SST and neoplasm: The tissue penetration of 111In-pentetreotide itself appears poor, likely due to its small particle range, and early studies in the 1990s—at which time there were no other chelated somatostatin analogues labeled with β-emitting radionuclides [64]—demonstrated very low response rates, with reductions in tumor size seen in <10% of cases [65, 66], even at cumulative radiation doses exceeding 20 GBq, which were potentially myelosuppressive.