ESTRO 37 Abstract book

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ESTRO 37

each NTCP model were formulated. In the additional analysis, Youden's index in conjunction with the receiver operating characteristic (ROC) analysis was applied to obtain cut-off points for each independent dosimetric risk factor. External data is extracted from an independent cohort (101 pre-CPA patients) to validate our NTCP model. The validation study applied RIHT (≥2) as the only endpoint. Results RIHT grades (=0, =1, ≥2) was found to be the prognostic factors for overall survival. Twenty (23.5%) patients and 12 (14.2%) patients experienced RIHT (≥1) and RIHT (≥2), respectively. V 15 , VS 10 and pre-CP were found to be the independent risk predictors for both RIHT (≥1) and RIHT (≥2). V 15 ≤ 33.1% and VS 10 ≥416.2 mL to be the cut-off points for RIHT (≥ 1) risk stratification, and V 15 ≤ 21.5% and VS 10 ≥ 621.8 mL for RIHT (≥2) were derived from ROC analyses. Four NTCP models (Table 1) based on their own risk factors and four corresponding nomograms were generated. Our NTCP models showed good model performance (AUC, 0.83-0.89). V 15 were extracted from the external cohort and our NTCP model and its corresponding nomogram (based on V 15 plus pre-CP) showed a good prediction performance (AUC = 0.78) for RIHT (≥2) in this validation cohort.

Results With a median follow up of 27 months, 97 out of 216 patients developed locoregional recurrences. The median disease-free survival (DFS) was 64 months (95% CI 58, 7- 69, 3 months). Radiation pneumonitis (RP) was scored in 60 patients. Most lung DVH parameters correlated with this clinical endpoint. In a multivariable logistic regression analysis, the mean lung dose and the lymph node status remained significant prognostic factors for the development of RP (p<0.05). Cardiac complications were diverse; the most frequently occurring complication was pericardial effusion (PE) (69 patients). The dose to the whole heart, the pericardium and the right ventricle all correlated highly with this endpoint. In the multivariable logistic regression analysis, the V35 of the right ventricle and the N-status remained significant prognostic factors for PE (p<0.05). A Cox regression analysis was performed to inv estigate the impact of cardiopulmonary toxicity on OS. In uni variable analysis, most lung dose parameters, but hardly any cardiac dose parameter correlated with OS. In the multivariable analysis, a higher V45 of the lungs (Lung_V45) and a higher UICC stage significantly correlated with worse OS. None of the cardiac dose volume parameters remained significant. Conclusion Cardiac dose volume parameters predicted the risk on cardiac toxicity endpoints and pulmonary dose volume parameters did so on radiation pneumonitis. In this patient cohort however, pulmonary toxicity was more important for OS for which the lung_V45 was an independent predictor. These results indicate that reducing the cardiac dose at the expense of the dose to the lungs is probably not the right treatment planning strategy. PV-0104 Dosimetric Analysis of Hepatic Toxicity after Stereotactic Body Radiation Therapy R. Luo 1 , T.S. Su 2 , P. Liang 3 , T. Cheng 3 , Y. Zhou 4 , Y. Huang 4 1 University Medical Center Freiburg, Radiation Oncology, Freiburg, Germany 2 Affiliated Tumor Hospital of Guangxi Medical University, Department of Radiation Oncology, Nanning, China 3 Rui Kang Hospital- Guangxi Traditional Chinese Medical University, Cyberknife Center, Nanning, China 4 Rui Kang Hospital- Guangxi Traditional Chinese Medical University, Department of Radiation Oncology, Nanning, China Purpose or Objective To build and validate multivariate models of normal tissue complication probability (NTCP) and their corresponding nomograms for radiation-induced hepatic toxicity (RIHT) prediction after SBRT. Material and Methods Data were obtained from 85 HCC patients who participated in Phase II clinical trial of SBRT. Total dose 39-50 Gy was administered in 3-5 fractions on consecutive days. Eligibility criteria: (1) primary HCC; (2) pre-treatment Child-Pugh (pre-CP) class A or B; (3) 1 to 3 nodular HCC lesions with a total diameter < 10 cm; Exclusion criteria: (1) portal vein thrombosis and extrahepatic metastases; (2) recurrence after liver resection or transplantation. After SBRT, a progression of at least 1 or 2 points in CP score was classified as RIHT (≥1) or (≥2). Two dosimetric datasets (V x the percentage (%) of normal liver volume receiving x Gy or more; VS x , the absolute normal liver volume (mL) spared from at least x Gy) were collected and used to build NTCP models separately. NTCP models for RIHT (≥1) or (≥2) based on clinical and dosimetric parameters were developed using logistic regression with cross-validation. Nomograms for

Conclusion V 15 and VS 10

are crucial risk predictors for RIHT (≥1 and

≥2). And the cut-off points of V 15 may provide some clue s for risk stratification. Our NTCP model and nomogram based on V 15 plus pre-CP was validated by an independent cohort. NTCP models or nomograms can help clinical doctors obtain tailored constraints for each patient. It should be noted that the CP-B patients were greater susceptibility to the development of RIHT after SBRT. PV-0105 Stereotactic body radiotherapy treatment for hepatocellular carcinoma: A phase II study J. Durand-Labrunie 1 , H. Jarraya 2 , E. Boleslawski 3 , S. Cattan 4 , T. Lacornerie 5 , D. Peiffert 6 , X. Mirabel 1 1 Centre Oscar Lambret, Département de radiothérapie, Lille, France 2 Centre Oscar Lambret, Département d'imagerie médicale, Lille, France 3 Hôpital Claude Huriez- CHRU de Lille, Chirurgie digestive et transplantation, Lille, France 4 Hôpital Claude Huriez- CHRU de Lille, Maladies de l'appareil digestif, Lille, France 5 Centre Oscar Lambret, Département de physique médicale, Lille, France 6 Centre Alexis Vautrin, Département de radiothérapie, Nancy, France Purpose or Objective Liver transplantation is the standard definitive treatment for non-metastatic hepatocellular carcinoma (HCC). However, less than 5% of patients are ultimately candidates due to frequent comorbidities and graft shortage. Traditionally, radiotherapy played a limited role in the treatment of HCC due to the risk of radiation- and VS 10