ESTRO 2020 Abstract book

S189 ESTRO 2020

OC-0332 Recurrence patterns and outcomes of dose escalation SBRT for pancreatic cancer: A multicenter study X. Zhu 1 , C. Yangsen 1 , S. Tingshi 2 , Y. Yusheng 1 , Z. Xixu 3 , J. Xiaoping 1 , Z. Xianzhi 1 , J. Lingong 1 , C. Fei 1 , S. Yuxin 1 , Q. Shuiwang 1 , G. Lei 1 , Z. Huojun 1 1 Changhai Hospital, Radiation Oncology, Shanghai, China ; 2 Affiliated Tumor Hospital of Guangxi Medical University, Radiation Oncology, Nanning, China ; 3 the General Hospital of Eastern Theater Command, Radiation Oncology, Nanjing, China Purpose or Objective To compare patterns of local failure and outcomes of biologically effective dose (BED 10 , α/β=10) of 60-70Gy with that over 70Gy for locally advanced pancreatic cancer. Material and Methods Patients with biopsy and radiographically proven locally advanced pancreatic cancer were included. Comparisons were performed after propensity score matching. Recurrences were plotted on a template CT scan, which were categorized as in-field, marginal and outside-the- field recurrence. ΔGTV was defined as the volume of primary recurrence minus by that of primary lesion before SBRT. Results A total of 527 and 493 patients received BED 10 of 60-70Gy and over 70Gy. After propensity score matching, there were 486 patients in each group. The median overall survival (OS) of patients with BED 10 over 70Gy and of 60- 70Gy was 20.3 months (95%CI: 19.1-21.5 months) and 18.2 months (95%CI: 17.8-18.6 months), respectively (P<0.001). The progression free survival (PFS) of the two cohorts was 15.4 months (95%CI: 14.2-16.6 months) and 13.3 months (95%CI: 12.9-13.7 months), respectively (P<0.001). The median ΔGTV of two groups was 55.97cc (range: 7.15- 99.72cc) and 63.37cc (range: 20.15-108.79cc) (P<0.001). More patients with BED 10 of 60-70Gy had recurrences at the hepatic hilum than those with BED 10 >70Gy (37/486 vs. 21/486, P=0.03) in addition to primary recurrences. A higher incidence of in-field and marginal recurrence was found in patients with BED 10 of 60-70Gy (in-field: BED 10 of 60-70Gy: 97/486 vs. BED 10 >70Gy: 72/486, P=0.034; marginal: BED 10 of 60-70Gy: 109/486 vs. BED 10 >70Gy: 84/486, P=0.044). However, more patients with BED 10 >70Gy had grade 2 or 3 acute and late gastrointestinal toxicities than those with BED 10 of 60-70Gy (acute gastrointestinal toxicity: BED 10 >70Gy: 87/486 vs. BED 10 of 60-70Gy: 64/486, P=0.042) (late gastrointestinal toxicity: BED 10 >70Gy: 77/486 vs. BED 10 of 60-70Gy: 55/486, P=0.039). Conclusion Significant survival benefits were found in BED 10 >70Gy. Additionally, a higher incidence of in-field and marginal recurrence and more local recurrent lesions were found in BED 10 of 60-70Gy. Nevertheless, more patients with BED 10 >70Gy had acute and late gastrointestinal toxicities. Therefore, a higher dose may be required in the case of patients’ well tolerance and no compromise of dose constraints of organs at risk.

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 (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