Dose-volumetric parameters predicting radiation-induced hepatic toxicity in unresectable hepatocellular carcinoma patients treated with three-dimensional conformal radiotherapy

Purpose: To identify the dose-volumetric parameters associated with the risk of radiation-induced hepatic toxicity (RIHT) in hepatocellular carcinoma patients treated with three-dimensional conformal radiotherapy. Methods and Materials: A total of 105 hepatocellular carcinoma patients underwent three-dimensional conformal radiotherapy (total dose range, 44-58.5 Gy; median, 54). RIHT was scored within 4 months of completing three-dimensional conformal radiotherapy. The dose-volume parameters analyzed were the gross tumor volume; normal liver volume; total liver volume; radiation dose; mean dose to the normal liver; percentage of the normal liver volume receiving ≥20, ≥25, ≥30, ≥35, and ≥40 Gy; percentage of the total liver volume receiving ≥20, ≥25, ≥30, ≥35, and ≥40 Gy; and the normal tissue complication probability. Results: Of the 105 patients, Grade 1 RIHT was observed in 21 (20.0%), Grade 2 in 7 (6.7%), Grade 3 in 5 (4.8%), and Grade 4 in 1 (1.0%) patient. No fatal Grade 5 RIHT developed. On multivariate analysis for predicting Grade 2 or worse RIHT, the total liver volume receiving ≥30 Gy was the only significant parameter (p < 0.001). Grade 2 or worse RIHT was observed in only 2 (2.4%) of 85 patients with a total liver volume receiving 30 Gy of ≤60% and in 11 (55.0%) of 20 patients with >60% (p < 0.001). Conclusion: The total liver volume receiving ≥30 Gy appears to be a useful dose-volumetric parameter for predicting the risk of RIHT. This volume should be limited to ≤60% whenever possible to minimize the risk of Grade 2 or worse RIHT.