Therapeutic Use of Tolvaptan in Cancer-Related Hyponatremia: Benefits, Risks, and Clinical Guidance

Abstract

Positron Emission Tomography–Computed Tomography (PET/CT) has become integral to modern oncology, offering combined functional-metabolic and anatomical information. Recent technological advances – including digital PET detectors, highperformance time-of-flight (TOF) systems, and hybrid PET/MRI platforms – have markedly enhanced PET image quality and quantification. Concurrently, novel PET radiotracers beyond standard ^18F-FDG (fluorodeoxyglucose) are emerging, targeting specific tumor features: for example, PSMA ligands for prostate cancer, FAPI ligands for fibroblast-rich tumors, somatostatin analogues (DOTATATE) for neuroendocrine tumors, FLT for proliferation, and amino-acid probes for brain and prostate cancers. These tracers often detect lesions that FDG misses. Quantitative PET biomarkers have advanced from simple SUVs (standardized uptake values) to volumetric measures (metabolic tumor volume, total lesion glycolysis) and high-dimensional radiomic features. Artificial intelligence (AI) and deep-learning tools now enable automated tumor segmentation, noise reduction, and prognostic modeling from PET images. Clinically, extensive evidence shows PET/CT improves staging and response assessment in major cancers. For example, PSMA PET/CT detects bone metastases in prostate cancer with ~98% sensitivity versus ~85% for traditional bone scintigraphy, and FDG PET/CT upstages breast and lung cancers in a significant fraction of cases. Compared to conventional imaging (CT, MRI, bone scan), PET/CT often demonstrates higher sensitivity and comparable specificity for nodal and distant metastases. PET/MRI may further improve lesion detection in selected cancers while reducing radiation dose. Workflow improvements from total-body PET and AI can accelerate scans and reduce dose. Cost-effectiveness studies suggest PET/CT can be economically justified by avoiding unnecessary biopsies or treatments, although access and reimbursement vary. Radiation dose and tracer safety remain important; FDA approvals exist for many tracers (e.g. ^68Ga-PSMA-11, ^18F-DCFPyL, ^68Ga-DOTATATE) while novel agents (e.g. FAPI) are investigational. This comprehensive review synthesizes recent literature and guidelines (SNMMI, EANM, NCCN) to provide an updated analysis of PET/CT innovations in oncology. It details technical advances, new tracers, quantitative imaging, and clinical evidence across major tumor types, compares PET/CT to other modalities, and discusses economic and regulatory considerations.