EGFR and neoplasm: sEGFR levels in A431 tumor-bearing mice were 837 ± 71 ng/mL plasma, corresponding to ∼2.5 sEGFR for each 89Zr-imgatuzumab molecule in circulation for the 10 μg tracer dose, reflecting a high degree of competition of sEGFR with tumor-bound EGFR.