Characterization and dynamics of the soluble immunological microenvironment in melanoma patients undergoing radiotherapy

BACKGROUND AND PURPOSE: Malignant melanoma constitutes an aggressive tumor of the skin, the pathogenesis of which is influenced by immunological processes. In this context, the influence of radiotherapy (RT) on inflammatory markers has not been studied in detail, yet.

MATERIALS AND METHODS: In this prospective analysis, 28 patients were recruited, 24 of these could be included for further analysis. According to protocol, patients underwent three blood-draws: before, after half of RT-fractions and after completion of RT. Serum levels of programmed death-ligand (PD-L) 1 and 2, interleukin 6 and cytotoxic t-lymphocyte-associated protein 4 were assessed via enzyme-linked immunosorbent assay and compared to healthy volunteers. Correlation with clinical data was attempted.

RESULTS: Comparing patients with healthy volunteers, a significant difference in the mean baseline serum-level of PD-L1 (90.1 pg/ml vs. 76.7 pg/ml for patients vs. control, respectively; p = 0.024) and PD-L2 (4.4 ng/ml vs. 8.7 ng/ml; p = 0.04) could be found. Increased levels of PD-L1 were only found in patients with prior immunotherapy. There was a tendency for higher interleukin 6 levels in the patients (8.5 pg/ml vs. 0.6 pg/ml; p = 0.052). No significant differences in serum levels could be found between the three time points.

CONCLUSION: The present study reveals a characteristic immunological pattern for melanoma patients in comparison to healthy controls. Future studies will have to focus on a putative correlation between immunological markers and clinical outcome parameters.