ESTRO 2021 Abstract Book

S1011

ESTRO 2021

Hospital – Università Cattolica del Sacro Cuore, Campobasso, Italy

Purpose or Objective The role of proton beam radiotherapy (PBRT) in pancreatic cancer (PCa) is still uncertain due to lack of randomized trials or systematic review. The aim of this study was to analyse available evidence on this topic. Materials and Methods A bibliographic search was performed using PubMed, Scopus, and Cochrane databases. All studies in English language reporting toxicities and/or outcomes data on PBRT in PCa were included. Results Ten studies were included: five retrospective reports, three simply defined as prospective trials, and two prospective phase I/II trials. Total number of involved subjects was 362 patients: 269 with locally advanced pancreatic cancer (LAPC), 45 with locally recurrent PCa, and 48 with resectable PCa. Median follow-up ranged between 10 and 38 months (median: 15 months). PBRT was performed with concurrent chemotherapy in all studies, with doses ranging between 25.0 and 70.2 GyE (median: 67.5 GyE). Acute and late grade ≥ 3 gastrointestinal (GI) toxicity was observed in all studies, ranging from 3.0% to 20.0%, and from 2.5% to 20.0%, respectively with the highest toxicity rate (20.0%) reported in the study where the highest dose (70.2 GyE) was delivered. In two studies grade 5 late GI toxicity were recorded (2.2% and 2.5%). Median overall survival in LAPC ranged between 18.4 and 25.6 months (median: 20.8 months). Median progression-free survival in LAPC was recorded only in a study (15.4 months). Conclusion PBRT has clear dosimetric advantages making it an attractive treatment option but also an unclear role in PC. Our analysis showed a not negligible grade ≥ 3 toxicity rate with some lethal late effect. Overall survival, and progression-free survival rates were slightly higher than those recorded in studies based on photon radiotherapy. Therefore, further investigation on PBRT in PCa is needed. PO-1222 Robotic Stereotactic Radiosurgery for locally advanced pancreatic cancer-Local control and tolerance C. Silva 1 , M. Amorim 1 , M.A. Costa 2,1 , C. Fardilha 2,1 , J. Gagean 2,1 , J. Vale 2 , R. Guedes 2 , P. Genésio 2 , P. Vieira 2 , P. Costa 2,1 1 Hospital de Braga, Radiation Oncology, Braga, Portugal; 2 CUF Institute, Radiation Oncology - Júlio Teixeira S.A., Porto, Portugal Purpose or Objective Despite of new therapeutic approaches, including both systemic and local therapy, locally advanced pancreatic cancer (LAPC) has a poor prognosis. Standard doses of conventionally fractionated radiation have had minimal to no impact on the survival duration of patients with LAPC. However, stereotactic body radiotherapy (SBRT) using CyberKnife (CK), a highly conformal high-dose radiation per fraction, allows the precise delivery of a large ablative radiation dose to a tumour volume while sparing surrounding organs and tissues. This study was designed to evaluate the short-term efficacy and toxicity of image-guided robotic stereotactic radiosurgery- CK for locally advanced pancreatic cancer. Materials and Methods We analysed 9 patients with LAPC, ranging in age from 40 to 86 years (mean: 65), treated with robotic stereotactic radiosurgery-CK, from February 2017 to December 2020. All patients had previous systemic therapy, with no or minimal response. The median total prescription dose was 36 Gy (range 33-40 Gy) delivered in 3 to 6 fractions. The median BED was 111 Gy (range 87-144 Gy). The planning target volume (PTV) was defined as gross tumour volume (GTV) plus 2-3 mm, and at least 95% PTV should be covered by 80% isodose surface. The median volume of PTV was 63 cm³ (22-120 cm³). Results Of the 9 patients, 5 were male and 4 female. In 5 cases, the tumour was located at the pancreatic head and 4 at the pancreatic body. The median follow-up was 10 months (range 3-31 months). All patients completed the treatment prescribed, with a good tolerance. Two patients presented grade I nausea, and there was a case of grade II vomiting. There were no grade III/IV toxicity. The evaluation was performed with a CT scan and/or PET-CT scan. Local control was achieved in 7 patients, 4 with complete response and 3 with partial response. Two patients presented disease progression, mainly with hepatic metastases. The median OS was 10 months (range 3-31). By the time of the present analysis, and with a mean follow-up of 10 months, 4 patients remain with no evidence of disease. Conclusion The conformity and rapid dose fall-off associated with SBRT offer the potential for dose escalation. Image- guided robotic stereotactic radiosurgery with CK may be considered a treatment option to achieve local control of locally advanced pancreatic cancer, with limited toxicity to normal surrounding tissues. The use of a multi-fraction regimen and high total dose as allowable based on dose-volume constraints to organs at risk should be considered to minimize toxicity and improve local control outcomes. In the present study 44,4% of the patients remains with no evidence of disease, with a mean follow-up period of 10 months. Better understanding of biological mechanisms for tumour response underlying stereotactic radiosurgery

treatment for LAPC, will allow for additional improvements in disease control. However, long-term follow-up is necessary to evaluate the survival and late toxicity.

PO-1223 Prognostic factors affecting survival in gastric cancer patients in Albania: A retrospective study F. Kraja 1 , J. Dervishi 1 , A. Hoti 2 , E. Karaulli 1 , I. Akshija 3 , E. Hafizi 1 , S. Ademi 1 , E. Cuedari 1 , H. Kolani 4 , A. Dibra 4 , E. Celiku 4 , B. Kraja 5 1 University Hospital Center Mother Teresa, Oncology, Tirana, Albania; 2 University Hospital Center Mother Teresa, Radiology, Tirana, Albania; 3 University Hospital Center Mother Teresa, Statistics, Tirana, Albania; 4 University Hospital Center Mother Teresa, Surgery, Tirana, Albania; 5 University Hospital Center Mother