ESTRO 2020 Abstract book

S146 ESTRO 2020

SP-0265 Is there a role for particle therapy in the treatment of locally advanced pancreas cancer ?" P. Fossati 1 , P. Georg 1 , E. Hug 1 1 EBG Medaustron Gmbh, Radiotherapy, Wiener Neustadt, Austria Abstract text Cancer of the exocrine pancreas can still be considered an unsolved clinical problem. An epidemiological analysis form 2012 has shown that in Europe incidence equals mortality. This dismal outcome is driven both by the high rate of patients that are already metastatic at diagnosis (or that develop metastases early in the course of their disease) and by the difficulties in achieving local control even in the non-metastatic patients. Aggressive chemotherapy can achieve a survival advantage both in metastatic and locally advanced cases. Radiotherapy has been used in the attempt to increase local control both preoperatively, and postoperatively but its role as exclusive local treatment is still questionable. Particle therapy with protons or carbon ions has several dosimetric advantages in comparison with standard radiotherapy with photons. Particles display an inverse depth dose profile with a finite range; therefore they can achieve a conformality that is similar to that of the most advanced photons-based techniques, while substantially reducing the integral dose to the patient and the middle and low dose bath. Carbon ions, besides their favorable physical properties, have a radiobiological advantage: in the last part of their track, they produce dense ionizations that create DNA damages that are more difficult to repair. These damages can kill cells almost independently from the oxygenation level and this is particularly relevant for pancreatic cancer that is a disease with a thick fibrotic stroma and many hypoxic niches. The use of proton and carbon ions in the treatment of pancreatic cancer has the potential to reduce the dose to the small bowel and stomach thus reducing the risk of acute and late gastro intestinal toxicity. Moreover, the sparing of the healthy tissues, i.e. the bone marrow, but most importantly the spleen, can reduce hematological toxicity and improve tolerance to concomitant chemotherapy. Particle therapy can therefore be used to reduce toxicity and to increase the delivered dose and, at least for carbon ions, the radiobiological efficiency of the dose, in the attempt to improve local control. Protontherapy has been used in the preoperative treatment of pancreatic cancer mainly at Massachusetts General Hospital. An aggressive combination of chemotherapy with FOLFIRINOX, radio- chemotherapy (with protons or photons according to the availability) and surgery has achieved a 3YOS in excess of 60%, which is more than double of what is expected in this population. Also in the experience of University of Florida protontherapy concomitant to chemotherapy could convert to resectability a significant percentage of locally advanced cases without any increase in intra and perioperative morbidity. Finally, carbon ion radiotherapy has been employed in Japan with excellent results both in the preoperative setting and for locally advanced cases. The initial results of the National Institute of Radiological Sciences in Chiba have been recently confirmed in a prospective multi-centric study in Japan . In these series, 2YOS in excess of 50% has been reported for inoperable patients without surgery. The Japanese experience is extremely relevant also in terms of target volume definition, which is based on an extensive review of pathological series assessing the risk of nodal involvement in each of the lymph-node station in the upper abdomen (according to the Japanese Pancreas Society ‘JPS’

classification). The target volumes employed are also modified to account for the risk of perineural spread. An international multi-centric prospective randomized phase III trial (CIPHER, Identifier: NCT03536182) of carbon ion radiotherapy vs. photons IMRT in patient with locally advanced pancreatic cancer has been designed to verify this survival advantage. This trial will randomize patients with locally advanced pancreatic cancer to receive either IMRT with photons in their home country (USA, South Korea, Italy and Japan) or carbon ion radiotherapy in Japan and Italy. In summary particle therapy can achieve an improved local control with reduced toxicity both as preoperative and as exclusive treatment. Large multicentric prospective trials are needed. The combination of Carbon ion radiotherapy and FOLFIRINOX has still to be tested and could potentially result in an even better local control. SP-0266 Scheduling radiotherapy and drug treatments for pancreatic cancer T. Brunner 1 1 Otto-von-Guericke-Universität, Dept. Radiation Oncology, Magdeburg, Germany Abstract text Pancreatic cancer is the most lethal gastrointestinal tumour. Chemotherapy is the mainstay of therapy in the majority of the patients whereas resection is the only chance of cure but only possible in 15-20% of all patients. The integration of radiotherapy into multimodal treatment concepts is heavily investigated. It is now commonly accepted that induction chemotherapy should precede radiotherapy. When fractionated conventionally it should be given as chemoradiotherapy. Recently, stereotactic body radiotherapy emerged as an alternative, but will have to be carefully investigated in clinical trials. We aim to give an overview of radiotherapeutic strategies with a focus on the latest developments in the field in the context of chemotherapy and surgery. Furthermore, novel systemic combinations in combination with radiotherapy will be briefly summarised. Finally, supportive therapy with drug treatment, especially prophylactic therapy of gastroduodenal toxicity will be discussed. SP-0267 Guideline proposal from the first ESTRO Physics workshop: RAdiotherapy Treatment plannINg study Guidelines (RATING) C.R. Hansen 1 1 Odense University Hospital, Department of Oncology, Odense, Denmark Abstract text Treatment planning is a central part of radiotherapy and high quality treatments are important for the outcome of the treatment, both in terms of survival and toxicity. However, published treatment planning studies are of very varying quality and their conclusions might not always be generalizable due to questionable study setup. At the first ESTRO physics workshop it was decided to construct a guideline for planning studies, to help researcher and clinicians conduct high quality studies. The guidelines go through most of the aspects that planning studies need consider and address. For each focus point, there are recommendation on what needs to be part of the study and Symposium: How to enhance the quality of treatment planning studies

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