In 2019, Fässler et al showed in this journal that the presence of tumor-associated antibodies correlated with response to immune checkpoint inhibitor treatment in patients with metastatic melanoma. The results of this study suggested that tumor-associated antibodies directed against melanocyte-differentiation antigens and the cancer-germline antigen NY-ESO-1 should be further investigated as candidate biomarkers for response to immune checkpoint inhibitors. The aim of the current study was to validate and extend these previous findings. Therefore, we examined the correlation between serum levels of tumor-associated antibodies and tumor response after treatment with immune checkpoint inhibitors in patients with metastatic melanoma.
All patients included in this prospective study were diagnosed with advanced stage melanoma and treated with nivolumab or pembrolizumab monotherapy. Blood samples were collected before and during treatment. Serum levels of tumor-associated antibodies against the melanocyte differentiation antigen Melan-A and the cancer germline antigens NY-ESO-1, MAGE-C2, MAGE-A6 and ROPN1B were measured at baseline and during treatment. Differences between responders and non-responders were assessed using the Mann-Whitney U-test, and differences between different overall survival categories with the Kruskal-Wallis test. P values ≤0.05 were considered significant.
Serum samples of 58 patients with advanced melanoma with long-term follow-up (>3 years) were collected. In contrast to the findings of Fässler et al, for all antibodies tested, we found no significant differences between serum levels of responders and non-responders before or during treatment with immune checkpoint inhibitors. In addition, no significant differences were found in serum levels of tumor-associated antibodies for different overall survival groups.
Although our study included a larger and more mature cohort of patients with longer follow-up, we could not externally validate the findings of Fässler et al. In addition, we were not able to identify other cancer germline antigens as predictive biomarkers of response to immune checkpoint inhibitors in patients advanced melanoma. Based on the results of the present study, clinical applicability of tumor-associated antibodies directed against tumor antigens as predictive biomarkers for immune checkpoint inhibitors in patients with advanced melanoma is not feasible.