1439PFDG PET/CT IN PATIENTS TREATED WITH NEOADJUVANT CHEMOTHERAPY FOR LOCALIZED BONE SARCOMAS

• Published in: Annals of oncology Vol. 25; no. suppl_4; p. iv503
• Main Authors: Palmerini, E., Nanni, C., Colangeli, M., Paioli, A., Fanti, S., Gambarotti, M., Picci, P., Donati, D., Ferrari, S.
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.09.2014
• ISSN: 0923-7534; 1569-8041
• DOI: 10.1093/annonc/mdu354.28

Abstract Aim: Neoadjuvant chemotherapy is the standard treatment for Osteosarcoma (OS) and Ewing sarcoma (EW). Histological response to neoadjuvant chemotherapy is an important prognostic factor for localized bone sarcomas. Aim of this study was to evaluate the relation between primary tumor FDG PET/CT uptake and histological response and prognosis. Methods: All patients treated between April 2009-November 2013 for localized EW and OS, who underwent FDG PET/CT as part of staging workout were included. Relation between primary tumor SUVmax at baseline (SUV1) and tumor response and survival were analyzed. Good response (GR) was defined as more than >90% tumor necrosis for OS patients and grade II-III Picci necrosis and/or complete disappearance of the soft tissue component on MRI in EW patients. Results: 77 patients were enrolled: 45 EW, 32 OS; 52 were male (67%); mean age was: 17 (range: 3-39). Histolgical response: 48% of patients achieved a GR overall ( 41% of OS patients and 53% of EW patients). Median SUV1 was 6.7 and mean SUV1 was 7.6 (range 0-24), in the all series. OS Mean SUV1: 9.1(range 0-24), EW mean SUV1 6.4; (range 0-17) . With a cut-off set at 6 (SUV1), the GR rate was 29% in patients with an high SUV1 (≥6) and 69% in case of low SUV1 (<6) (p=0.0004) overall: OS patients had a GR rate of 29% when the SUV1 was high, and of 64% in case of low SUV1 (p=0.055); EW patients had a GR rate of 30% with high SUV1 and 72% in case of low SUV1 (p=0.004). The 3-year event free survival (EFS) was 35% in patients with high SUV1, and 72% in patients with low SUV1 (p=0.001) overall; OS patients had a 3-year EFS of 32% when the SUV1 was high and 66% in case of low SUV1 (p=0.1); EW patients had a 3-year EFS of 37% when the SUV1 was high and 75% in case of low SUV1 (p=0.004). Conclusions: FDG PET/CT is a useful and non-invasive tool to identify patients more likely resistant to chemotherapy. If these data will be confirmed in larger series, a SUV1 level-adapted induction chemotherapy could be proposed in localized bone sarcomas. Disclosure: All authors have declared no conflicts of interest.