Photodynamic therapy can change the tumor immune microenvironment and improve the prognosis of patients with advanced colorectal cancer

Photodynamic therapy (PDT) has shown potential in the treatment of various cancers. We conducted a retrospective analysis was conducted on 119 patients diagnosed with stage III-IV colorectal cancer at Lanzhou University Second Hospital between November 2020 and November 2023. The results showed that the overall survival (OS) of the PDT group was significantly longer than that of the non-PDT group (p=0.005). Two months after PDT treatment, the objective response rate (ORR) was 43.9%, and the disease control rate (DCR) was 88.5%. A marked increase in the local infiltration of various immune cells, including CD3+ T cells, CD4+ T cells, CD8+ T cells, and macrophages, was observed in the tumor tissue. No severe PDT-related adverse events were noted. In conclusion, PDT is an effective treatment for advanced colorectal cancer with no significant adverse reactions. PDT may enhance the effects of immunotherapy by recruiting immune cells into the tumor microenvironment.