EGFR and neoplasm: We suggest instead that this serial dual Affibody-based tracer imaging technique, possibly in tandem with tracers such as 11C-labeled erlotinib [43] that target the EGFR tyrosine kinase domain (and therefore estimate the receptors in both the membrane and cytoplasm), could provide non-invasive methods for studying changes in numbers and locations of receptors during tumor growth and EGFR cycling.