Feasibility of Radioembolization With Yttrium-90 Resin Microspheres Without Lung Shunt Fraction Measurement for...

To evaluate the feasibility of streamlined radioembolization using yttrium-90 resin microspheres without lung shunt fraction (LSF) assessment in patients with intrahepatic cholangiocarcinoma (ICC).

This single-center retrospective study included 23 patients with ICC who underwent radioembolization using resin microspheres (SIR-Spheres; SIRTEX, Woburn, MA, USA) without LSF measurement between April 2022 and April 2025. Eligibility criteria, based on prior institutional data, included a target tumor size less than 10 cm, absence of hepatic vein invasion and intratumoral dysmorphic vessels, and an institutional waiting time exceeding one week for macroaggregated albumin scintigraphy. All patients had at least one follow-up imaging study. Radiation activity was prescribed according to tumor location, liver function, and clinical setting, using both single-compartment and multi-compartment dosimetry under the assumptions of a 5% LSF and a tumor-to-normal (TN) ratio of 3. Post-treatment yttrium-90 PET/CT dosimetry was performed in 12 patients. Treatment-related toxicity, tumor response, and local tumor progression-free survival were analyzed.

The median administered activity was 1.43 GBq (interquartile range, 0.89-2.15). The median mean absorbed dose to the perfused tissue was 147 Gy, and the median tumor absorbed dose (TAD) was 339 Gy, assuming a TN ratio of 3. Post-treatment PET/CT analysis demonstrated a median TAD of 371 Gy and a median TN ratio of 4.7. No patient developed symptomatic radiation pneumonitis. Best tumor response was partial response in 52% of patients and stable disease in 48%. Local tumor progression-free survival rates at six months, one year, and two years were 95.2%, 81.1%, and 81.1%, respectively.

Streamlined radioembolization without LSF assessment appears feasible and may represent a practical alternative to conventional multi-step workflows in patients with ICC measuring less than 10 cm.