Diagnostic test accuracy of 18F-FDG PET/CT for prediction of programmed death ligand 1 (PD-L1) expression in solid tumours: a meta-analysis

Using 18F-FDG PET/CT to predict programmed cell death ligand expression in non-small cell lung cancer via metabolic tumour heterogeneity

OBJECTIVES

The purpose of this study is to evaluate the effectiveness of using 18F-FDG PET/CT metabolic heterogeneity to assess the programmed cell death ligand (PD-L1) expression in primary tumours.

METHODS

Data from 103 non-small cell lung cancer (NSCLC) patients undergoing 18F-FDG PET/CT were collected. PD-L1 expression was verified via biopsy or surgical specimens. The coefficient of variation (COV) assessed metabolic heterogeneity of the primary tumour. ROC curves evaluated the predictive potential of metabolic metrics and defined thresholds. Logistic regression examined predictors of PD-L1 expression.

RESULTS

The study included 103 patients (mean age: 63.65 ± 9.28 years), of whom 60 were male. Sixty-four patients had positive PD-L1 expression, while 39 had negative PD-L1 expression. COV was significantly higher in the PD-L1-positive group (Z = -2.529, P = 0.011), while no significant differences were noted in other parameters between the groups (P > 0.05 for all). The optimal cut-off value was proposed as 28.9, with sensitivity and specificity of 46.9% (34.3%-59.8%) and 82.1% (66.5%-92.5%), respectively (AUC: 0.649 (0.549, 0.741)) which can more effectively identify PD-L1-negative patients. Other metabolic parameters are less effective than COV (AUC< 0.6). In addition, COV-defined metabolic heterogeneity outperformed other metabolic parameters in predicting PD-L1 expression (P = 0.049) and emerged as an independent predictor.

CONCLUSION

Metabolic heterogeneity, described by the COV of the primary lesion, is a marker for predicting PD-L1 expression in NSCLC patients. Therefore, the COV of the primary tumour may complement conventional imaging in providing immunohistochemical information before biopsy.

ADVANCES IN KNOWLEDGE

COV of the primary tumour can predict PD-L1 expression, potentially complementing conventional imaging for immunohistochemical information prior to biopsy.

The Immune Landscape of Pheochromocytoma and Paraganglioma: Current Advances and Perspectives

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors derived from neural crest cells from adrenal medullary chromaffin tissues and extra-adrenal paraganglia, respectively. Although the current treatment for PPGLs is surgery, optimal treatment options for advanced and metastatic cases have been limited. Hence, understanding the role of the immune system in PPGL tumorigenesis can provide essential knowledge for the development of better therapeutic and tumor management strategies, especially for those with advanced and metastatic PPGLs. The first part of this review outlines the fundamental principles of the immune system and tumor microenvironment, and their role in cancer immunoediting, particularly emphasizing PPGLs. We focus on how the unique pathophysiology of PPGLs, such as their high molecular, biochemical, and imaging heterogeneity and production of several oncometabolites, creates a tumor-specific microenvironment and immunologically "cold" tumors. Thereafter, we discuss recently published studies related to the reclustering of PPGLs based on their immune signature. The second part of this review discusses future perspectives in PPGL management, including immunodiagnostic and promising immunotherapeutic approaches for converting "cold" tumors into immunologically active or "hot" tumors known for their better immunotherapy response and patient outcomes. Special emphasis is placed on potent immune-related imaging strategies and immune signatures that could be used for the reclassification, prognostication, and management of these tumors to improve patient care and prognosis. Furthermore, we introduce currently available immunotherapies and their possible combinations with other available therapies as an emerging treatment for PPGLs that targets hostile tumor environments.

PET/CT molecular imaging in the era of immune-checkpoint inhibitors therapy

Cancer immunotherapy, especially immune-checkpoint inhibitors (ICIs), has paved a new way for the treatment of many types of malignancies, particularly advanced-stage cancers. Accumulating evidence suggests that as a molecular imaging modality, positron emission tomography/computed tomography (PET/CT) can play a vital role in the management of ICIs therapy by using different molecular probes and metabolic parameters. In this review, we will provide a comprehensive overview of the clinical data to support the importance of 18F-fluorodeoxyglucose PET/CT (18F-FDG PET/CT) imaging in the treatment of ICIs, including the evaluation of the tumor microenvironment, discovery of immune-related adverse events, evaluation of therapeutic efficacy, and prediction of therapeutic prognosis. We also discuss perspectives on the development direction of 18F-FDG PET/CT imaging, with a particular emphasis on possible challenges in the future. In addition, we summarize the researches on novel PET molecular probes that are expected to potentially promote the precise application of ICIs.