ESTRO 37 Abstract book

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ESTRO 37

Purpose or Objective Recent data suggest intensity-modulated radiation therapy (IMRT) may improve local control in extremity soft tissue sarcoma (STS) treatment after limb-sparing surgery comparing to brachytherapy or three-dimensional conformal radiation therapy (3DCRT). The purpose of this study is to compare simultaneous-integrated boost (SIB) IMRT and SIB volumetric arc therapy (VMAT) in optimizing planning target volume (PTV) coverage and minimizing dose to organs-at-risk (OAR). Material and Methods Sixteen patients undergoing post-operative radiotherapy for lower extremity STS were assessed between 2013 and 2017. For each patient, two SIB treatment plans were proposed, one VMAT plan with 2 partial arcs, and one IMRT sliding-window plan with 6-8 tangential fields, in order to avoid the whole limb circumference. Both plans were optimized with a Photon Optimizer (PO) v13 algorithm, and calculated with Analytical Anisotropic Algorithm (AAA) v13. Treatments were evaluated using cumulative dose–volume histogram (DVH) data for OAR and PTVs. Prescribed dose was 66 Gy (2 Gy/fraction) for high-risk subclinical regions and 56 Gy (1.69 Gy/fraction) for lower-risk subclinical regions. PTV66 was defined adding 0.5-1 cm to CTV66 (tumor bed, surgical scar and margins: 1-2 cm longitudinal plane and 1.5 cm radially). PTV56 was defined adding 0.5-1 cm to CTV56 (tumor bed and margins: 4 cm longitudinal plane and 1.5 cm radially, including surgical tissues not covered in PTV66). OARs contoured were whole femur, neurovascular bundle, minimum skin corridor, normal tissue outside PTV56, joint and genitalia (testis in male and external genitalia in female). T-student test was performed for continuous related variables and SPSS 22.0 was used for statistical analyses. Results Eleven male (69%) and five female patients (31%) were included. The mean patient age was 60 years. The PTV of 7 patients (5 male, 2 female) extended into the pelvis. Both VMAT and IMRT showed very good target coverage, conformity (CI) and homogeneity index (HI). CI PTV66 was 0.98 (mean) ± 0.02 (standard deviation) (VMAT) vs 1.01 ± 0.04 (IMRT) (p<0.05). HI PTV66 was 0.09 ± 0.01 (VMAT) vs 0.08 ± 0.01 (IMRT) (p<0.05). IMRT delivered significantly lower skin corridor mean dose (10.4 Gy ± 6.8 Gy) compared to VMAT (14.7 ± 6.5 Gy) (p<0.05) (figure 1). There was a trend to a decrease in near-maximum absorbed dose (D2%) for all the OARs in VMAT plan, but both techniques showed comparable results (table 1).

brachytherapy (BRT) and adjuvant external radiation therapy (EBRT). Material and Methods Sixty patients presenting high grade recurrent STS of extremities or trunk treated with surgery and perioperative BRT followed by adjuvant EBRT +/- chemotherapy (CHT) were retrospectively analyzed. Local recurrences occurred after a median of 41.3 months after the first surgery (range: 5-268 months). Patient outcomes during FU as well as prognostic factors of patients outcome in terms of local control (LC), metastasis-free survival (MFS), disease-free survival (DFS) and overall survival (OS) were investigated. BRT delivered dose was 20 Gy (Low Dose-Rate or Pulsed Dose-Rate technique). EBRT was delivered with 3D-technique using multiple beams. The prescribed dose was 46 Gy to the planning target volume (PTV), delivered over 23 daily fractions. Neoadjuvant and adjuvant chemotherapy was used in patients with potentially chemosensitive histological subtypes. Univariate analysis was estimated according to Kaplan-Meier method and the log-rank test. Results Sixty patients (median age 53.5 years, range: 9-79), treated from January 2000 to January 2011 for high grade recurrent STS were included in this retrospective analysis. Median follow-up was 60.9 months (range: 15- 114), starting from the second surgery, performed for the late local recurrence. Thirteen patients out of 60 (21.7%) relapsed during FU, fifteen (25.0%) developed metastases and thirteen (21.7%) died. One-year LC, MFS, DFS and OS were 93.2%, 90.0%, 86.4% and 100.0%, respectively. 5- year LC, MFS, DFS and OS were 76.7%, 74.3%, 62.2% and 74.6%. An improved 5-year DFS was recorded in patients with lower arm versus upper arm and trunk tumors: 82.2% versus 53.8% and 66.7%, respectively; p: 0.034. The worse results recorded in upper limb STS may depend on the greater difficulty of radical surgery in this dimensionally smaller and richer of neurovascular bundles district. Patients not receiving CHT showed an higher 5- year MFS, DFS and OS (p: 0.055, 0.091 and 0.070, respectively); no statistical difference according to histology was detected. Conclusion The combination of BRT and EBRT is able to obtain satisfactory results and should therefore be taken into consideration in the case of recurrent tumors, to ensure a greater local control compared to surgery alone. Prospective studies on combination treatment modalities in the adjuvant treatment of relapsing STS are still necessary to improve these results. EP-1629 Are SIB-VMAT and SIB-IMRT good techniques for extremity soft tissue sarcoma radiotherapy treatment? I. Ortiz González 1 , D. Morera 2 , L. Valencia 1 , P. Mateos 3 , R. Roncero 1 , M. Vidal 1 , N. Aymar 1 , J. Gadea 1 , J.C. Font 2 , J. Pardo 1,4,5 1 Hospital Universitari Son Espases, Radiation Oncology, Palma de Mallorca, Spain 2 Hospital Universitari Son Espases, Medical Physics, Palma de Mallorca, Spain 3 Grupo Juaneda, Radiation Oncology, Ibiza, Spain 4 Hospital General de Catalunya, Quironsalud, Sant Cugat del Vallès, Spain 5 Institut d’Investigació Sanitaria de Illes Balears, IdisBa, Balearic Islands, Spain