ESTRO 2020 Abstract book

S300 ESTRO 2020

for late onset of loco-regional and distant recurrence should not be underestimated. Usually surgery is the mainstay of treatment of malignant salivary tumors, almost always followed by radiation therapy. Surgery is dictated by the site of the tumor and may include parotidectomy, excision of the submandibular gland (including level Ia, IIb and III) or excision of the lesion of the oral cavity (e.g. palate or tongue), oropharynx or elsewhere), with appropriate reconstruction if necessary. Currently surgery is histology independent, but histology- driven surgery in parotid carcinoma may be on future’s doorstep. SP-0505 Particle therapy for salivary gland tumors A. Jensen 1 University Hospitals Gießen and Marburg UKGM- Philipps- University Marburg, Department of Radiation Oncology, Waghäusel, Germany Abstract text Salivary gland malignancies comprise a heterogenous group of rare cancers characterized by aggressive local growth. Due to their sometimes uncharacteristic symptoms, patients are often diagnosed with advanced disease. Especially in the paranasal sinuses both surgical and radiooncological approaches remain a challenge in view of close proximity to critical structures.High-LET radiation with neutrons initially resulted in superior local control rates albeit at substantial long-term toxicities. In contrast to neutrons, charged particles such as protons or C12 carbon ions deposit most of their energy at the end of their path, allowing highly conformal dose distributions at complex anatomical sites while maintaining normal tissue sparing. In view of the rarity of the disease, analyses of homogenous large cohorts are or even prospective trials are rare. Recent analyses concentrate on C12 and could show promising control and survival rates even in patients with advanced stages. Dose escalation with particle therapy was shown to improve both local control as well as overall survival at very moderate toxicities. Sufficient dose application provided, debulking surgery does not seem to result in improved control rates. Pooled as well as prospective data confirmed these findings. Management of local recurrence following full radiotherapy in the head and neck in general and in salivary gland malignancies in particular remains a challenge for all disciplines. In cases where surgical salvage is not possible or feasible, systemic agents so far only achieve limited response. Particle therapy for high-dose re-irradiation may be feasible and can achieve promising response rates with moderate toxicity. Further dose escalation has to be considered with caution due to the risk of excessive late toxicity. Finally, with health systems are increasingly under pressure from a variety of costly new treatment options. Faced with finite resources, most health systems require formal cost- effectiveness evaluations in order to accept new treatments as a new standard. Based on retrospective cohorts, cost-effectiveness of particle therapy in MSGTs may potentially be supported.In summary, particle therapy is a good treatment option with promising local control especially in advanced MSGTs. The use of tumour debulking surgery in advanced ACC may have to be reconsidered. In cases of local tumour relapse, C12 may be a good option when surgery is not feasible but has to be used with caution. Cost-effectiveness of particle therapy over standard IMRT may be established in MSGT.

SP-0501 When to omit radiotherapy in rectal cancer? E. Rullier CHU Bordeaux, France

Abstract not received

SP-0502 Organ preservation: where are we and where do we go? K. Haustermans University Hospital Gasthuisberg, Leuven, Belgium

Abstract not received

SP-0503 The total neoadjuvant approach: when and where to add chemotherapy in rectal cancer E. Fokas 1 1 Klinikum der Johann Wolfgang Goethe Univ, Department of Radiotherapy and Oncology, Frankfurt, Germany Abstract text Clinical trials assessing the role of adjuvant chemotherapy (CT) for rectal cancer have been characterized by inconsistent oncological outcome results and poor compliance. Total neoadjuvant therapy (TNT), in which chemoradiotherapy (CRT)/short-course radiotherapy (SCRT) and CT are delivered in the preoperative setting, is a new paradigm for rectal cancer treatment. Here, the rationale for TNT in rectal cancer will be discussed. Despite the increasing interest in the concept of TNT for rectal cancer, optimal scheduling of preoperative CRT/CRT and CT (induction vs consolidation) remains to be established. As such, the prons and cons of the two different TNT sequences will be presented. Finally, the current evidence on the impact of TNT on oncological outcome and quality of life in patients with rectal cancer will be summarized. SP-0504 Surgical approaches for salivary gland tumors C.R. Leemans 1 1 Amsterdam University Medical Centres, ORL-HNS, Amsterdam, The Netherlands Abstract text Salivary malignancies are rare head and neck tumors that comprise a very variable histology. This subtyping and staging determine the course of disease and outcome. They require expert multidisciplinary management for the best outcome. Some of the commonest subtypes will be discussed in more depth. In adenoidcystic carcinoma (ACC) T-stage, N-status, surgical margins, presence of any solid component in and age are the main predictors of survival- outcome in ACC of the head and neck. Distant metastasis frequently develop, mainly in the first 5 years post treatment. Local recurrences often develop even later on, warranting long term follow up of patients treated for ACC. Grade III ACC should be considered a specific entity within the group of ACC due to its typical aggressive biological behaviour and relatively poor outcome, implicating the need for an improved adjuvant treatment. Mucoepidermoid carcinoma (MEC) of the head and neck has a favourable outcome with the exception of high grade MEC. Perineural infiltration and nodal involvement are not rare. The importance of the CRTC1/3 MAML 2 fusion gene with respect to prognosis remains unclear. The tendency Symposium: Multidisciplinary treatment of salivary gland tumors