Effect of balloon-occlusion microcatheters on tumor targeting in holmium-166 radioembolization: a within-patient comparative study

Abstract: Balloon occlusion microcatheters (BOC) have been proposed to improve tumor targeting during transarterial radioembolization (TARE), but supporting data remain limited. In this exploratory, within-patient study, seven patients undergoing holmium-166 ( 166 Ho) TARE received paired 166 Ho-scout injections via a conventional end-hole catheter (CEHC) and a BOC at identical arterial positions. Tumor-to-normal liver uptake ratio (TNR) was quantified on SPECT/CT, and liver perfusion territories (LPT) were assessed on cone-beam CT. BOC was associated with lower TNRs in six of seven patients (geometric mean ratio 0.41; p = 0.06, not significant) and frequently with reduced LPTs (7–60%) and incomplete tumor coverage. In one patient, higher TNR with BOC coincided with reduced tumor coverage. These findings suggest variable effects of BOC on tumor targeting in 166 Ho-scout work-up and warrant further investigation. Level of evidence: Level 3; prospective within-patient comparative study.