sensitivity, 81%; specificity, 74%; positive likelihood ratio (LR), 3.22; negative LR, 0.26; and area under the curve, 0.838. Resultant data were heterogeneous, and spectrum bias should be considered when appraising FDG-PET imaging operating characteristics.

CONCLUSIONS

The moderate accuracy of PET-CT imaging using semiquantitative readings precludes its routine recommendation for discriminating malignant from benign pleural effusions.

[Follow-up of subjects occupationally exposed to asbestos: MRI and PET scans]

MRI and PET scans are not normally used for screening and follow-up of patients following occupational exposure to asbestos. These examinations usually complement the investigation of a parenchymal mass, an effusion or pleural thickening. PET and MRI have an excellent ability to define a parenchymal lesion as malignant (cancer versus rounded atelectasis) or a pleural lesion (mesothelioma versus plaque). MRI distinguishes perfectly the involvement of sub-pleural fat by bronchial carcinoma or mesothelioma. MRI, taking account of its lack of irradiation, could be regarded as suitable for potentially repeated examinations following initial screeing by CT scan. A comparative study of multidetector scanner versus MRI, including diffusion MRI could be, nevertheless, interesting. PET cannot be proposed for the follow up or for screening on account of the irradiation induced and the difficulty of access. Pleural plaques do not take up FDG. There is no specific study of asbestos related fibrosis and there is discordance between studies of other types of pulmonary fibrosis.

Clinical utility of FDG-PET and PET/CT in non-malignant thoracic disorders

There have been several endeavors made to investigate the potential role of 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography (FDG-PET) (and tracers) and PET-computed tomography imaging in various benign disorders, particularly those related to thoracic structures. These various conditions can be broadly categorized into three groups: (a) infectious diseases (mycobacterial, fungal, bacterial infection), (b) active granulomatous disease such as sarcoidosis, and (c) other non-infectious/inflammatory conditions or proliferative disorders (e.g., radiation pneumonitis, post-lung transplant lymphoproliferative disorders, occupational pleuropulmonary complications, and post-surgical conditions), all of which can demonstrate varying degrees of FDG uptake on PET scans based upon the degree of inflammatory activity. This article reviews the current state of this very important application of FDG-PET imaging.

Contribution of positron emission tomography in pleural disease

INTRODUCTION

Positron emission tomography (PET) now plays a clear role in oncology, especially in chest tumours. We discuss the value of metabolic imaging in characterising pleural pathology in the light of our own experience and review the literature.

BACKGROUND

PET is particularly useful in characterising malignant pleural pathologies and is a factor of prognosis in mesothelioma. Metabolic imaging also provides clinical information for staging lung cancer, in researching the primary tumour in metastatic pleurisy and in monitoring chronic or recurrent pleural pathologies.

CONCLUSIONS

PET should therefore be considered as a useful tool in the diagnosis of liquid or solid pleural pathologies.

In Vivo Follow-up of Rat Tumor Models with 2-Deoxy-2-[F-18]fluoro-d-glucose/Dual-Head Coincidence Gamma Camera Imaging

Before studying the impact of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) imaging with a dual-head coincidence gamma camera (DHC) for the follow-up of animal tumor models, we wanted to optimize this technique.

METHODS

Three different animal tumor models (osteosarcoma, melanoma, and breast cancer) were studied after FDG injection. Dynamic and dual time point FDG/DHC imaging were studied from one hour to five hours postinjection. In vitro tumor cell FDG uptake was assessed in eight different tumor cell lines. In one model (osteosarcoma), tumor growth, lung metastasis emergence, and survival were assessed by classical clinical follow-up and compared to FDG imaging in a control group (n = 6) and in a group treated by endostatin liposome complexes (n = 6).

RESULTS

Images obtained five hours after injection were more reliable for tumor growth follow-up than standard images (one hour). In vitro tumor cell FDG uptake confirmed in vivo imaging studies. In eight different tumor cell lines the FDG uptake was higher after five hours incubation than after one hour (p < 0.002). With FDG follow-up, we found that FDG uptake was strongly correlated with survival and that lung metastasis larger than 5 mm could be detected.

CONCLUSION

Using the optimization proposed above, DHC/FDG functional imaging seems to be a powerful tool to study rat tumor models and to help develop novel cancer therapies.