FOLR2 and neoplasm: Our in vitro binding assay of 68Ga-FOL with CHO-FR-β+ and CHO-FR-β− cells revealed specificity and high affinity for FR-β (5.1 ± 1.1 nM), close to the binding affinity of 18F-FOL (1.0 nM) for FR-positive tumor xenografts reported earlier14.