ESTRO 2020 Abstract Book

S647 ESTRO 2020

Conclusion When combined with ipi at 10 mg/kg, the MTD of RT was 9 Gy. This combination of ipi + RT appeared to be associated with antitumor activity. Ipi + RT could increase CD4+ and CD8+ ICOS+ T cells. Increased CD8+ was significantly associated to PFS. Thus, immune biomarkers may be useful for early response evaluation. ΔTGR non-irr lesions could be more important than for irradiated lesion in responding pts and may be related to abscopal effect. PO-1228 Stereotactic radiosurgery with concurrent immunotherapy in malignant melanoma brain metastases J. Liermann 1 , M. Syed 1 , U. Neuberger 2 , D. Reuss 3 , R. El Shafie 1 , W. Julia 4 , J. Debus 1 , J. Hassel 4 , S. Rieken 5 1 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany ; 2 Heidelberg University Hospital, Department of Neuroradiology, Heidelberg, Germany ; 3 Heidelberg University Hospital, Institue of Pathology, Heidelberg, Germany ; 4 Heidelberg University Hospital, Department of Dermatology, Heidelberg, Germany ; 5 Goettingen University Hospital, Department of Radiation Oncology, Goettingen, Germany Purpose or Objective Stereotactic radiosurgery (SRS) is an established treatment for brain metastases in the management of malignant melanoma. The increasing use of checkpoint inhibitors in melanoma therapy leads to combined treatment schemes consisting of immunotherapy and SRS that need to be evaluated regarding safety and feasibility. Material and Methods We retrospectively analysed 36 patients suffering from malignant melanoma with brain metastases. Between November 2011 and May 2016, a total of 66 brain metastases were treated with single-fraction SRS (22.5-25 Gy prescribed to the 80% isodose) in combination with a checkpoint inhibitor (Ipilimumab: 82%, Pembrolizumab: 14% or Nivolumab: 4%), applied within 3 months before or after SRS. Toxicity was evaluated with focus on the incidence of radiation-induced cerebral necrosis. Overall survival (OS) and intracranial Progression free survival (PFS) were analysed using the Kaplan-Meier method. Results The median follow-up was 24.9 months (range: 1.9-115.5 months). SRS was well tolerated. No clear SRS-induced CTCAE °III or °IV toxicity could be seen. Severe neurological symptoms (seizures, aphasia or neurocognitive deficiency) were either due to tumor progression or a result of additional whole brain radiotherapy before (11%) or after (22%) SRS. During follow-up, seven of the growing contrast-enhanced lesions were resected, revealing three cases of radiation-induced necrosis and four cases of local tumor progression. Altogether, the observed radiation necrosis rate of the irradiated metastases was 6-18% (the range is due to the radiologically challenging differentiation between radiation necrosis and tumor progression). Median OS was 22.2 months. Intracranial median PFS was 5.8 months. Conclusion In the presented cohort, the combination of SRS and checkpoint inhibitors in the management of malignant melanoma brain metastases was safe and effective. To gain resilient data, prospective trials are needed.

Center of Oncological Hadrontherapy CNAO, Radiotherapy Unit, Pavia, Italy ; 3 University of Palermo, Radiation Oncology School, Palermo, Italy ; 4 University of Milan, Department of Oncology and Hemato-Oncology, Milano, Italy Purpose or Objective Evaluation of long term toxicity profile in young patients treated with particle therapy for chordoma at CNAO. Chordomas are rare slow-growing tumors characterized by a locally aggressive growth pattern, representing 50-60% of bone tumors. The 50–60% of cases are localized in the sacrum-coccix followed by skull-base (25–30%), cervical (10%) and thoracolumbar tract (5 %). The site of origin is commonly located nearby organs performing important functions. The main treatment for chordoma is still represented by radical surgery. In most cases the resection with wide margins is complicated by severe dysfunctions that can be highly disabling with remarkable impact on quality of life (QoL) and socio-economics contribution, especially in young patients. In the last decades particle therapy seems to be a safe alternative to radical surgery in sacral chordoma, and the best radiotherapy technique in post-operative treatment of skull-base and spine chordoma in terms of local control and lower late effects. Aim of the study is to evaluate toxicity and quality of life in young patients undergoing hadrontherapy for chordoma. Material and Methods Between June 2012 and December 2018, 36 young pts with median age of 36 years (9-40) with histologically proven chordoma, were treated with charged particle therapy using active scanning beam delivery system at CNAO. We treated 22 skull-base chordomas, 9 spine chordomas (level from C1 to L5) and 5 sacral chordomas (level S1-S3 and below). 17 pts were treated with proton therapy (PT) median dose 74Gy RBE (range 36-74) while 19 pts with carbon ion therapy (CIRT) with median dose 70.4Gy RBE (range 64-73.6). We evaluated toxicity according to CTCAE v.4 and investigated QoL using EORTC QLQ-C30 questionnaires. Results Median follow-up time was 26 months. Late G3 toxicity was observed in 2 patients with skull-base chordoma (skin ulceration with consequential synthesis media exposure and seizures). Temporal lobe necrosis G2 was observed in 4 patients, G1 in 2 patients. Six patients with spine/sacral chordoma developed neurosensitive peripheral neuropathy: 3 patients experienced G1 toxicity, 3 patients G2 toxicity. No one showed bladder or bowel dysfunctions. No patient had walking impairment. Conclusion These data seem to confirm an encouraging long-term toxicity profile in young patients treated with particle therapy for chordoma, taking into account the lower late severe side effects compared to the disabilities expected from aggressive surgery. All patients were able to keep working and having a normal social life after treatment. Nevertheless a longer follow is required to confirm our preliminary results. PO-1230 The role of adjuvant boost in local control for high grade sarcomas with low necrosis scores PO-1231 Adjuvant radiotherapy for high-grade dedifferentiated liposarcoma in elderly patients:a case series Y. Pan 1 1 Taipei Veterans General Hospital, Division of Radiation Oncology- Department of Oncology, Taipei, Taiwan Purpose or Objective Dedifferentiated liposarcomas (DDLPS) are aggressive malignant tumors of adipocytic differentiation. They are Abstract withdrawn

Poster: Clinical track: Sarcoma

PO-1229 Preliminary data on long term toxicity in young patients with chordoma: C.N.A.O. experience E. Scipilliti 1 , M.R. Fiore 2 , F. Cuccia 3 , S. Durante 4 , S. Ronchi 2 , M. Bonora 2 , A. Barcellini 2 , F. Valvo 2 1 University of Naples "Federico II", Department of Advanced Biomedical Science, Napoli, Italy ; 2 National