CELL INTELLIGENCE · 肿瘤细胞治疗研究

PURPOSE: Immune-checkpoint blockade (ICB) has demonstrated efficacy across tumor types. However, "cold" tumors characterized by low intraepithelial T-cell infiltration exhibit poor responsiveness. We investigated whether low-dose radiotherapy (LDRT) could enhance ICB efficacy in patients with multimetastatic immune-excluded solid tumors. PATIENTS AND METHODS: We conducted a multicohort phase I clinical trial (RACIN) involving 25 patients treated with escalating doses of LDRT in combination with a backbone regimen of nivolumab, ipilimumab, aspirin, or celecoxib and low-dose cyclophosphamide. The primary endpoints were safety and tolerability; secondary endpoints included disease control rate (DCR), progression-free survival, and overall survival. Exploratory endpoint analyses used paired pre- and post-LDRT tumor biopsies for single-cell profiling of the tumor microenvironment (TME). RESULTS: The combination therapy showed a manageable safety profile, with grade 3 adverse events in 12% to 21% of patients. The overall DCR was 42%, with one patient with ovarian cancer maintaining a complete response at 3 years. In responders, enhanced CD8+ tumor-infiltrating lymphocyte (TIL) functionality was associated with increased DNA damage response signatures and the presence of PD-1+CD8+ TILs at baseline. In contrast, nonresponders exhibited heightened immune regulatory innate lymphocytes such as CD8 Mucosal-Associated Invariant T (MAIT) and regulatory natural killer (NK) cells at baseline, accompanied by a lack of immunostimulatory myeloid cells in the TME and increased TIL radiosensitivity after LDRT. CONCLUSIONS: These findings suggest that LDRT combined with ICB is safe and may contribute to immunomodulatory activity in immune-excluded tumors. CD8+ TIL dynamics, DNA repair responsiveness, and TME composition may predict response and merit further validation in controlled larger studies.