Predictors of Adverse Gastrointestinal Events After Stereotactic Body Radiation Therapy for Liver Tumors.

Abstract

To identify predictors of adverse gastrointestinal (GI) events related to stereotactic body radiation therapy (SBRT) for liver tumors. We retrospectively analyzed 56 patients who underwent SBRT for liver tumors at our institution between 2016 and 2021. The α/β ratio of the GI tract (stomach, duodenum, and large intestine) was assumed to be 3 Gy in the Linear-Quadratic model (LQ model). The dose to the GI tract, that is, the biologically effective dose 3 (BED3) was converted to a 2 Gy equivalent dose (Gy2/3=2 Gy equivalent dose, α/β=3). Using this 2 Gy equivalent dose, predictors of adverse GI events of Grade 2 or higher were investigated. The median observation period was 10 months (0-40 months) and median age was 77 years (range=29-93 years). Forty-three of the 56 patients had hepatocellular carcinoma and the other 13 had metastatic liver tumors. Tumors were irradiated with 30-54 Gy/5-18 fractions of planning target volume D95% prescription (80% isodose). Eight of the 56 patients had Grade 2 or higher adverse GI events. By univariate analysis, GI D1cc, Dmax, V20, V25, V30, and V35 were all significant predictors of Grade 2 or higher adverse GI events. Among these, gastrointestinal V35 was the most significant predictor of Grade 2 or higher adverse GI events. For SBRT of liver tumors, GI V35 was the best predictor of Grade 2 or higher adverse GI events.