Recent advances in theranostic-based extracellular vesicles in cancer stem cell diagnosis and therapy

Cancer remains a leading cause of mortality worldwide, with treatment failure and disease recurrence often driven by cancer stem cells (CSCs), which constitute a resilient subpopulation within tumours characterised by self-renewal, differentiation capacity and resistance to conventional therapies. Extracellular vesicles (EVs), including exosomes and microvesicles, are secreted by CSCs and play pivotal roles in tumour progression, immune evasion and therapeutic resistance by transporting bioactive molecules such as heat shock proteins and regulatory RNAs. These vesicles reflect the molecular signature of their parent cells and offer unique opportunities for non-invasive diagnostics and targeted therapy. The theranostic paradigm, which integrates diagnostic and therapeutic functions, leverages EVs for CSC-specific biomarker detection, drug delivery and real-time monitoring of treatment response. Advances in nanotechnology and molecular engineering have enabled the functionalization of EVs with imaging agents and therapeutic payloads, increasing their specificity and efficacy in preclinical and early clinical settings. This narrative review synthesises current knowledge on CSC biology, EV biogenesis and the evolving landscape of EV-based theranostics, highlighting translational progress, technical challenges and future directions. Theranostic EVs represent a promising frontier in precision oncology, offering transformative potential for the management of CSC-driven tumorigenesis and relapse.