Low serum levels of PGE2 (<6.5) and IL-6 (<45.8) were significant predictors of longer survival in dogs with anti-PD-L1 therapy (p = 0.033 and 0.031, respectively), whereas IL-2 and IL-6 predicted tumour response to c4G12 treatment (p = 0.030 and 0.013, respectively). Here, IL6 is linked to neoplasm.