ABSTRACT
PURPOSE: The purpose of this research was to determine whether insulin-like growth factor (IGF) suppression, using a long-acting analogue of somatostatin (OncoLAR, octreotide pamoate long-acting release), will decrease chemotherapy resistance by eliminating an important survival signal to osteosarcoma (OSA) cells in a relevant naturally occurring cancer model. EXPERIMNETAL DESIGN: We conducted a randomized, blinded, placebo-controlled preclinical study in pet dogs with naturally occurring OSA. The study compared primary tumor necrosis and apoptosis, and survival of pet dogs receiving OncoLAR and carboplatin chemotherapy compared with dogs receiving placebo and carboplatin. RESULTS: Dogs receiving OncoLAR had suppression of serum IGF levels by approximately 43% without toxicity. No differences in primary tumor necrosis, apoptosis, tumor IGF mRNA expression, or survival were seen between the dogs receiving OncoLAR plus chemotherapy compared with OncoLAR alone. CONCLUSION: The suppression of IGF levels by the extent and/or duration achieved in the trial was not sufficient to improve chemotherapy-related antitumor effects in pet dogs with OSA.