Treatment of Metastatic Osteosarcoma With the Somatostatin Analog OncoLar: Significant Reduction of Insulin-Like Growth Factor-1 Serum Levels

Background Insulin-like growth factor-1 (IGF-1) has been implicated in the growth and/or metastasis of osteosarcoma (OS) and chondrosarcoma based on in vitro and experimental animal studies. Study Purpose To determine the degree of growth hormone (GH), IGF-1 axis blockade, toxicities, and antitumor effect of OncoLar (ONC) (Novartis, East Hanover, NJ, U.S.A.) in OS. Design/Methods A phase 1 study with ONC enrolled 21 OS patients (median age 19 y) in four cohorts: ONC 60 mg or 90 mg intramuscularly every 4 weeks with/without tamoxifen (TAM) 20 mg oral daily. Results There were no dose-limiting toxicities. Nineteen percent of patients had grade III drug-related toxicities including: 62% of patients showed progressive disease after two courses (8 wk). Nineteen percent received four courses. No clinical responses were observed. At weeks two and eight of therapy, IGF-1 serum levels dropped 46% (P < 0.0001, n = 21) and 53% (P = 0.003, n = 10). The difference of the area under the curve (AUC) minus baseline AUC (ΔAUC) for arginine-stimulated GH serum levels at week two was lower than baseline (P < 0.01). At weeks two and eight, GH peak values were lower than baseline (P < 0.0001 and P = 0.002, respectively). Conclusions A long-acting somatostatin analog was able to lower IGF-1 levels of OS patients. IGF-BP-3 and GH were only transiently reduced. Although ONC was well tolerated, no sustained clinical responses were observed. The pathophysiology of serum versus tissue concentrations of IGF-1 as well as the interplay of IGFs, IGF-binding proteins, and other growth factors and cytokines in osteosarcoma warrants further investigation. A better understanding of these processes should lead to a more effective exploitation of these pathways for the targeted therapy of OS.