Analysis of metabolic liver function and MR-morphological cholestatic parameters after SBRT of liver metastases

This study examined the longitudinal changes in metabolic liver function and MR-morphological dilatation of intrahepatic bile ducts in patients with stereotactic body radiation therapy (SBRT) for liver metastases. This retrospective study included 64 patients with SBRT of 84 liver metastases between February 2005 and January 2019. To evaluate hepatobiliary toxicity, the laboratory parameters albumin, alanine-transaminase (ALAT), aspartate-transaminase (ASAT), bilirubin and gamma-glutamyltransferase (GGT) and the qualitative dilatation of MR-morphological peritumoural, intrahepatic bile ducts were analyzed from pre- up to 12 months post-SBRT. The liver metastases were irradiated with a median D50 to the GTV of BEDα/β=10 Gy = 134 Gy (range 51–219 Gy) resulting in a median mean dose Dmean-L-EQD2α/β=3 Gy = 11.8 Gy (range 0.4–65.6 Gy) to the total liver. The central hepatobiliary tract (cHBT) was exposed to a median Dmean-cHBT-BEDα/β=10 Gy = 8.3 Gy (range 0.1–81.6 Gy). Significant decreases in albumin and increases in GGT and bilirubin were observed up to 12 months post-SBRT. Dmean-L-EQD2α/β=3 Gy, Dmean-cHBT-BEDα/β=10 Gy and VBEDα/β=10Gy66Gy-cHBT and VBEDα/β=10Gy72Gy-cHBT were significant cofactors influencing the course of GGT, ASAT and bilirubin, but not for albumin and ALAT. MR-morphological, short- and long-term dilatation of peritumoural bile ducts were associated with significant higher VBEDα/β=10Gy66Gy-cHBT and VBEDα/β=10Gy72Gy-cHBT values and were significantly more frequent for SBRT of target volumes with < 3 cm distance to the cHBT. SBRT of liver metastases was associated with minor alterations in metabolic liver function. High dose exposure and proximity of the liver metastases to the cHBT may lead to locoregional bile duct dilatation after SBRT. Further evaluation of metabolic and MR-morphological changes in liver function is recommended in personalised oncological treatment approaches for liver-directed therapies.