ESTRO 36 Abstract Book

S91 ESTRO 36 _______________________________________________________________________________________________

Material and Methods Anthropomorphic plastic phantoms were made with each having a simulated tumor bed that can be visualized using both ultrasound and CT. In the control, arm, the tumor is identified using ultrasound and inserted under ultrasound guidance. A tissue-locking needle and US probe are equipped with a real-time EM tracker. Under US guidance, the localization needle is placed within the tumor bed, which provides a rigid reference. The cavity is then contoured on US, creating a model in a virtual view. An EM tracked needle guide is pointed at the tumor bed and the catheter needle is inserted through the guide into the tissue. Additional parallel catheters are planned on the virtual view based on the first insertion and implanted in the target. The guidance software is built on the 3D Slicer (www.slicer.org) and SlicerIGT (www.slicerigt.org) open source platforms. In these experiments, a total of 10-15 catheters were inserted in each of the six phantoms. The goal was to place each catheter within the tumor bed. Three phantoms had catheter needles inserted with ultrasound only, while the other three had catheters inserted with combined EM tracking and US guidance. All six insertions were conducted by the same operator and the placement of the catheters was determined with CT. Results Under US guidance only in the three phantoms, 17 out of 26 catheters passed through the tumor bed. The average mean spacing was 0.86 cm +/- 0.33 cm. Under combined EM tracking and US guidance, 35 out of 40 catheters passed through the tumor bed. The average mean spacing was 1.05 +/- 0.19 cm. Conclusion These phantom experiments verify that EM tracking can be used to target catheter needles to the tumor bed. Additional research is currently being performed to translate this technique to patient trials. OC-0179 Dosimetric impact of errors in HDR-iBT of the breast using a catheter tracking method M. Kellermeier 1 , B. Hofmann 1 , V. Strnad 1 , C. Bert 1 1 Universitätsklinikum Erlangen- Friedrich-Alexander- Universität Erlangen-Nürnberg, Department of Radiation Oncology, Erlangen, Germany Purpose or Objective Electromagnetic tracking (EMT) was used to measure the implant geometry in fractioned HDR interstitial brachytherapy (iBT) of the breast. Based on the tracking data the dosimetric impact of common clinical errors, e.g. as reported in the United States by the Nuclear Regulatory Commission, were assessed using treatment planning For tracking of implant catheters, 28 patients were accrued within an institutional review board-approved study. The geometry of interstitial single-leader catheters (median: 18 pcs) was tracked on the HDR treatment table directly after each of the treatment fraction (up to nine during five days). Tracking has been performed by manual insertion of a small EMT sensor into each of the catheters. The breathing motion was compensated by computing the center of mass from three additional EMT sensors on the breast. Taking the tracking-based catheter data, different errors (swaps and shifts of catheters, changing the tracking direction of catheters, i.e. tip-end swap) were simulated. For dose calculation, the dwell positions (DPs) were determined along the catheter traces and the dwell times were taken from the approved treatment plan. Common contour-independent QC like the dose non-uniformity ratio (DNR) were analyzed. For investigation of contour- dependent QC, like the coverage index (CI) of the PTV, the corresponding EMT-derived DPs were registered to the CT- quality criteria (QC). Material and Methods

Proffered Papers: Breast

OC-0177 Brachytherapy for the Palliation of Dysphagia Owing to Esophageal Cancer: A Systematic Review. L. Fuccio 1 , D. Mandolesi 1 , A. Farioli 1 , C. Hassan 2 , L. Frazzoni 1 , A. Guido 3 , F. Violante 1 , C. Pierantoni 1 , A. Galuppi 3 , F. Bazzoli 1 , A. Repici 4 , A. Morganti 3 1 S.Orsola-Malpighi University Hospital, Department of Medical and Surgical Sciences, Bologna, Italy 2 Nuovo Regina Margherita Hospital, Gastroenterology Unit, Rome, Italy 3 S.Orsola-Malpighi University Hospital, Radiation Oncology Unit, Bologna, Italy 4 Humanitas Research University Hospital, Endoscopy Unit, Rozzano MI, Italy Purpose or Objective The management of dysphagia owing to eso phageal cancer is challenging. Brachytherapy has been proposed as an alternative option to stent placement. We performed a systematic review to examine its efficacy and safety in the Prospective studies recruiting at least 20 patients with malignant dysphagia and published up to April 2016 were eligible. The dysphagia-free survival (DFS) and adverse event rates were pooled by means of a random effect Six studies for a total of 9 treatment arms (623 patients) were eligible for inclusion. After 1 month since treatment, the DFS rate was 86.9% [95%CI: 76.0%–93.3%]; after 3 months, it was 67.2% [95%CI: 56.1%–76.7%]; after 6 months, it was 47.4% [95%CI: 38.5%–56.5%]; after 9 months, it was 37.6% [95%CI:30.0%–45.9%]; and, finally, after 12 months, it was 29.4% [95%CI: 21.6%–38.7%]. The heterogeneity between studies was high at 1-, 3- and 6- month assessment; the values of I 2 were 86.3%, 80.0% and 57.8%, respectively. The meta-regression analysis showed total radiation dose and number of fractions as the only positively influencing factors. Severe adverse event rate was 22.6% (95%CI 19.4–26.3). The main reported adverse events were brachytherapy-related stenosis (12.2%) and fistula development (8.3%). Two cases (0.3%) of deaths were reported due to esophageal perforation. Conclusion Brachytherapy is a highly effective and relatively safe treatment option therefore its underuse is no longer justified. Further studies should investigate the optimal radiation dose and number of fractions able to achieve the highest DFS rates. OC-0178 Demonstration of Catheter Insertion Using Electromagnetic Guidance in Breast Brachytherapy H. Brastianos 1 , T. Vaughan 2 , A. Lasso 2 , M. Westerland 1 , J. Gooding 1 , T. Ungi 2 , G. Fichtinger 2 , C. Falkson 1 1 Queen's University Cancer Research Institute, Radiation Oncology, Kingston- Ontario, Canada 2 Queen's University, School of Computing, Kingston- Ontario, Canada Purpose or Objective Accelerated partial breast irradiation using multi-catheter interstitial brachytherapy may be used for early stage breast cancers. To ensure ideal dosimetry over the tumor bed, the catheters need to be placed in parallel with equal spacing. The breast is a deformable organ; thus, placing catheters in the correct position is challenging. To ensure adequate spacing and position, we will apply real-time electromagnetic guidance (EM) in combination with ultrasound (US) to optimize the catheter insertions. This study will discuss the use of electromagnetic tracking catheter with ultrasound to insert catheters in phantoms. resolution of dysphagia. Material and Methods model. Results