Caren van Roekel

244 Chapter 9 Exploratory sub-analysis of impact of anti-reflux catheter in right hepatic artery only The anti-reflux catheter was deployed in the right hepatic artery in twelve patients (per protocol analysis). The median T/N activity concentration ratio with the anti-reflux catheter was 4.0 (range 0.9-8.7) versus 3.8 with the standard microcatheter (range 0.8-9.0) (difference in median +0.2, 95%CI -1.11 – 2.32, p=0.42). Safety Grade ≥3 laboratory toxicity was present in three patients (14%), and four patients (19%) experienced grade ≥3 clinical toxicity. Two deaths occurred within three months after treatment: one patient died of disease progression (5%), the other of radioembolization-induced liver disease (5%) (Table S2. Median overall survival was 7.8 months (95%CI 6.4-12.9). Agreement between 166 Ho-scout and 166 Ho-therapy The agreement between the dose distribution on 166 Ho-scout and 166 Ho-therapy was calculated for 17 patients. Four patients were excluded from the analysis, for the following reasons: treatment simulation by 99m Tc-MAA (n=1; 166 Ho-scout was not available due to a production failure and treatment simulation was performed using 99m Tc-MAA), no post-treatment 166 Ho-SPECT/CT performed (n=1), stasis during treatment (defined as retrograde flow into adjacent arteries) (n=1), and 166 Ho-scout activity for the left hepatic territory abusively administered in the right hepatic artery (n=1). Using the anti-reflux catheter led to a substantially worse agreement for estimating the tumor-absorbed dose with 166 Ho-scout (95% limits of agreement -58 Gy and +49 Gy) than when using the standard microcatheter (95% limits of agreement -27 Gy and +29 Gy) (Figure S2a,b). The agreement for estimating the parenchymal dose was similar between both catheter types (95% limits of agreement -3 Gy and +2 Gy for the anti-reflux catheter and -3 Gy and +3 Gy for the standard microcatheter) (Figure S2c,d). DISCUSSION Colorectal cancer liver metastases are challenging to treat with radioembolization. These tumors are often diffusely metastasized throughout