ESTRO 2023 - Abstract Book

S1264

Digital Posters

ESTRO 2023

Oligometastatic STS patients treated with LTs experience a satisfying LC rate, without significant differences between SBRT or surgery, long progression-free interval and promising OS. Polymetastatic conversion is a late event, in particular in patients with a long interval from primary diagnosis to first metastatic relapse. Repeated LTs could be administered to extend disease control.

PO-1557 RT after Encorafenib and Binimetinib on BRAF mutated melanoma brain metastases. GEM1802-Phase II

A. Alvarez 1 , I. Valduvieco 2 , A. Arance 3 , R. Delgado 4 , M.A. Berciano 5 , F. López Campos 6 , A. Soria 7 , J.L. Romero 8 , P. Sánchez Mauriño 9 , A. Lucas 10 , J. Martín Liberal 11 , P.J. Prada 12 , A. García Castaño 13 , M.C. Alamo 14 , E. Puertas 15 , M. González Cao 16 , A. Conde 17 , R. Díaz Beveridge 18 , J.A. Corona 19 , C. Aguado 20 , P. Foro 21 , J. Vidal 22 , F. López Soler 23 , P. Cerezuela Fuentes 24 , I. Márquez Rodas 25 1 HGU Gregorio Marañón, Radiation Oncology, Madrid, Spain; 2 H Clinic, Radiation Oncology, Barcelona, Spain; 3 H Clinic, Medical Oncology, Barcelona, Spain; 4 H Regional de Málaga, Radiation Oncology, Malaga, Spain; 5 Unidad de Gestión Intercentros. H U Regional y Virgen de la Victoria. IBIMA., Medical Oncology, Málaga, Spain; 6 H. Ramón y Cajal, Radiation Oncology, Madrid, Spain; 7 H Ramón y Cajal, Medical Oncology, Madrid, Spain; 8 HU Reina Sofía, Radiation Oncology, Córdoba, Spain; 9 HU Reina Sofía, Medical Oncology, Córdoba, Spain; 10 ICO L´Hospitalet, Radiation Oncology, Barcelona, Spain; 11 ICO L´Hospitalet, Medical Oncology, Barcelona, Spain; 12 H Valdecilla, Radiation Oncology, Santander, Spain; 13 H Valdecilla, Medical Oncology, Santander, Spain; 14 HU Virgen de la Macarena, Medical Oncology, Sevilla, Spain; 15 HU Dexeus, Radiation Oncology, Barcelona, Spain; 16 HU Dexeus, Medical Oncology, Barcelona, Spain; 17 H la Fe, Radiation Oncology, Valencia, Spain; 18 H la Fe, Medical Oncology, Valencia, Spain; 19 H Clínico San Carlos, Radiation Oncology, Madrid, Spain; 20 H Clínico San Carlos, Medical Oncology, Madrid, Spain; 21 H del Mar, Radiation Oncology, Barcelona, Spain; 22 H del Mar, Medical Oncology, Barcelona, Spain; 23 HCU Virgen de la Arrixaca, IMIB, Radiation Oncology, Murcia, Spain; 24 HCU Virgen de la Arrixaca, IMIB, Medical Oncology, Murcia, Spain; 25 HGU Gregorio Marañón, Medical Oncology, Madrid, Spain Purpose or Objective Encorafenib and binimetinib (EB) have shown intracranial activity in patients with BRAF mutated melanoma and brain metastases (BM). Since targeted therapy responses seem to be shorter than immunotherapy, we explore the role of radiation therapy (RT) after 2 months of EB treatment as a potential way to improve the duration of response. Materials and Methods GEM1802 was a prospective phase II clinical trial (NCT03898908) that evaluated EB (450 mg pd E + 45 mg bd B) in patients (p) with BM during 56 days (d) followed by brain RT (local or WBRT) and EB until disease progression. Two cohorts were planned: C1 (N=48), asymptomatic; and C2, symptomatic p (N=15). Primary endpoint was intracranial response rate (icRR) after 56d of EB, before RT in C1. RT was planned only in cases of partial response (PR) or stabilization (SD). In case of complete response (CR), it was omitted until progression. Results We report preliminary results first 47 pts, 42 of them were evaluable for RT (27p C1/15p C2). Median Follow-up 12.3 m (9.5-16.1). Primary endpoint icRR before RT was 66,7% in C1 (73.3% in C2). No patient progressed during EB. 30 p received RT (1p CR, 8p PR and 6p SD), and 12 p (4p CR, 6p PR and 2p SD) did not. RT consisted on local treatment in 15p (12 C1 and 3 C2) and WBRT in 15p (8 C1 and 7 C2). There were no differences in the main prognostic factors according to RT treatment (yes/no), except for gender distribution (92% females in Non-RT vs 37% RT, p 0.002). Estimated IPFS (intracranial progression-free survival) at 12m was 21,46% vs 41,67 % for RT yes/no respectively (p 0.469), both groups with similar median (8.26 m vs 7.37 m). Patients in C2 that did not achieve intracranial complete response and received RT had a numerically longer duration of response than those that did not received (Table 1). Table1. Duration of response (median months-95% CI, descriptive analysis):

There RT. Overall Last status: 27p (64.3%) have died (15p-55.6% C1 and 12p-80% C2), 23 of them had received RT (76.7%). Conclusion In this preliminary analysis, encorafenib and binimetinib showed intracranial activity in patients with BRAF brain metastases of melanoma similar to other targeted therapies. Radiation therapy could increase the duration of response only in symptomatic patients, especially if local techniques are used, although this observation should be tested prospectively. was no significant increase in toxicity with the addition of

PO-1558 Five-fraction protontherapy for skull base chordomas and chondrosarcomas: first experience

M. Sallabanda 1 , J.A. Vera 2 , J.M. Pérez 2 , M. Montero 1 , A. de Pablo 1 , R. Matute 1 , J. Castro 2 , F. Cerrón 2 , A. Mazal 2 , R. Miralbell 1

1 Centro de Protonterapia Quirónsalud, Radiation Oncology, Madrid, Spain; 2 Centro de Protonterapia Quirónsalud, Medical Physics, Madrid, Spain