Volume 10,Issue 5
Advances in PET/CT Metabolic Imaging in Radiotherapy Combined with Immunotherapy for Non-Small Cell Lung Cancer
According to worldwide statistics, lung cancer is the leading cause of both morbidity and mortality among all forms of cancer, and the outcome of patients with non-small cell lung cancer (NSCLC) remains poor. Monotherapy with immune checkpoint inhibitors is not very effective; radiotherapy could sensitize immunity by altering the tumor microenvironment, but the optimal sequencing, dose fractionation, and identification of benefiting populations in combination therapy do not have standardized criteria yet. The 18F-FDG PET/CT enables the non-invasive evaluation of the tumor metabolic load and provides possible application value in the overall management of combination therapy, which involves four fundamental areas including preliminary patient screening and prediction of beneficial populations, targeting volume definition of radiotherapy and dose fractionation optimization and sequence choices, the initial effectiveness evaluation during treatment, and the determination of immune-related adverse reactions and their distinction from actual progression. Existing body of evidence indicates that initial metabolic tumor volume and total lesion glycolysis are related to the immune state of the tumor microenvironment, and the initial alteration of these variables during therapy correlates moderately well with prognosis. In some immune-related adverse reactions, abnormal FDG uptake may occur prior to the emergence of clinical signs; nevertheless, it is difficult to differentiate between true progression, pseudoprogression, and post-radiotherapy inflammation. However, most of the recent studies are retrospective and of small populations and do not use standardized measures of metabolic parameters, and none of them are prospective interventional studies. In general, PET/CT metabolic imaging has the potential to be used as an auxiliary decision-making tool in the course of combined therapy, but there is still a significant gap before it can become a clinically actionable decision-making tool. The urgency of methodological standardization and prospective stratified studies is now paramount.
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