ESTRO 2020 Abstract Book

S420 ESTRO 2020

irradiation. A pooled meta-analysis of 3 randomized clinical studies reported that consolidation thoracic radiotherapy significantly improved the progression-free survival, and reduced thoracic failures [Rathod S, EJC 2019]. However, no significant benefits in overall survival were observed with consolidation thoracic radiotherapy (HR 0.88, 95% CI 0.66-1.18). Two randomised clinical studies in patients with extensive SCLC have evaluated the combination of anti-PD-L1 antibodies with chemotherapy versus chemotherapy alone. Both the IMpower 133 study evaluating atezolizumab [Horn L, NEJM 2018] and the CASPIAN study evaluating durvalumab [Pas-Arez L, Lancet 2019] included similar patient populations and reported similar adverse events. Both studies had explicitly excluded the use of planned thoracic radiotherapy, and both reported statistically significant improvements in overall survival, although the benefits were clinically modest. These findings have led to approval by the United States FDA for atezolizumab in patients with previously untreated extensive-stage SCLC, and the use of durvalumab is under priority review at the FDA. The feasibility of incorporating concurrent thoracic radiation with a PD-1 checkpoint inhibitor (pembrolizumab) after induction chemotherapy for extensive SCLC, has been reported as feasible [Welsh J, JTO 2019]. Future studies evaluating thoracic radiotherapy in the era of immune checkpoint inhibitors will have to address factors such as disease load (limited volume vs truly extensive disease), the timing of thoracic radiotherapy (sequential vs concurrent) and optimal radiation doses. No biomarkers that could identify patients who are likely to benefit from immune checkpoint inhibitors have been identified. Similarly, the proposed new nomenclature for SCLC subtypes, defined by relative expression of four key transcription regulators [Rudin CM, Nat Rev Med 2018], remains to be studied in trials. Limited SCLC The standard of care in patients with limited stage SCLC is concurrent chemo-radiotherapy, followed by prophylactic cranial irradiation. The role of immune checkpoint inhibitors is an active area of research. Randomized trials evaluating these agents in the consolidation setting after completion of chemo- radiotherapy include NCT02046733 (ipilimumab- nivolumab), NCT03540420 (atezolizumab) and NCT03703297 (durvalumab +/-tremelimumab). Trials evaluating checkpoint inhibitors concurrently with thoracic chemoradiotherapy include NCT03509012 (durvalumab +/- tremelimumab), NCT02402920 (pembrolizumab), NCT03585998 (durvalumab) and NCT03811002 (atezolizumab). SP-0762 Stereotactic ablative radiotherapy for refractory ventricular tachycardia R. Jumeau 1,2 1 centre Hospitalier Universitaire Vaudois, Department Of Radiation Oncology, Lausanne, Switzerland ; 2 riviera- Chablais Hospital, Radiation Oncology Unit, Rennaz, Switzerland Abstract text Ventricular tachycardia (VT), an important cause of mortality and morbidity, commonly occurs in the context of structural heart diseases. Antiarrhythmic drug therapy (AAD) and catheter ablation are the cornerstone of VT management, but both treatments have limited efficacy Symposium: Current status of radiotherapy for non- malignant disease outside the brain

and potential adverse effects. Additionally, despite significant progress in catheter ablation efficacy, the recurrence rate after a first VT ablation is about 50%, exposing patients to multiple CA procedures and implantable cardioverter-defibrillator shocks. Stereotactic body radiotherapy (SBRT) is routinely used in oncology to treat non-invasively solid tumors with high precision and efficacy. Recently, this technology has been evaluated for the treatment of VT. This lecture will present the basic underlying principles, proof of concept and main results of trials and case series that used SBRT for the treatment of VT refractory to AAD and catheter ablation. SP-0763 The role of radiotherapy in the management of painful inflammatory diseases L. Miszczyk 1 , L. Tomasz 1 , M. Miszczyk 2 1 maria Sklodowska-Curie Memorial Cancer Center And Institute Of Oncology, Radiotherapy, Gliwice, Poland ; 2 maria Sklodowska-Curie Memorial Cancer Center And Institute Of Oncology, 3rd Radiochemotherapy Ward, Gliwice, Poland Abstract text Introduction: There is a wide selection of painful inflammatory diseases treated with irradiation. Even in our institution we deal with seven of them: PHS (periarthritis humeroscapularis), EPH (epicondylitis humeri), HSS (heel spur syndrome), Achilles tendonitis and rarely with gonharthritis, painful chronic ostitis and painful osteoporotic fractures of vertebras. Due to the limited presentation time, I will focus only on the first three mentioned. Purpose: An evaluation of the effectiveness of PHS, EPH and HSS radiotherapy. Material and method: After a long period of limited interest in this kind of treatment, in the late nineties in Gliwice we launched it again, hence we have 20 years long experience with this form of radiotherapy. In this presentation I would like to show and compare two sets of results for each disease – older and actual (now, ongoing – incomplete analysis). In all the cases, the patients were irradiated using two opposite fields using a 2D technique. Results: PHS: The first analysis was completed in 2004 and compared 30 cases with a mean FU of 18 months. All were irradiated using 60 Co gamma beams with 1 Gy fd to TD of 6 Gy. The mean of pain relief was 93% one year after the treatment. The second analysis comprised 119 cases irradiated with 6 MV photons using 1 Gy fd to TD of 6 Gy. The mean of pain relief was 27% 1 month after the treatment and 53-83% in the time of the next controls. During the last control, 33% of patients reported complete pain relief, 27% relief larger than 50% and 8.5% relief lower than 50%. HSS: The first analysis was conducted in 2006 and comprised 623 heel spurs irradiated using X-rays (97%), 60 Co gamma beams, electrons and high energy photons with a fraction dose of 1-3 Gy to a total dose of 1- 45 Gy. After treatment 48% of the patients reported a lack of pain, 21% reported pain relief greater than 50% and 17% reported pain relief less than 50%. The mean of pain relief duration was 72 months. The second analysis (mean of FU 60 months) comprised 55 patients irradiated between 2013-2016 with 6 MV photons using 1 Gy fd to a TD of 6 Gy. 64 % of them reported pain relief at the end of RT (50% pain reduction). Duration of pain relief was in the range of 10 to 64 months. EPH: The first analysis was performed in 2015 and comprised 50 cases (mean FU 15.2 months) treated using 6 MV photons with 1 Gy fd to a TD of 6 Gy. The mean of pain relief was 70.2% one year after the treatment. As yet we have the very preliminary data from