Overcoming the barriers of the tumor: the synergy of photodynamic therapy and immunotherapy

The aim of the study was to study the effectiveness of combination of photodynamic therapy and immunotherapy in cancer treatment. Material and Methods . We searched and analyzed 843 publications available from WoS, Scopus, MedLine and RSCI databases over the past 5 years. Out of 843 articles, 60 were included in this review. Results . Preclinical and clinical data indicate the promise of combined photodynamic therapy, which is able to enhance the immune response and overcome resistance to PD-L1 inhibitors by destroying tumor vessels and improving antibody delivery. Photodynamic therapy is actively being investigated as a method of stimulating antitumor immunity, especially in combination with immunotherapy, turning “cold” tumors into “hot” ones. It promotes the growth of cytotoxic T-lymphocytes, suppresses regulatory T-lymphocytes and improves the interaction between tumor and effector cells, while disrupting regulatory mechanisms. Photodynamic therapy can also affect the expression of PD-L1/PD-1. Given the good tolerability of photodynamic therapy, its combination with immunotherapy can increase the effectiveness of treatment while minimizing the risks. Studies have shown that tumor mutation load and PD-L1 expression can predict treatment response in non-small cell lung cancer. In patients with lung adenocarcinoma with low/ moderate tumor mutation load and negative PD-L1, an improvement in overall survival was observed, which is consistent with data on the association of tumor mutation load with response to PD-L1 inhibitors. In the context of gastric cancer, the combination of photodynamic therapy with PD-L1 blockade has shown efficacy in restoring antitumor immunity by increasing the infiltration of cytotoxic T-lymphocytes and reducing the activity of regulatory T-lymphocytes. Conclusion . The combination of photodynamic therapy and immunotherapy has great potential, as photodynamic therapy destroys cancer cells and stimulates the immune response, and immunotherapy complements and enhances this effect.