EGFR and neoplasm: In stepwise multiple linear regression analysis (insignificant independent variables removed one by one) controlled for other significant covariates such as tissue thickness, 4 biologic factors (Table 2, including tumor cell density (P = 0.015), cellular EGFR expression (P = 0.002), panitumumab-IRDye800 plasma concentration (P < 0.0001), and absence of delivery barrier (P < 0.0001), were independently associated (variance inflation factor = 1.08, 1.15, 1.16, and 1.08, respectively) with local intratumoral panitumumab-IRDye800 concentration (goodness of fit, 0.62; Fig. 6).