Abstract PS1-06-17: A retrospective analysis of capecitabine-induced imaging hepatic steatosis in metastatic breast cancer: prevalence and resolution

Abstract Background: Capecitabine is a valid monotherapy option in multiple metastatic breast cancer (mBC) subtypes. While case reports of capecitabine-related hepatic steatosis have been published, its prevalence remains unknown. Traditional monitoring relies primarily on biochemical tests, which may not fully capture hepatic changes. Our aim was to evaluate the prevalence of capecitabine-related hepatic steatosis and determine whether routinely performed [18F]FDG PET/CT could quantify hepatic changes during capecitabine treatment, including in patients without visually evident steatosis. Methods: We conducted a retrospective analysis of patients with mBC treated with capecitabine between 2014 and 2021 at Gustave Roussy. Clinico-biological variables (age, BMI, metastatic sites, therapy line, dihydropyrimidine dehydrogenase (DPD) testing, biochemical liver tests) at baseline were collected. Baseline PET/CT, first evaluation (= 4th line (23%). When available, DPD testing revealed partial deficit in 16/138 patients (12%). Median treatment duration was 298 days (range 80-2162). Sequential imaging analysis was available for 122 patients with both baseline and first evaluation PET/CT scans, and 77 patients at capecitabine discontinuation. No patients showed hepatic steatosis at baseline. At first evaluation, hepatic steatosis was observed in 3/122 patients (2.5%). All 3 patients with steatosis underwent dose reduction due to other capecitabine toxicities (hand-foot syndrome in 2 patients, general condition deterioration requiring weight-based dose adjustment in 1 patient), resulting in resolution of CT steatosis in 2 patients. At final PET/CT, steatosis was present in 4/77 patients (5.2%) and resolved in 3 patients on follow-up imaging after changing treatment line. All patients who developed visible steatosis received capecitabine monotherapy. Quantitative analysis revealed small magnitude hepatic changes during capecitabine treatment: mean HU liver decreased by -2.3 units (95%CI -4.0 to -0.6, p=0.007) and SUVmean liver increased by +0.2 units (95% CI +0.1 to +0.2, p