Caren van Roekel

140 Chapter 5 classification. Firth’s logistic regression was used to explore associations between baseline characteristics and mode of progression. This type of analysis was chosen to correct for small-sample bias (38). The analysis for the association between extrahepatic disease at baseline and disease progression was adjusted for the following possible confounders: time from diagnosis of metastases to treatment, primary tumor in situ, KRAS mutation vs wild type, number of lines of previous systemic treatment (one versus two or more). The analysis for the association between type of microsphere used and disease progression was adjusted for the following possible confounders: age, time from diagnosis of metastases to treatment, primary tumor in situ, KRAS mutation vs wild type, number of lines of previous systemic treatment (one versus two or more) and presence of extrahepatic disease. Univariable survival analysis by the Kaplan-Meier method was used to estimate median overall survival (OS) in all treated patients. A Cox proportional hazards model with Firth’s correction was used to test for differences in survival between patients with and without extrahepatic disease at baseline. All analyses were performed using R version 3.6.2 for Windows. We report effect estimates with associated 95%CIs and corresponding two-sided p-values. RESULTS Patient demographics Of the total cohort of 129 treated patients in our institution, 39 patients (30%) did not have three-month follow-up imaging available because of the following reasons: follow-up imaging in other hospital (n=5), only follow-up imaging at one month post-treatment (n=21), only response evaluation using 18 F-FDG PET (with no accompanying contrast-enhanced CT) (n=5), clinical progression (n=5), no follow-up imaging available (n=2) and RFA artefacts (n=1). The remaining 90 patients had either CT (n=67, 74%) or MRI (n=23, 26%) images available at baseline and three-months follow-up. Median interval between baseline imaging and radioembolization was 18 days (range 1 – 46), between radioembolization and follow-up 91 days (range 62 – 165). Baseline- and treatment characteristics are summarized in Table 1. 166 Ho-microspheres, glass 90 Y-microspheres, and resin 90 Y-microspheres were used in 24 (27%), 20 (22%), and 46 patients (51%) respectively. None of the patients received systemic treatment before (<4 weeks), during or after (<3 months) radioembolization.