In vitro head and neck cancer models for photodynamic and photothermal therapies

Head and neck squamous cell carcinoma (HNSCC) remains a major clinical challenge because of frequent recurrence and limited long-term survival. Photodynamic therapy (PDT) and photothermal therapy (PTT) are promising light-based strategies: PDT relies on light-activated photosensitizers to generate reactive oxygen species, whereas PTT induces localized hyperthermia via photothermal agents. Despite encouraging results, both modalities are strongly influenced by tumor microenvironment (TME) features, including hypoxia, stromal barriers, heterogeneous drug penetration, and uneven light/heat distribution. This review analyzes in vitro models used to investigate PDT/PTT in HNSCC, with emphasis on their ability to reproduce tumor complexity. Compared with 2D cultures, 3D systems better recapitulate oxygen and nutrient gradients, extracellular matrix interactions, and resistance-associated phenotypes. Multicellular spheroids and co-culture models, particularly those including fibroblasts or macrophages, provide valuable insights into how stromal and immune components modulate photosensitizer uptake and therapeutic efficacy. Patient-derived explants and organoids add clinical relevance by preserving tumor heterogeneity, while emerging 3D bioprinted and microfluidic tumor-on-chip platforms offer improved control of spatial architecture, perfusion, and dynamic microenvironmental conditions. However, major limitations remain: most HNSCC models include only a limited number of cell populations, and few integrate both functional immunity and vascularization. Advancing toward multicellular, vascularized, and immunocompetent in vitro models is essential to better predict treatment response, optimize PDT/PTT combinations, and support personalized phototherapy development in HNSCC.