ESTRO 38 Abstract book

S1014 ESTRO 38

1 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Medical Physics Unit, Campobasso, Italy ; 2 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Radiation Oncology Unit, Campobasso, Italy ; 3 Department of Experimental- Diagnostic and Specialty Medicine - DIMES- University of Bologna- S. Orsola- Malpighi Hospital, Radiation Oncology Department, Bologna, Italy ; 4 Fondazione Policlinico Universitario A. Gemelli - Università Cattolica del Sacro Cuore, Radiation Oncology Department, Roma, Italy Purpose or Objective Treatment plans for high-risk prostate cancer are highly complex due to large irregular shaped target volumes, multiple dose prescription levels and several OARs close to the target. The quality of these plans is highly inter- planner dependent. We aimed to assess the performance of the Auto-Planning module present in the Pinnacle TPS (version 16.0), comparing automatically generated VMAT plans (AP) with the historically clinically accepted manually-generated ones (MP). Material and Methods Twelve consecutive patients treated with VMAT-SIB for high-risk prostate cancer were re-planned with the Auto- Planning engine. The PTV1 included the prostate and the seminal vesicles; the PTV2 included the pelvic lymph nodes. Both PTVs were simultaneously irradiated over 25 daily fractions at 65Gy (2.6 Gy/fraction) and 45Gy (1.8 Gy/fraction). All manually (MP) and automatically (AP) generated plans were created by means of the 'dual arc” feature. For the MP plans, additional non-anatomical structures needed to be delineated in order to interactively guide the optimization process. For AP plans, a progressive optimization algorithm is used to continually adjust initial targets/OARs objectives; tuning structures are automatically added during optimization to increase the dose fall-off outside targets. Various dose and dose- volume metrics (D98%, D95%, D50%, D2%, Dmean, V95% for target volumes; Dmean, Dmax and various Vx% for OARs), as well as conformity (CI) indexes and healthy-tissue integral dose (ID) were evaluated. A Wilcoxon paired test was performed for plan comparison with statistical significance set at p<0.05. Results Differences in all dose coverage metrics (in terms of V95%, D98%, D50%, D2% and Dmean) for both PTVs were not statistically significant (p<0.05). Differences in CI reached significance only for PTV2 (MP:1.59 vs. AP:1.48). Differences in DVHs were no significant in overall dose range for rectum, bladder and small bowel (rectum: V 50Gy : 31.7 vs. 32.2Gy, V 60Gy : 21.1 vs. 22.5Gy, Dmean: 40.6 vs. 40.5Gy; bladder: V 65Gy : 19.6 vs. 20.6, Dmean: 44.3 vs. 43.8Gy). For small bowel: V 15Gy : 105.0 vs 119.1cc, Dmean: 13.3 vs. 12.8cc. AP plans provided a decrease in Integral Dose of 5.1%. The mean number of MUs was not statistically different: MP (537) and AP (546), p=0.887. Conclusion The Pinnacle Auto-Planning module achieved highly consistent treatment plans in the cases of complex anatomical sites. The working time was substantially reduced with Auto-Planning. EP-1869 Automated VMAT planning in Pinnacle3: a dosimetric study in head-neck cancer S. Cilla 1 , A. Ianiro 1 , G. Macchia 2 , F. Romani 3 , A.L. Angelini 3 , M. Buwenge 4 , S. Cammelli 4 , V. Valentini 5 , A.G. Morganti 4 , F. Deodato 2 1 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Medical Physics Unit, Campobasso, Italy ; 2 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Radiation Oncology Unit, Campobasso, Italy ; 3 Department of Experimental- Diagnostic and Specialty Medicine - DIMES- University of Bologna- S. Orsola-

EP-1867 SBRT automatic treatment planning as a dose escalation strategy in pancreatic cancer S. Cilla 1 , A. Ianiro 1 , F. Deodato 2 , G. Macchia 2 , V. Picardi 2 , P. Viola 1 , M. Craus 1 , M. Buwenge 3 , S. Cammelli 3 , V. Valentini 4 , A.G. Morganti 3 1 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Medical Physics Unit, Campobasso, Italy ; 2 Fondazione di Ricerca e Cura "Giovanni Paolo II"- Università Cattolica del Sacro Cuore, Radiation Oncology Unit, Campobasso, Italy ; 3 Department of Experimental- Diagnostic and Specialty Medicine - DIMES- University of Bologna- S. Orsola- Malpighi Hospital, Radiology Oncology Department, Bologna, Italy ; 4 Fondazione Policlinico Universitario A. Gemelli - Università Cattolica del Sacro Cuore, Radiology Oncology Department, Roma, Italy Purpose or Objective Stereotactic body radiation therapy (SBRT) has been suggested as a new treatment strategy for locally advanced pancreatic cancer. However, the close proximity of highly radiosensitive organs prevent the administration of high doses to the vascular infiltration areas, aiming for a radical resection. Aim of this study was to perform a planning feasibility analysis of an automated planning system (Pinnacle 3 Autoplanning) using a VMAT-SIB technique as a dose escalation strategy. Material and Methods Twelve patients with unresectable pancreatic head adenocarcinoma due to vascular infiltration, were included in this study. CTVv was defined as involved vessels plus 5 mm or contact between the gross tumor volume (GTV) and vessels. The vascular PTV (PTVv) was obtained adding an anisotropic margin (5 mm craniocaudal direction, 3 mm in other directions). The tumor PTV (PTVt) was defined as the GTV plus an anisotropic margin (5 mm craniocaudal direction, 3 mm in other directions) and including the PTVv. A duodenum-PRV was defined by adding an isotropic 5 mm margin. SBRT was delivered in 5 fractions with a SIB strategy. For each patient 3 plans were optimized. Plan 1: 30 Gy (6 Gy/fraction) to PTVs; plan 2 and plan 3 escalated PTVv dose to 40Gy (8 Gy/fraction) and 50Gy (10 Gy/fraction), respectively. Corresponding EQD2 were 40Gy, 60Gy and 83.3Gy (a/b equal to 10). The dose-volume constraints for OARs were based on the AAPM TG101 recommendations. Automated plans were generated by Pinnacle Autoplanning module by means of VMAT dual-arc. A progressive optimization algorithm is used to continually adjust initial targets/OARs objectives while tuning structures are automatically added to increase the dose fall-off outside targets. The primary endpoint was to achieve PTVt and PTVv coverage in terms of D95%>95%, respecting all OARs constraints. Results OARs constraints were achieved in all patients. PTVv D95% was 30.8±0.1Gy, 36.1±5.4Gy and 39.2±12.0Gy at level 1, 2 and 3, respectively. In particular, the primary endpoint D95%> 95% was achieved in 12 patients (100%), 8 patients (67%) and 7 patients (58%) for level 1, 2 and 3, respectively. The mean dose to PTVv was 40.6±1.1 Gy and 49.7±2.3 Gy at level 2 and 3, respectively. PTVv mean dose was >90% in all patients. Conclusion Autoplanning reported a great potential for a tailored SBRT in advanced pancreatic cancer, allowing dose escalation and showing the feasibility to administer in all patients strongly differentiated doses. EP-1868 Automated VMAT planning in Pinnacle3: a dosimetric study in high-risk prostate cancer S. Cilla 1 , A. Ianiro 1 , P. Viola 1 , G. Macchia 2 , M. Buwenge 3 , A. Arcelli 3 , S. Cammelli 3 , V. Valentini 4 , A.G. Morganti 3 , F. Deodato 2