Streamlining Radioembolization for CCC and Metastatic Liver Cancer

TARE uses radioactive microspheres (20-60 μm), which are trapped in tumors due to abnormal vasculature, while normal liver sinusoids (≤15 μm) prevent their passage. However, some microspheres may drain into hepatic veins and reach the lungs, risking radiation pneumonitis. Pre-procedural evaluation with angiography and nuclear imaging (MAA scan with SPECT/CT) is required to calculate lung shunt fraction (LSF). TARE is contraindicated if LSF \>20%, and may be used with caution if LSF is 10-20%.

Findings associated with high LSF include large tumors, hepatic vein invasion, TIPS, and dysmorphic intratumoral vessels. In contrast, small or medium sized (\<7 cm) cholangiocarcinoma or metastatic liver cancers without hepatic vein invasion or dysmorphic vessels show consistently low LSF (\<5%). Over 10 years at SNUH, no cases of radiation pneumonitis have been observed in such patients. Therefore, "streamlining TARE" omits pre-procedural nuclear imaging for this group to reduce procedural delays, reserving nuclear imaging for patients who need it most.

SIR-Spheres (SIRTEX) facilitate single-session TARE as they are provided in a bulk vial, unlike TheraSphere which requires advance preparation based on dosimetry.

Protocol Overview :

Procedure: Same-day angiography, cone-beam CT, and TARE using SIR-Spheres.

Dosimetry: Lung shunt fraction is assumed as 5%, estimated lung dose is capped at 10 Gy.

Tumor dose goal: 80\~400 Gy (around 250Gy)(single-compartment MIRD), or 300 \~ 1000 Gy (multi-compartment MIRD). minimal tumor dose by partition dosimetry : 100Gy

Software: Simplicit90Y for planning, Y90 PET/CT the next day for post-treatment dosimetry.

Follow-up: 1 year; additional treatments follow institutional guidelines.

This streamlined approach maximizes efficiency while maintaining safety in selected patients.