Increase of lymphocytes and eosinophils, and decrease of neutrophils at an early stage of anti-PD-1 antibody treatment is a favorable sign for advanced malignant melanoma.

The advent of immune checkpoint inhibitors such as anti-PD-1 antibodies had a striking impact on the treatment for advanced malignant melanoma. However, less than half of the patients benefited from those antibodies, and biomarkers that could sensitively differentiate responders from non-responders are urgently needed. Herein, we explored such biomarkers by retrospectively analyzing clinical data from patients with advanced malignant melanoma treated with nivolumab and pembrolizumab. We found that anti-PD-1 antibody was especially effective for those with metastasis only to soft tissues. Although no significant difference was found in the baseline value of relative neutrophil count (RNC), relative lymphocyte count (RLC), neutrophil to lymphocyte ratio (NLR), and relative eosinophil count (REC) between responders and non-responders, responders after anti-PD-1 therapy revealed the increase of lymphocytes and eosinophils and the decrease of neutrophils within the first 6 weeks of the treatment. We also calculated the change of RNC and RLC 3 weeks and 6 weeks after the initiation of the therapy and designated as NΔ3-LΔ3 and NΔ6-LΔ6 respectively. NΔ3-LΔ3 was significantly decreased in responders, which suggest that the neutrophil decrease and lymphocyte increase after as early as 3 weeks of anti-PD-1 therapy might be a useful clinical indicator. In addition, the difference of NΔ6-LΔ6 between responders and non-responders was even more robust. These data suggest that change of RNC, RLC, and REC together with the combination of NΔ3-LΔ3 and NΔ6-LΔ6 might be a useful tool for early and sensitive biomarkers for anti-PD-1 therapy.