ERBB2 and cancer: Spheroids formed from a variety of different cancer cell lines, using either scaffold-free or scaffold-based culture methods, were used to evaluate novel radiotracer(s) (combinations) for PCa [51–54], osteosarcoma [55], colorectal cancer [56], neuroblastoma [57], meningioma [58], melanoma [59], NETs [60] and HER2-positive cancers [61, 62].