IMRT-induced acute hepatic toxicity and analysis of the dose-volume effects in gastric cancer patients treated with postoperative radiation.

e15542 Background: To investigate the postoperative-IMRT-induced hepatic toxicity in gastric cancer, and analyze the correlations between liver dose-volumetric parameters and acute hepatic toxicity, so as to give a dose-limitation suggestion for postoperative-IMRT in gastric cancer patients. Methods: Between June 2013 and June 2016, 67 patients with gastric cancer treated with post-operative adjuvant IMRT were reviewed. Prescribed dose was from 45Gy to 54Gy, in a daily fraction of 1.8–2.0 Gy. Dose constraints included: liver V30 < 40%, liver V40 < 30%, a mean dose of two kidneys < 18Gy and one kidney V6 < 50% if a mean dose of another kidney is more than 18Gy or another kidney has been resected. The following clinical and dose-volumetric parameters were examined: age, gender, concurrent chemotherapy, chemotherapy cycles before IMRT, chemotherapy cycles after IMRT, total chemotherapy cycles, Dmean (mean dose to liver), V5, V10, V15, V20, V25, V30, V35, and V40. Acute hepatic toxicity was evaluated between 1 and 4 months after radiation, according to the Common Terminology Criteria for Adverse Events(CTCAE), version 3.0. Results: 46 patients developed grade 1 hepatic toxicity, and 8 patients developed grade 2 hepatic toxicity after radiation, while there was no grade 3 or more severe hepatic toxicity. On univariate analysis, chemotherapy cycles after radiation, total chemotherapy cycles, Dmean, V20, V25, V30, V35 and V40 show correlations with Grade 2 acute hepatic toxicity (p = 0.009, 0.004, 0.015, 0.040, 0.005, 0.001, 0.001, 0.001, respectively). On multivariate analyses, V40 was the only significant parameter correlated with the risk of Grade 2 acute hepatic toxicity (P = 0.002). Using ROC curves, we find that to avoid grade 2 acute hepatic injury, the dose-volumetric limitations would be: Dmean of 22.4Gy, V20 of 42.3%, V25 of 38%, V30 of 27%, V35 of 17%, and V40 of 13%. Conclusions: IMRT is safe for gastric cancer treated with postoperative-radiotherapy as to liver. The grade 2 acute hepatic toxicity could be avoided by restricting dose-volumetric parameters of liver.