Caren van Roekel

234 Chapter 9 The price of the anti-reflux catheter was €1500 excluding VAT and the prices of the standard microcatheters were €275-€295 excluding VAT. Patients received 166 Ho-scout in the morning, followed by 166 Ho-SPECT/CT imaging. In the absence of relevant extrahepatic deposition, patients received the therapeutic activity in the afternoon as part of a one-day protocol. Three to five days later, another 166 Ho-SPECT/CT was acquired to assess the therapeutic absorbed dose distribution. SPECT-imaging cannot be performed directly after administration, since the abundance of gamma photons invokes detector dead- time: the recorded photon produces a pulse of a certain duration during which no second pulse can be detected (17). The distribution on the post-treatment 166 Ho-SPECT/CT was the basis for the primary endpoint. SPECT/CT imaging after 166 Ho-scout and after 166 Ho-treatment was performed on a Symbia T16 system (Siemens Health Care) with a medium-energy collimator. Images were acquired on a 128x128 matrix 120 angles over a 360° non-circular orbit (30 sec/projection) with an energy window of 81 keV. Afterwards, a low- dose CT scan was fused with the SPECT images. The reconstruction of the data was done using the Utrecht Monte Carlo System software (18). After treatment, toxicity was assessed during a telephone consultation at two weeks after treatment and by physical and laboratory examination at one and three months after treatment. Adverse events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The maximum severity of each adverse event was reported. Response to treatment was assessed on PET/CT and contrast-enhanced CT three months after treatment, blinded for catheter allocation. Response analyses were based on metabolic response to treatment, based on a change in total lesion glycolysis between baseline and three months post-treatment, according to the PERCIST guidelines (19). The primary outcome of this study was the difference in tumor to non-tumor (T/N) activity concentration ratio between the right and left liver lobes, randomized between administration with an anti-reflux and a standard microcatheter. Secondary outcomes included the difference in infusion efficiency (the percentage of activity administered), absorbed doses, the predictive value of the 166 Ho-scout, the dose-response relation and survival. For the analyses, the contours of the tumors and the parenchyma were used, that were identified on the baseline [ 18 F]-FDG PET/CT. The left/right