ESTRO 2020 Abstract book

S695 ESTRO 2020

treated with pre-op RT and a post-operative RT boost. We retrospectively reviewed our sarcoma database to determine whether giving a post-operative boost in patients with <50% necrosis scores actually reduces the risk of local recurrence. Material and Methods An IRB approved retrospective chart review was performed for extremity sarcoma patients treated with pre-operative RT of 3.5 Gy x 8 in our institution's department of Radiation Oncology between 2002-2013. The distribution of histologies treated was: high grade NOS (9), synovial (7), liposarcoma (3), myxofibrosarcoma (3), Chondrosarcoma (2), and other (4). A total of 28 patients were identified. Information regarding patient baseline characteristics, treatment regimens, necrosis score, and ultimate treatment outcomes were collected. Time to failure was determined from time of biopsy to time of either local or distant recurrence. Kaplan-Meier curves were generated for overall survival. Results Median follow-up for the entire cohort was 36 months. Median age of the entire cohort was 47 years old. The preoperative tumor size was: < 5 cm (4), 5-10 cm (13), and 10 cm (11). Tumor location was upper extremity (8) and lower extremity (20). When post-operative RT was given, the median dose was 28 Gy. Conclusion The local recurrence risk in the entire cohort of patients was 4%. These data do not demonstrate an increased risk of local recurrence in patients with < 50% necrosis score. Distant metastasis and overall survival are poor in this cohort of patients demonstrating a need for improved treatments. 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 characterized by local recurrence in at least 40% of cases, and distant metastases in 15–20% of cases. Surgical resection has been the mainstay of management, and adjuvant radiotherapy is often considered due to the difficulty of complete resection. Though the peak incidence of DDLPS occurs in patients’ 50s, the number of extreme elderly patients with DDLPS has increased with the rise in the aging population. Therefore, the current study investigated the clinical outcomes of adjuvant radiotherapy in extreme elderly patients with high-grade nonmetastatic dedifferentiated liposarcoma of trunk, extremities and retroperitoneum. Material and Methods We retrospectively analyzed twenty-eight patients beyond 80-year-old with locally advanced DDLPS, who underwent surgical resection and adjuvant radiotherapy between 2003 and 2018 in a tertiary centre. All patients were treated with curative intent. Overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method. Histological grading was reviewed according to the National Federation of Centers for the

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 B. Odei 1 1 The James Cancer Hospital- Ohio State University, Radiation Oncology, Columbus, USA Purpose or Objective Patients with high grade extremity sarcomas are at high risk for local and distant recurrence. Our institution developed a novel pre-operative chemoradiotherapy regimen that shortens the duration of radiation (RT) and allows for safe and early administration of chemotherapy. Early observations using this regimen demonstrated higher local recurrence for patients with a necrosis score of < 95% at the time of surgery. Based on this data, patients with < 50% necrosis scores were often This abstract has been withdrawn from presentation