ESTRO 38 Abstract book

S866 ESTRO 38

studies are needed to better define the use of arc therapy in this setting of patients. EP-1606 Stereotactic Ablative Radiotherapy for oligometastatic soft tissue sarcoma patients D. Greto 1 , M. Loi 1 , D. Pezzulla 1 , M. Lo Russo 1 , M.A. Teriaca 1 , V. Maragna 1 , S. Lucidi 1 , D.A. Campanacci 2 , G. Beltrami 2 , G. Scoccianti 2 , L. Livi 1 1 University of Florence-Azienda Ospedaliera Universitaria Careggi AOUC, Department of Biomedical- Experimental- and Clinical Sciences, Firenze, Italy ; 2 Azienda Ospedaliero Universitaria Careggi- University of Florence, Department of Orthopaedic Oncology and Reconstructive Surgery, Florence, Italy Purpose or Objective Stereotactic Body Radiotherapy (SBRT) is emerging as a novel treatment option in oligometastatic cancer patients (≤3 synchronous lesions), but it is unclear whether this treatment option could be applied to bone and soft tissue sarcoma due to theoretical intrinsic radioresistance. The aim of our study was to evaluate the effectiveness and safety of SBRT in oligometastatic sarcoma. Material and Methods We collected data from a consecutive cohort of oligometastatic sarcoma patients treated in our Institution. Toxicity, Local Control (LC) rates and prognostic role of clinical and treatment-related characteristics (primary tumor type and location, synchronous or metachronous onset, SBRT site, dose delivered expressed as Biologically Effective Dose [BED], use of concurrent systemic treatment) were assessed. Results Thirty-four consecutive patients, accounting for 56 metastases (including 38 lung, 16 bone and 2 lymph node metastases), were treated at our institution with SBRT. Eight (23.5%) patients had metastatic disease at diagnosis. Nine (26.5%) patients in treatment with chemotherapy for metastatic disease received associated SBRT in case of oligoprogression. Median follow-up from first SBRT was 10 months (range 1-112). Median number of metastases treated per radiation course was 2 (range 1-3). Median number of SBRT fractions was 4.5 (range:3-12). Median prescribed dose was 40 Gy (range: 25-54 Gy) and median BED was 75 Gy (range 48-151). LC at 6 months, 1 year and 2 years was 85.4% [CI95% 73.8-92.4], 82.3 [CI95% 69.1- 90.6], and 73.6% [CI95% 56.8-86.5] respectively. At statistical analysis, only trunk primary tumor identified patients with poorer LC (p=0.02). Fifteen patients received 2 courses of SBRT while 1 patient received 3 courses of SBRT. No acute or chronic grade ≥3 toxicity was observed in the treated site, only 2 patients experienced minor toxicity consisting of 1 acute grade 1 skin reaction and 1 grade 1 late fibrosis, respectively. Conclusion In patients with oligometastatic sarcoma, SBRT yields satisfying LC with minimal toxicity regardless of concurrent treatment, metastasis timing location, and dose schedule. Repeated SBRT is feasible and may be considered to extend disease-free interval. EP-1607 Preoperative Radiation Therapy and IORT in Retroperitoneal Soft Tissue Sarcomas. Long Term Outcome F. Navarria 1 , S. Basso 2 , E. Palazzari 1 , R. Innocente 3 , A. Lauretta 4 , F. Matrone 1 , G. Fanetti 1 , A. Revelant 1 , A. Buonadonna 5 , C. Belluco 2 , V. Canzonieri 6 , J. Polesel 7 , G. Bertola 2 , A. De Paoli 1 1 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Radiation Oncology, Aviano, Italy ; 2 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Surgical Oncology, Aviano, Italy ; 3 Centro di Riferimento Oncologico CRO - IRCCS- Aviano-Italy, Radiation Oncology, Aviano, Italy ; 4 Centro di Riferimento Oncologico CRO - IRCCS- Aviano-Italy, Surgical Oncology,

Aviano, Italy ; 5 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Medical Oncology, Aviano, Italy ; 6 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Pathology, Aviano, Italy ; 7 Centro di Riferimento Oncologico CRO - IRCCS- Aviano- Italy, Cancer Epidemiology, Aviano, Italy Purpose or Objective Local control in patients (pts) with RPS is still challenging. Local recurrence after gross total resection remain the major issue. To improve local control radiation therapy (RT) was used. Post-op RT was not successful due to limited dose-tolerance of surrounding normal structure. Pre-op RT and IORT, allowing dose-escalation to high risk areas after resection, could overcome such limitations. Their use has been evaluated at our Institution. Material and Methods Long-term outcome of a consecutive series of 93pts(M/F ratio 50/40, median age 60yrs range 24-81) treated with preop RT +/-IORT at our Institute, from February 1999 to December 2017, is reported. Three pts had R2 resection and were escluded from this analysis. Fifty-five had primary 35 had recurrent disease. Pre-op RT consisted of 45-50.4 Gy in 25-28 frs after through-cut biopsy or initial operation. Conformal 3D-RT was used to include the tumor with a 3-5 cm margin (PTV1) with 45 Gy, followed by a reduced volume with a 2 cm margin (PTV2) up to 50.4 Gy. Concurrent chemotherapy (CT) with 3 cycles of c.i. Ifosfamide (1 gr/mq for 14 days, q 4 wks) was given to 31pts From 2012, IMRT with 45Gy/25frs and a SIB up to 52.5 Gy to posterior area at high risk, was used to optimize RT program. Pre-op RT (± CT) was followed by surgical resection after 4-6 weeks. A IORT boost was given to high risk area, if applicable, with a dose ranging from 10-18 Gy based on the completeness of surgical margins. Median tumor size was 16 cm (3-33 cm) and the most common histotypes were Liposarcoma (55%) and Leiomiosarcoma (21%). Tumor grade was G1:28.8%, G2: 27.7% and G3: 43.5%. Results All pts completed the planned pre-op RT at the median dose of 50.4 Gy (range 45-52.5Gy). Tolerance to pre-op RT was acceptable with G3 toxicity (15%) only in pts who received concurrent CT. Surgical operation was performed in all 90 with complete gross total resection in all operated pts. IORT at the median dose of 12 Gy (10- 15Gy) was given to 79 of 90 resected pts. IORT was not given to 11 pts, in 3 because of wide complete resection and in 8pts for IORT technical reasons. At a median follow-up of 3.5 years (02-18 years) the cancer specific survival (CSS), LDFS and DFS were 57.1%, 54.6% and 41.1% respectively. Status of surgical margins, R0 vs R1, resulted of borderline significant for LDFS (71.4% vs 41.4% and 65% vs 37.3% at 5 and 10 yrs, respectively, p=0.047). In the subset of 11 no-IORT pts, no difference in LDFS was reported. Complications occurred in 2 pts (3%) who had bowel perforation after pre-op RT ± CT; 4 pts (10%) developed G2-3 IORT related neuropathy and 3 pts (3.3%) IORT uretheral injury. Conclusion Pre-op RT and IORT in RPS was feasible with an acceptable toxicity profile. This approach allows a favourable complete resection rate and long-term outcome in disease control and survival with low rate of complications. IORT allows dose escalation to high-risk areas and in pts with R0 resection yields excellent local tumor control. EP-1608 Results of an aggressive local strategy after R1 or R2 unplanned surgery for soft tissue sarcomas P. Paul 1 , M. Laurence 2 , V. Gualter 3 , R.C. Isabelle 4 , M. Pierre 3 , B. Jean Yves 4 , P. Patrice 3 , B. Mehdi 4 , K. Marie 5 , D. Armelle 4 , S. Marie Pierre 1 1 Centre Léon Bérard, Radiation Oncology, Lyon, France ;