Caren van Roekel

297 Summary FIGURE 5. Graphical representation of the metabolic response versus absorbed dose of each individual tumor. A decrease in TLG is associated with a higher dose. The vertical dashed line indicates the cut-off value for TLG change, below which metabolic response is defined is complete response or partial response and above which response is defined as either stable disease or progressive disease. Shaded area indicates 95% CI of the regression line. Chapter 6 is the first of two dose-response studies in 166 Ho-radioembolization. In a cohort of patients with various primary tumors, the relation between dose and response was assessed. In 36 patients, metabolic response (based on changes in total lesion glycolysis (TLG) on baseline and follow-up [ 18 F]-FDG PET/CT) was determined and categorized into complete response (CR), partial response (PR), stable disease (STBD) or progressive disease (PD). The absorbed doses in the tumors were determined on the post-treatment 166 Ho-SPECT/ CT. In the analyses, it was taken into account that the majority of patients had multiple lesions. Analyses were done at both patient- and tumor-level. At both levels, a significant dose-response relationship was established. Also, patients with response (CR or PR) had a significantly longer overall survival than patients without response (median 19 months versus 7.5 months). 11