ESTRO 2020 Abstract Book

S551 ESTRO 2020

and the median interval between end of RT and surgery was 6.7 weeks. At resection, all patients had evidence of pathological tumour regression (TRG2 = 2; TRG3 = 2). Both patients with TRG2 had distant relapses at 5 months and 12 months after surgery, respectively with no locoregional recurrence observed. CD8 + cytotoxic T-cells (median pre- CRT: 83.6 cells/mm 2 vs. post-CRT: 5.3 cells/mm 2 ), FOXP3 + regulatory T-cell (median 108.9 vs. 12.3), CD3 + T-cells (median 185.9 vs. 80.2) and CD68 + macrophages (median 135.0 vs. 36.1) decreased after CRT in all patients. Similarly, the combined immune and tumour cell PD-L1 expression decreased after CRT (median 79.8 vs. 23.0) in all patients. However, tumour cell only PD-L1 expression increased significantly from 86.2 to 421.6 cells/mm 2 in the patient who recurred at 5 months with distant metastases. The CD8 + /FOXP3 + T-cell ratio was also increased in both patients who had distant relapses (pre-CRT vs. post-CRT: 0.53 vs. 0.85 and 2.01 vs. 3.45) ( Figure 1 ).

was graded according to the Common Terminology Criteria for Adverse Events v4.03. Results Between 2010 und 2017 a total of 194 lesions were treated (74 patients with HCC, 47 patients with CCC and 73 patients with liver metastases). Nine patients (4,6 %) with primary liver cancer (CCC=6, HCC=3) developed grade 3 toxicities without progression (Bilirubin increase n=6, gGT increase n=1, cholangitis n=3). Only the D800cc (HR 1.043, 95% CI 1.009-1,077, p=0.012), as well as higher doses to the PV 15cc (HR 1,030, p=0.025) the PV5 mean (HR 1,019 p=0,024), the PV5 25cc (HR 1,020, p=0,013) the PV5 35cc (HR 1,024, p=0,048) and the the PV5 45cc (HR 1,023, p=0,031) correlated with the presence of central hepatobiliary toxicities. Neither the pre-treatment Child Pugh score, nor the ALBI grade, or the presence of biliary stents correlated the incidence of toxicities. Conclusion A higher D800cc as well as a higher dose to the PV 15cc and to the PV5 mean, PV5 25cc and PV5 35cc were associated with a higher risk of hepatobiliary toxicities, only in patients with primary liver cancer. A 5 mm expansion from the PV (PV5) proved to be an appropriate surrogate. PO-1036 Analysis of serum pancreatic exocrine enzyme after radiotherapy for pancreatic carcinoma T. Iwai 1 , K. Ogura 1 , M. Yamashita 2 , T. Ogata 1 , T. Hattori 1 , T. Mitsuyoshi 1 , T. Imagumbai 1 , M. Kokubo 1 1 Kobe City Medical Center General Hospital, Radiation Oncology, Kobe, Japan ; 2 Kobe City Medical Center General Hospital, Radiological Technology, Kobe, Japan Purpose or Objective Serum pancreatic exocrine enzyme deficiency is concerned with pancreatic exocrine insufficiency, which cause malnutrition. There are few studies of pancreatic exocrine enzyme in patients with pancreatic carcinoma after radiotherapy (RT). The aim of this study is to analyze serum pancreatic enzyme levels and evaluate the association between the levels and the irradiated dose to pancreas. Material and Methods Between April 2006 and November 2017, pancreatic carcinoma patients without distant metastasis treated with definitive RT in our hospital were evaluated. Serum amylase (AMY) levels within 30 days before RT and 90 days after RT were collected. We defined ‘AMY deficiency’ as the decline to the levels of less than normal lower limit and also less than half of itself before RT. Then, we used the Kaplan-Meier method to estimate the time to AMY deficiency after RT (defined as ‘AMY deficiency free probability’) and conducted univariate analysis to compare groups using log-rank test with sex, age, performance status (PS) score [Eastern Cooperative Oncology Group (ECOG)], cancer stage [Union for International Cancer Control (UICC) 7 th ], tumor location, tumor diameter, CA19- 9 level before RT, and dose volume index (mean pancreatic dose and the normal pancreas volume that received 30 Gy (V30Gy), 40 Gy (V40Gy), 45Gy (V45Gy) and 50 Gy (V50Gy)). Results Among the 35 pancreatic carcinoma patients treated with definitive RT, 23 patients were included in this study. There were 11 male and 12 female, with a median age of 66 (range, 38-86) years. 20 patients had a PS score of 0 or 1, 3 patients had a PS score of 2. One was diagnosed with clinical stage IB disease, 1 with clinical stage IIA disease, 3 with clinical stage IIB disease, 18 with clinical stage IIIB disease. 13 tumors were located in the head or uncus of pancreas and 10 tumors were located body or tail of pancreas. The median tumor diameter was 30 mm (range, 20-100 mm), and the median CA19-9 levels before RT was 216 U/mL (range, 1.2-26751 U/mL). The median prescription dose was 50.4 Gy (range, 45-64.8 Gy/15-36 fr), and the median V30Gy, V40Gy, V45Gy, V50Gy, mean dose of normal pancreas were 36.8%, 62.0%, 69.3%, 78.0%,

Conclusion As expected, concurrent CRT decreases intratumoral immune cells in oesophageal cancer. However, increase in tumour cell PD-L1 expression and CD8 + /FOXP3 + T-cell ratio appeared to be associated with distant relapse in this preliminary analysis. In contrast, standard pathological evaluation such as TRG did not predict for disease relapse. The negative prognostic impact of higher CD8 + /FOXP3 + ratio may represent a greater proportion of exhausted or non-viable cytotoxic T-cells after CRT. The addition of anti-PD1/PD-L1 therapy may have a role in this setting. This study is on-going and additional analysis will be performed once recruitment is completed to confirm these early findings. PO-1035 Central hepatobiliary toxicity after liver SBRT and hypo-fractionated Radiotherapy E. Gkika 1 , C. Weis 1 , S. Kirste 1 , F. Mohammad 1 , S. Adebahr 1 , D. Baltas 1 , T. Brunner 2 , A.L. Grosu 1 1 Uniklinik Freiburg, Radiation Oncology, Freiburg, Germany ; 2 Uniklinik Magdeburg, Radiation Oncology, Magdeburg, Germany Purpose or Objective Aim of the study was to analyse the centrally hepatobiliary toxicity after liver stereotactic body radiotherapy (SBRT) and hypo-fractionated radiotherapy. Material and Methods Patients with cholangiocarcinoma (CCC) or hepatocellular carcinoma (HCC) or liver metastasis (M) were treated with SBRT or hypo-fractionated RT in 3-12 fractions. Doses to the liver and liver hilum were converted to a 2 Gy – equieffective dose (EQD2) with an α/β von 2.5 and 3 respectively. The liver hilum was defined by an isotropic expansion of 5mm (PV5), 10mm (PV10) and15mm (PV15) from the portal vein (PV), from the splenic confluence to the first bifurcation of the left and right portal veins. Afterwards we evaluated the mean and the maximum dose and the dose to 5cc, 15cc, 25cc, 35cc, 45cc for PV, PV5, PV10 and PV15. Furthermore, we evaluated the median dose to the liver (LDmean) and the dose to 700cc(D700cc) and 800cc(D800cc) of normal liver. Hepatobiliary toxicity