FDG-PET for the prediction of therapy outcome in patients with high risk soft tissue sarcomas receiving high dose chemotherapy with stem cell rescue

Abstract

9562 Background: Dynamic 2-deoxy-2-[18F]fluoro-D-glucose (FDG) PET studies were used to evaluate the FDG kinetics in pts.with high risk soft tissue sarcomas receiving induction chemotherapy consisting of adriamycin and ifosfamide (AI-G) prior to peripheral blood stem cell transplantation. The treatment effect was assessed regarding prediction of therapy outcome. Methods: The ongoing evaluation includes 8 pts. with 17 lesions. 7/8 pts. were classified as grade III with lung or multiple metastases. The restaging data served as reference for the PET data. All pts. were examined initially and after the first cycle of AI-G . The dynamic series were performed over the area of the primary tumor (n=5) or the lung metastases (n=3). SUV, fractal dimension (FD), k1, k2, k3, k4 and the vessel density (VB) were retrieved from the dynamic PET studies. Furthermore, FDG influx was calculated using the rates of the two compartment model and the formula (k1 × k3)/(k2 + k3). Discriminant analysis was applied for data analysis. Results: According to RECIST criteria, 3 pts. showed progressive disease (PD), one pt.stable disease (SD), one pt. no evidence of disease (NED) and two pts. partial remission (PR). Due to the small number of pts., we dichotomized the data in pts. with NED/PR (n=3) and pts. with SD/PD (n=4). Median SUV prior therapy was 8.3 in comparison to 4.3 after one cycle AI-G. Discriminant analysis using only the data of the initial FDG study and a single parameter for input demonstrated the highest correct classification rate (CCR) for VB (73%). The CCR of k1, k2, influx and FD were lower and equal (67%). The SUV of the first study demonstrated a lower CCR of 60%. Using the kinetic data only of the second study, CCR was equal for SUV, influx and FD as single input parameters (70%). Best results were obtained for the combination of VB of the first study and either influx or FD of the second study with a CCR of 89%. Conclusions: The significance of vessel density calculated from the data of the initial PET study and the non-significance for the second PET examination indicated a major change in the angiogenesis within the initial phase of treatment. On the basis of these data prediction of chemo-sensitivity of the tumor and moreover of the therapy outcome might be possible. No significant financial relationships to disclose.