SPDL1 and renal cell carcinoma: The subgroup analysis of cancer types revealed high pre-treatment sPD-L1 as a strong risk factor in the NSCLC subgroup (HR:2.08; CI:1.81–2.38, I2 = 0% p < 0.001), whereas rather heterogeneous results were observed in RCC (HR:0.67; CI:0.12–3.86, I2 = 88% p = 0.653), melanoma (HR:1.18; CI: 0.56–2.50, I2 = 74%, p = 0.668) and mixed cohorts (HR:0.96; CI:0.47–1.96, I2 = 74%, p = 0.903) (Fig. 3).