RT Journal Article SR Electronic T1 18F-FDG MicroPET imaging to evaluate molecularly-targeted agent efficacy in genetically-engineered rhabdomyosarcoma models JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1696 OP 1696 VO 52 IS supplement 1 A1 Anu Soundararajan A1 Laura Nelon A1 Lee Ann Zarzabal A1 Joel Michalek A1 Charles Keller YR 2011 UL http://jnm.snmjournals.org/content/52/supplement_1/1696.abstract AB 1696 Objectives Rhabdomyosarcoma (RMS), alveolar (ARMS) and embryonal (ERMS) are the most common soft tissue sarcoma of childhood. We evaluated the potential of 18F-Fluorodeoxyglucose (FDG) as a marker of therapeutic response to picropodophyllin (PPP), an IGF-1R inhibitor in our conditional mouse model. Methods The genetically-engineered Myf6Cre, Pax3:Fkhr, p53 conditional mouse model of ARMS and the Pax7CreER, Ptch1, p53 conditional model of ERMS were treated with PPP (80 mg/kg) for 12 days. Control ARMS and ERMS were treated with vehicle only. 18F-FDG microPET imaging was performed at 0, 4 and 12 d post therapy. Images were analyzed and SUVmean of tumor was calculated. Tumor volume was measured using calipers. Results Outcomes are shown in Table 1. Tumor volumes of treated ARMS and ERMS mice though increased marginally on day 4, they were significantly smaller than the tumor volume increase seen in control mice. Tumor FDG uptake was significantly reduced on day 4 for treated mice compared to their baseline and to control mice on day 4. However, by day 12, the tumor volume had increased significantly compared to baseline for ARMS and ERMS mice. In contrast the tumor FDG uptake on day 12 reached values similar or exceeding levels at diagnosis, indicating rapidly evolving resistance to therapy. Conclusions 18F-FDG PET imaging may be a potential biomarker of early response for this aggressive form of sarcoma in the context of Phase 0 (micro-dosing) studies of single agents, or Phase I/II studies where chemotherapy and targeted agents are combined to more effectively slow tumor growthTable 1(*p<0.05, vs. control) (†p<0.05, vs. baseline)(#n=3)