Tumor-to-muscle ratios were even higher for the here tested compounds than those that were reported for other anti-PD-L1 PET probes (34 and 28 for our labeled Nbs, compared to only 2–10 for the mAb, 12 for the Adnectin, and 9 for the Nb109) adding to the potential of our compounds. This evidence concerns the gene CD274 and neoplasm.