Minimal-activity PET/CT for efficacy control after SIRT (MAPECSI) – clinical implementation of a resource-saving, liver-focused protocol

Abstract

Abstract Aim SIRT is an established treatment option for liver malignancies. Metabolic information can provide additional knowledge about tumoral characteristics and treatment response. FDG-PET/CT was shown to be advantageous for pre-/post-SIRT evaluation. However, whole-body PET/CT is an elaborate procedure. The aim of the study was to optimize clinical efficacy assessment after SIRT with a low-dose, low-cost protocol for focused diagnostic work-up. Methods An abdomen-only minimal-activity FDG-PET/CT protocol (MA-PET) was established as an alternative for clinically indicated whole-body PET/CT scans. After administering 40 MBq of F-18-FDG one bed position was scanned for 15 minutes. Scans were acquired before (initial scan), one month after (interim scan) and three months after SIRT (follow-up scan). Metabolic tumor activity was evaluated and was compared to standard CT follow-up results. Results 50 lobar SIRT procedures in 37 patients were analysed. HCC (28), hepatic metastases (15) and CCC (7) were treated. In 18 liver lobes initial MA-PET did not show hypermetabolic lesions, 32 liver lobes underwent interim and follow-up MA-PET. All 114 MA-PET were technically feasible. Mean radiation dose was 1.9 mSv. 64 % of HCC presented low metabolism at baseline, whereas metastases and CCC were all clearly PET-positive. Majority of radiated liver tumors showed at least partial metabolic response. PET/CT results diverged from follow-up CT in 63 % of cases. Conclusion Minimal-Activity FDG-PET/CT of the liver is a feasible tool for efficacy assessment after SIRT with low financial and radiation burden. It provides additional information to morphologic imaging modalities, which can be helpful in response appraisal and treatment planning.