Purpose: (90)Y radioembolization has emerged as a valuable therapy for intrahepatic cholangiocellular carcinomas (ICC). We aimed to evaluate the prognostic power of FDG PET/CT and that of pretherapeutic scintigraphy with (99m)Tc-labelled macroagglutinated albumin (MAA), an index of tumour vascularization.
Methods: The study group comprised 26 consecutive patients suffering from nonresectable ICC. Before treatment with radioembolization, all patients underwent MRI of the liver, as well as MAA scintigraphy, which was followed immediately by SPECT(/CT) to quantify the liver-lung shunt fraction. Using image fusion, regions of interest were drawn around the tumours and the entire liver, and the tumour-to-liver quotient was calculated. In addition, FDG PET/CT was performed at baseline and 3 months after radioembolization, and the percentage changes in peak (ΔSUV(max)) and mean (ΔSUV(mean)) FDG uptake and in metabolic tumour volume (ΔVol(2SD)) relative to baseline were calculated. Treatment response at 3 months was also assessed using contrast-enhanced MRI and CT on the basis of standard criteria.
Results: Of 23 patients in whom follow-up MRI was available, 5 (22%) showed a partial response, 15 (65%) stable disease and 3 (13%) progressive disease. The change in all FDG values significantly predicted survival by Kaplan-Meier analysis after radioembolization; ΔVol(2SD) responders had a median survival of 97 weeks versus 30 weeks in nonresponders (P = 0.02), whereas ΔSUV(max) and ΔSUV(mean) responders had a median survival of 114 weeks (responder) versus 19 weeks (nonresponder) and 69 weeks in patients with stable disease (P < 0.05). Pretherapeutic MAA scintigraphy or MRI did not predict survival, nor did the presence of extrahepatic metastases, or prior therapies. Only ΔVol(2SD) was significantly associated with survival by univariate analysis (hazard ratio 0.25; P = 0.04) and multivariate analysis (hazard ratio 0.20, P = 0.04).
Conclusion: FDG PET/CT was able to predict patient outcome after radioembolization treatment, with the change in metabolically active tumour volume at 3 months being the best independent predictor. High tumour vascularization, as indicated by MAA scintigraphy, was not a prerequisite for successful radioembolization and was even associated with a tendency towards shorter survival.