EUD based 90Y-TOF-PET post selective internal radionuclide therapy provides a similar TCP in HCC than observed in EBRT

Abstract Background: Tumor equivalent uniform dose (EUD) is a predictor of patient outcome after selective internal radionuclide therapy (SIRT) of hepatocellular carcinoma (HCC) and can be evaluated with 90Y-TOF-PET. The aim is to evaluate the correlation between PET based tumors EUD and the clinical response evaluated with dual molecular tracer (11C-acetate and 18F-FDG) PET/CT post SIRT. Methods: 34 HCC tumors in 22 patients were prospectively evaluated. The metabolic response was characterized by the Total Lesion Metabolism variation (ΔTLM) between baseline and follow up. This response allowed to compute a Tumor Control Probability (TCP) as a function of the tumor EUD. Results: The dose response correlation was exponential-asymptotic shaped and highly significant (R=0.72, P < 0.001). With a cutoff of 40Gy, the metabolic response was strongly different in both groups (median response 35% versus 100%, p< 0.001). Moreover, the TCP (EUD) was very similar to that observed in External Beam Radiation Therapy (EBRT). Conclusions: EUD based 90Y TOF-PET/CT predicts the metabolic response after SIRT of HCC assessed using dual molecular PET tracers and provides a similar TCP curve to that observed in EBRT. Both TCPs show that a EUD of 100 Gy is needed and sufficient to control a HCC.