Since various factors may influence tumor uptake of radiolabeled antibodies—such as extravasation from tumor capillaries, diffusion and binding within the tumor interstitium, plasma clearance, internalization, and catabolism in tumor cells [18, 19], and morphological or physical barriers—specific binding to the antigen may not be the dominant factor determining cetuximab uptake level in NSCLC tumor with EGFR expression on its cell surface below a certain level. Here, EGFR is linked to neoplasm.