BACKGROUND: Immune checkpoint blockade (ICB) therapy, including antibodies targeting the programmed cell death protein 1 (PD-1) pathway, has significantly prolonged the overall survival (OS) in patients with advanced cervical cancer (CC). ICB treatment affects both target cells and various components released by immune cells, which can be observed in peripheral blood. However, there has been limited research on the dynamics of peripheral blood immunophenotyping and its association with OS in CC patients receiving ICB therapy. METHODS: Patients with persistent, recurrent, or metastatic CC treated with ICB were enrolled between December 2019 and September 2022. The dynamic changes in peripheral blood immune cells, immunoglobulins, and complement components were analyzed at baseline (within 30 days prior to the first ICB cycle) and after the second cycle of ICB treatment (4-6 weeks after the first ICB treatment). Associations of the baseline levels of peripheral blood immune cells, immunoglobulins, complement components with OS were analyzed using multivariable Cox regression analysis. RESULTS: In this retrospective cohort study, 119 patients who received at least two cycles of ICB were included. Data on peripheral blood immune cells, immunoglobulins, and complement components were available for 70 of these patients. The percentages of suppressor T (Ts) cells and natural killer (NK) cells in peripheral blood increased significantly post-ICB treatment, whereas the Th/Ts ratio and IgM levels decreased. The percentages of cytotoxic T (Tc) cells, Ts cells, the Th/Ts ratio, and levels of IgM, IgA, C3, and C4 were significantly associated with the OS of patients. Furthermore, multivariable Cox regression analysis found that a high level of IgA was associated with poor OS of the patients (HR = 2.918
95% CI, 1.081-7.877, P = 0.035). CONCLUSION: Our study demonstrated the potential proliferation of peripheral blood anti-tumor T cells in some CC patients undergoing ICB therapy. The observed associations between peripheral blood immunophenotyping and OS suggest that these biomarkers might have potential as prognostic tools.