ESTRO 37 Abstract book

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ESTRO 37

external beam radiation therapy (EBRT) in patients with primary retroperitoneal soft-tissue sarcoma (RPS). Material and Methods We conducted a retrospective evaluation of patients with RPS who have been treated with IOERT at our institution since 1991. Patients treated for recurrent disease were excluded, leaving 69 patients for the final analysis. Median tumor size was 12.5 cm, most lesions were high grade (79%). Main histologies were as follows: well- differentiated liposarcoma 15%, leiomyosarcoma 26%, dedifferentiated liposarcoma 38% and others 22%. Surgery resulted in gross complete resection in 90%, but only 36% had microscopic negative margins despite multivisceral resections in 64%. All patients had IORT with a median dose of 12 Gy, 58 patients (84%) received additional perioperative EBRT (45% preop., 55% postop.) with a median dose of 45 Gy. Results Median follow-up for the entire cohort was 39 months and 54 months in surviving patients. Estimated 5-year-LC was 71%. In univariate analysis, LC was significantly associated with resection margin (5-year LC R0: 94%, R1: 52%, R2: 31%). Trends were present for gender, grading, and UICC stage. In multivariate analysis, only resection margin remained significant. Estimated 5-year OS was 63%. In univariate analysis, OS was significantly associated with grading, UICC stage, resection margin and timing of EBRT (5-year OS preop. 91% vs postop. 47% vs none 63%). In multivariate analysis, only timing of EBRT remained significant. Interestingly, neoadjuvant EBRT seemed superior while postoperative EBRT did result in even worse survival than no EBRT. Conclusion Combination of surgery, IOERT and EBRT resulted in very promising local control and survival. Complete resection remains the cornerstone of treatment as margin status was associated with local control and survival. EBRT should be preferably applied preoperatively. EP-1634 IOERT in locally recurrent high grade RPS: a retrospective single center analysis of 83 cases L. Saleh-Ebrahimi 1 , I. Alldinger 2 , M. Uhl 3 , S. Schimmack 4 , G. Mechtersheimer 5 , M. Büchler 4 , J. Debus 3 , R. Krempien 6 , A. Ulrich 4 , F. Roeder 1 1 University Hospital LMU Munich, Radiation Oncology, Munich, Germany 2 CPZ Düsseldorf, Surgery, Düsseldorf, Germany 3 University of Heidelberg, Radiation Oncology, Heidelberg, Germany 4 University of Heidelberg, Surgery, Heidelberg, Germany 5 University of Heidelberg, Pathology, Heidelberg, Germany 6 Helios Clinic Berlin-Buch, Radiation Oncology, Berlin- Buch, Germany Purpose or Objective To report our experience with surgery and intraoperative electron radiation therapy (IOERT) with or without external beam radiation therapy (EBRT) in patients with locally recurrent high-grade retroperitoneal soft-tissue sarcoma (RPS). Material and Methods We conducted a retrospective evaluation of patients with RPS who have been treated with IOERT at our institution since 1991. Patients treated for primary disease, suffering from low grade tumors or with distant metastases were excluded, leaving 83 patients for the final analysis. Median tumor size was 9 cm with undifferentiated liposarcoma being the dominating

histology (61%). Lesions were grade 2 in 34% and grade 3 in 66%. Surgery resulted in gross complete resection in 94%, but only 19% had microscopic negative margins despite multivisceral resections in 58%. All patients had IOERT with a median dose of 15 Gy, 53 patients (64%) received additional perioperative EBRT (23% preop., 77% postop.) with a median dose of 45 Gy. Results Median follow-up for the entire cohort was 35 months and 43 months in surviving patients. Estimated 5-year-LC was only 35%. In univariate analysis, LC was significantly associated with UICC stage while only trends were present for grading, T stage and addition of EBRT. In multivariate analysis, only grading (5yr-LC G2 59% vs G3 22%) was found to be a significant factor regarding LC. Estimated 5-year OS was 48%. In univariate analysis, OS was significantly associated with grading and resection margin. Interestingly, only the achievement of gross total resection (GTR) was beneficial (5yr-OS GTR 55% vs no GTR 0%), while microscopic margin status (R0 vs R1) did not influence OS significantly. In multivariate Analysis,GTR remained the only significant factor for OS. Conclusion Outcome of recurrent high grade RPS was clearly worse compared to primary cases even after combination of surgery, IORT and EBRT. Reasonable efforts should be made already during primary treatment to prevent the onset of local recurrences. Prognostic factors may differ from primary cases and should be transferred with caution. GTR remained the only factor with significant impact on OS in multivariate analysis. EP-1635 Stereotactic body radiation therapy for lung metastases from soft tissue sarcoma: long term results L. Di Brina 1 , P. Navarria 1 , F. De Rose 1 , D. Franceschini 1 , C. Iftode 1 , A. Tozzi 1 , A. Marrari 2 , V. Quagliuolo 3 , M. Scorsetti 4 1 Humanitas Clinical and Research Center, Radiotherapy and Radiosurgery Department, Rozzano Milan, Italy 2 Humanitas Clinical and Research Center, Medical Oncology Department, Rozzano Milan, Italy 3 Humanitas Clinical and Research Center, Surgical Oncology Department, Rozzano Milan, Italy 4 Humanitas University, Department of Biomedical Sciences, Rozzano – Milan, Italy Purpose or Objective Patients with lung metastases (LM) from soft-tissue sarcomas (STS) have been treated with surgery and/or chemotherapy in the last decades. With the improvement of the radiation therapy (RT) techniques, stereotactic body radiation therapy (SBRT) has been included in the management of metastatic disease. With the aim to evaluate the role of SBRT in patients with LM from STS we retrospectively review the medical records of the patients treated at our institution Material and Methods Patients were treated with SBRT if in good performance status (ECOG 1-2), unsuitable for surgical resection, with controlled primary tumor. The number of lung metastases for every patient was ⩽ 4. In a risk adaptive scheme, the dose prescription was: 30Gy/1fr, 60Gy/3fr, 60Gy/8fr and 48Gy/4fr. All treatments were delivered with Volumetric Modulated Arc Therapy (VMAT). A thoracic and abdominal CT scan was performed every 3 months after SBRT to assess the clinical outcome. Toxicity was reported according to Common Terminology Criteria for Adverse Events (CTCAE) scale version 4.0.