MKI67 and neoplasm: Such pathway-specific measurements can be taken simultaneously with markers of tumor cell proliferation (cyclin D1, Ki67) or tumor growth [via fludeoxyglucose (18F) measured by PET/CT] to determine first if the drug is hitting its primary target and second if the drug is mediating tumor suppression (Kelloff et al., 2005; Gainor et al., 2014).