ESTRO 2021 Abstract Book

S381

ESTRO 2021

carcinoma (HCC) with portal invasion, although survival benefit has been clearly established. We aimed to identify oncologic benefit of LRT as compared to best supportive care (BSC), and difference of benefit according to categorized hepatic reserve using Child-Pugh class (CPC) and ALBI (Albumin-Bilirubin) grades. Materials and Methods Patients diagnosed with HCC invading portal vein and extracted in Korean Central Cancer Registration (KCCR) between 2008 to 2014 were included and classified into LRT group and BSC group. 1:1 Propensity matching was performed to reduce selection bias and effect of potential confounders. Results A total of 1,163 patients were analyzed. The LRT group was significantly younger than BSC group (p <0.001). The mean Child-Pugh score of LRT group was 6.1, which was significantly lower than 7.7 of BSC group (p <0.001). The 51.9% of LRT group had single HCC, significantly different from 39.3% of BSC group (p=0.001). Extrahepatic metastases (EHM) were less prevalent in LRT group than BSC group (23.45 vs. 31.3%, p=0.023). The 1:1 PS-matched analysis generated 222 pairs, and all clinical characteristics were comparable between PS-matched groups. Median survival of all patients, LRT, and BSC groups were 5.0, 8.0 and 2.0 months, respectively. One year overall survival rates in LRT and BSC groups were 34.2% and 16.2%, and 12.6% and 6.8% at two years, respectively (p <0.001). Multivariate analysis showed that LRT (hazard ratio 0.41, 95% CI 0.32- 0.52), age of >60 years, presence of EHM, main tumor size of ≥10cm, and CPC B or C were independent predictors for higher mortality in patients with HCC invading portal vein (all p <0.05). In subgroup analysis according to the CPC-ALBI class, the statistical differences in survival were maintained in all CPC-ALBI class (all p <0.05). Conclusion LRT demonstrated significant benefit regarding OS and CSS. The benefit is valid for CPC A as well as CPC B patients. Our result has a significance of respresenting community-level data from all administrative districts in Korea. The difference in LRT benefit accodring to subclassified hepatic reserve shuold be investigated in future studies PH-0498 Stereotactic body radiation therapy for the management of hepatocellular carcinoma I. Roquette 1 , E. Bogart 1 , T. Lacornerie 1 , M. Ningarhari 1 , M. Le Deley 1 , E. Lartigau 2 , X. Mirabel 1 , D. Pasquier 2 1 Centre Oscar Lambret, Academic Department of Radiation Oncology, Lille, France; 2 CRIStAL, Lille University, Lille, France Purpose or Objective To describe population characteristics, efficacy, safety, and to identify prognostic factors associated with efficacy and safety of all patients treated by hepatic Cyberknife stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC) in our regional comprehensive cancer care center. Materials and Methods We retrospectively analyzed the data of 335 patients with 440 HCC treated in our center between June 2007 and December 2018. Patients had received SBRT as a first-line treatment or after other local or systemic therapies. Efficacy was estimated in terms of overall survival, progression-free survival and local control. Acute and late toxicities were described according to the 5th version of CTCAE. We used a Cox model to evaluate prognostic factors of overall survival, and logistic regression models to evaluate prognostic factors of toxicity. Finally, we collected pathological results of explanted livers for patients who had undergone liver transplantation after SBRT to evaluate response to irradiation. Results Median follow-up was 70.2 months. Nearly one third of the population had received previous local treatment for the targeted HCC. The high majority of patients were treated with 45 Grays in 3 fractions. Median GTV volume was 20.3 cc (range 0.4-700.1), median CTV volume was 60.5 cc (2.5-999.4) and median PTV volume was 87.0 cc (2.6-1,067.6). Overall survival at 12, 24 and 60 months were respectively 72% (95%CI 67-77%), 45% (39-50%) and 10% (6-14%). Relapse-free survival at 12, 24 and 60 months were respectively 62% (55-67%), 28% (22-35%) and 12% (7-19%). Local control rates at 12, 24 and 60 months were respectively 97% (94-98%), 95% (91-97%) and 95% (91-97%). Half of patients experienced acute toxicity, and 39% late toxicity. No toxicity higher than grade 3 was observed. We identified Child-Pugh score B-C, high BCLC score, the existence of portal thrombosis, and a high GTV volume and higher PTV volume reported on total hepatic volume ratio as significantly associated to the risk of death. High GTV volume and high PTV volume reported on total hepatic volume ratio were significantly associated with the occurrence of acute toxicity. Low albumin levels before treatment and high GTV volumes were significantly associated with the occurrence of late toxicity. The analysis of 11 explanted livers showed 6 complete and 5 partial responses, but the existence of out-field disease in 8 patients. Conclusion SBRT is efficient for the management of hepatocellular carcinoma, with a favorable toxicity profile. Outcome is highly related to the natural evolution of underlying cirrhosis. This therapy can be considered in the same way as other local modalities such as transarterial chemoembolization and radiofrequency for unresectable HCC or as a bridge to transplantation. PH-0499 SABR as a treatment option for HCC patients: efficacy and toxicity profile R. Carlevato 1 , V. Chiofalo 1 , L. Spinelli 1 , F.R. Giglioli 2 , P. Carucci 3 , E. Rolle 3 , G. Rizza 4 , R. Faletti 5 , R. Romagnoli 4 , G.M. Saracco 3 , P. Fonio 5 , G.C. Iorio 1 , A.S. Guarneri 1 , U. Ricardi 1 1 University of Turin, Department of oncology, radiation oncology, Turin, Italy; 2 University of Turin, Department of physics, Turin, Italy; 3 University of Turin, Department of gastroenterology, Turin, Italy; 4 University of Turin, Department of liver surgery, Turin, Italy; 5 University of Turin, Department of radiology, Turin, Italy

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