ESTRO 2020 Abstract Book

S175 ESTRO 2020

restaging CT-scan after FOLFIRINOX was finished prior to SBRT. Patients were followed with CT scans to consider potential resectability. Patients received 8 cycles of FOLFIRINOX followed by SBRT (5 fractions of 8Gy) if no tumor progression after the FOLFIRINOX treatment was observed. Following SBRT, resection was considered in case tumor downstaging was seen on restaging CT scans. Results Fifty patients were included and did start with FOLFIRINOX treatment. Thirty-nine (78%) patients were not progressive under chemotherapy and were treated with SBRT. The 3-years overall survival and the median OS for patients who had finished SBRT was 13% and 17 months (95% CI 14-21) and was 7 months (95% CI 6-8) in patients who had not received SBRT (p<0.001). Six (12%) patients underwent exploratory laparotomy, all resulting in a complete (R0) resection. Two patients had a complete pathological response. The median OS for the six patients that underwent resection was 23 months (95% CI 13-34). Two (5%) grade 3 or 4 adverse events after SBRT were observed. Two (5%) grade 5 adverse events consisting of gastro-intestinal bleeding within three months after SBRT were observed. Conclusion FOLFIRINOX followed by SBRT in patients with LAPC shows excellent antitumor activity with a 3-years overall survival of 13%. In 6 (12%) patients a potentially curative resection could be pursued following this combined treatment, with a complete histological response being observed in two patients. OC-0332 Recurrence patterns and outcomes of dose escalation SBRT for pancreatic cancer: A multicenter study OC-0333 Long-term outcomes of radical radiotherapy with a simultaneous integrated boost in esophageal cancer T. Luo 1 , J. Chen 1,2 , H. Guo 1 , T. Zhai 1 , R. Huang 1 , Z. Chen 3 , K. Lin 4 , C. Zeng 1 , W. Liu 1 , M. Zhou 1 , D. Li 1 , D. Li 1 , C. Chen 1 1 Cancer Hospital of Shantou University Medical College, Department of Radiation Oncology, Shantou City, China ; 2 CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology- University of Oxford, Oxford, United Kingdom ; 3 The University of Hongkong - Shenzhen Hospital, Department of Oncology, Shenzhen City, China ; 4 Shantou University Medical College, Department of Public Health and Preventive Medicine, Shantou City, China Purpose or Objective Conventionally fractionated radiotherapy with a total dose of 50-60 Gy in combination with concurrent chemotherapy is the standard nonsurgical treatment for patients with esophageal cancer. However, more than 50% of these patients eventually experienced disease progression at locoregional sites. Thus, local tumor control remains an unmet clinical need for EC. To address this challenge, we launched a phase II, single arm clinical trial to evaluate the tolerability and efficacy of simultaneous integrated boost (SIB) radiotherapy with concurrent chemotherapy in esophageal squamous cell carcinoma (ESCC). Here, we report the long-term results of this study. Material and Methods Between 2012 and 2015, a total number of 87 patients with primary ESCC were enrolled in this trial. The majority Presentation cancelled

(92.0%) of these patients had locoregionally advanced disease. Seventeen (19.5%) patients had positive supracavicular lymph nodes. All patients were subjected to definite chemoradiotherapy. Radiotherapy was delivered using the simultaneous integrated boost approach. The prescribed dose was 66 Gy to the gross tumor and at the same time 54Gy to the subclinical disease in 30 fractions given over 6 weeks. Patients were also treated with 2 cycles of concurrent chemotherapy on weeks 1 and week 5, and another 2 cycles of adjuvant chemotherapy at week 8 and 11. The chemotherapy regimen consisted of cisplatin, 75 mg/m 2 , intravenous on day 1 and fluorouracil, 0.5 g/m 2 , intravenous on day 1 to 4. The end points of this study include acute and late toxicities, 1-, 3- and 5-year locoregional tumor control rates and overall survivals. Results The majority of patients enrolled in this trial completed radiotherapy and concurrent chemotherapy. The most common ≥ grade 3 acute toxicities were neutropenia (13.8%), thrombopenia (4.6%), esophagitis (4.6%) and vomiting (4.6%). The median follow-up time was 52 months (2-83) for all patients and 68 months (19- 83) for those still alive. There were 16 cases (18.4%) of severe late toxicities, including 4 cases (4.6%) of Grade 5 and 7 cases (8.0%) of Grade 3 esophageal ulceration, 3 cases (3.4%) of Grade 3 esophageal stricture and 2 cases (2.3%) of Grade 3 radiation-induced pneumonia. Twenty- four (27.6%) patients had locoregional disease progression. The majority (81.3%) of locally recurrent lesions were within the dose-escalation region in the initial radiation plan, while most recurrent lymph nodes were found out- of-field (84.6%) and in the supraclavicular region (69.2%). The 1-, 3- and 5-year locoregional tumor control and overall survival rates were 78.0%, 72.4% and 72.4%, 82.8%, 60.8% and 58.3%. Conclusion Concurrent chemotherapy with radiation SIB appears to be well tolerated in patients with ESCC. Patients exhibited improved local tumor control and survival compared to historical data. Phase III trial comparing SIB with standard- dose radiotherapy delivered by conventional fractionation in ESCC is ongoing. OC-0334 pCR versus 2 years DFS:an update analysis of a pooled dataset of 5492 locally advanced rectal cancer G. Chiloiro 1 , C. Masciocchi 1 , J. Van Soest 2 , K. Bujko 3 , L. Collette 4 , M.A. Gambacorta 1 , J. Gerard 5 , R. Glynne- Jones 6 , S.Y. Ngan 7 , C. Rödel 8 , A. Sainato 9 , A. Damiani 1 , A. Dekker 2 , V. Valentini 1 1 Fondazione Policlinico Universitario “A. Gemelli” IRCCS, Radiation Oncology, Rome, Italy ; 2 GROW School for Oncology and Developmental Biology- Maastricht University, Radiation Oncology, Maastricht, The Netherlands ; 3 Maria Skłodowska-Curie Memorial Cancer Centre, Radiotherapy, Warsaw, Poland ; 4 EORTC Headquarters, Statistics, Brussels, Belgium ; 5 Centre Antoine Lacassagne- Nice Côte-d'Azur University, Radiation Oncology, Nice, France ; 6 Mount Vernon Centre for Cancer Treatment-, Radiation Oncology, Northwood, United Kingdom ; 7 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia ; 8 University Hospital Frankfurt- Goethe University, Radiotherapy and Oncology, Frankfurt-, Germany ; 9 Pisa University Hospital, Radiation Oncology, Pisa, Italy