Emerging Role of Immunomonitoring to Predict the Clinical Outcome of Patients With Malignant Pleural Mesothelioma Treated With Radical Radiation Therapy.

PURPOSE: The present study aimed at evaluating the baseline immune profile and the immunomodulating effects of radical hemithoracic radiation therapy (RT) in patients affected by malignant pleural mesothelioma (MPM) to identify potential predictive biomarkers of therapy response, toxicity development, and eligibility for further immunotherapeutic treatments. METHODS AND MATERIALS: Blood samples were collected from 55 patients with MPM, enrolled in a phase 3 trial comparing radical hemithoracic RT (interventional arm, n = 28) with local palliative RT (control arm, n = 27). Immunomonitoring was performed before RT, at the end of treatment, and 1 month after therapy, characterizing natural killer cells, B and T lymphocytes, activated CD4 and CD8 T cells, interferon-γ- and tumor necrosis factor-α-producing T helper (Th) 1 cells, regulatory T cells, and Th17 and Th22 lymphocytes, through flow cytometry. Serum levels of interleukin (IL)-6, -8, -10 and mesothelin were quantified through Enzyme-Linked Immunosorbent Assay (ELISA) assays at the same time points. Variations in the immune parameters were investigated by Friedman test and Wilcoxon signed rank post hoc test with Bonferroni correction for multiple testing, while the prognostic effect of immune biomarkers was evaluated through Kaplan-Meier method and Spearman's correlation analysis. RESULTS: Major immune variations were noticed after radical RT compared with palliative treatment, in particular an improvement in activated T cells and in interferon-γ-producing Th1 cells after RT. In the interventional arm, baseline high levels of Th22 and IL-10 and an increase in T cells were associated with an improved survival, whereas a fold increase in serum mesothelin correlated with the development of severe toxicity. An improvement of immunosuppressive regulatory T cells was observed in both arms of treatment. CONCLUSIONS: The immunomonitoring performed in patients with MPM revealed potential prognostic biomarkers for radical hemithoracic RT treatment and identified specific immune signatures induced by RT immunomodulation, which could suggest a synergistic effect with an immunotherapeutic treatment.