The Caudate Lobe: The Blind Spot in Radioembolization or an Overlooked Opportunity?

Abstract

PURPOSE: The caudate lobe (CL) is impartial to the functional left and right hemi-liver and has outspoken inter-individual differences in arterial vascularization. Unfortunately, this complexity is not specifically taken into account during radioembolization treatment (RE), potentially resulting in under- or overtreatment of the CL. The objective of this study was to evaluate the CL coverage in RE and determine the detection rate of the CL arteries on CT angiography during work-up. METHODS: In all consecutive patients who underwent RE treatment between May 2012-January 2015, (99m)Tc-MAA SPECT/CT and posttreatment scans ((90)Y-bremsstrahlung SPECT/CT, (90)Y-PET/CT, or (166)Ho-SPECT/CT) were reviewed for activity in the CL. Pretreatment CT angiographies were reviewed for the visibility of the CL arteries. RESULTS: Eighty-two patients were treated. In 32/82 (39 %) the CL was involved. In 6/32 (19 %) patients, no activity was seen on the posttreatment scan in the CL, whereas in 40/50 (80 %) patients without CL tumor involvement, the CL was treated. (99m)Tc-MAA SPECT/CT and final posttreatment scans were discordant in 16/78 (21 %). (99m)Tc-MAA SPECT/CT had a positive and negative predictive value of 94 % and 46 %, respectively, for activity in the CL after RE. In untreated CLs, significant hypertrophy was observed with a median volume increase of 33 % (p = 0.02). CL arteries were seldom visible on the pretreatment CT; the identification rate was 12-17 %. CONCLUSION: Currently in RE treatments, targeting or sparing of the CL is highly erratic and independent of tumor involvement. Intentional treatment or bypassing of the CL seems worthwhile to either improve tumor coverage or enhance the functional liver remnant.