Photodynamic therapy (PDT) is a minimally to non-invasive therapy in which a light-sensitive molecule is activated by light to locally produce highly destructive reactive oxygen species. When employed in cancer treatment, PDT can induce tumour cell death and an anti-tumour immune response. However, in the case of non-resectable perihilar cholangiocarcinoma, PDT yields promising yet unsatisfactory results. Ruud Weijer focuses on developing novel PDT strategies to treat these patients in a selective and effective manner. This involves optimising the photosensitizers used in the technology and analysing survival signaling in PDT-treated cells.