PWE-088 UK Pilot Study of EUS Guided Fiducial Marker Placement for Image Guided Radiotherapy in Oesophageal Cancer: Initial Results of Feasibility and Radiotherapy Outcomes

Introduction Fiducial markers (FM) help in radiotherapy planning (RT) by improving target delineation and optimise image guided radiotherapy (IGRT) during RT delivery. It helps in reducing interfraction RT setup uncertainty and improving the accuracy of treatment delivery. So far there are no studies in the UK that examined this technique with use of FM in Oesophageal cancers. We are hereby reporting the findings of our UK pilot study of FM guided 3 D Conformal RT and IGRT. Aim To evaluate the clinical outcomes of endoscopic ultrasound guided insertion of fiducial markers to demarcate oesophageal cancer for IGRT for Lancashire and South Cumbria cancer network (LSCCN) patients. Methods Institutional research and ethics committee approval was obtained. Our charity Rosemere Cancer Foundation funded this Prospective non-randomised cohort study. Cook EchoTip Ultra EUS Needles 22-F TM preloaded with 4 gold fiducial markers were used. Each marker measured 10 mm in length and 0.25μ in diameter. Olympus TM linear EUS was used to initially stage the tumour, followed by insertion of FM at the inferior and superior margins of the tumour. All patients with Oesophageal Squamous cancers at LSCCN from January 2015 to January 2016 considered for chemoradiotherapy were assessed for FM assisted IGRT. Contraindications include non-traversable tumours and patients with Oesophageal stent in situ. Results In total, 13 patients had 47 FM inserted under EUS guidance. Immediate CXR visualisation of FM was seen in 43/49 (88%). EUS guided FM insertion was feasible in all patients, no adverse events reported. Only 11 patients were eventually fit to undergo radiotherapy, of which data was available on 8 patients who received Radical 3 D conformal RT with 50 Gy. Markers were visualised in 21/27 (75%) on CT planning and during IGRT at treatment delivery using cone-beam CTs. Migration of the FM was seen with 2 markers, close to the actual lesion (in 2 patients). FM derived gross tumour length (GTV) on planning CT was similar to endoscopic tumour length (7.4 cm vs 8 cm). Mean GTV volume was 40.09 cubic cm (range: 18.57–80.1). Mean GTV length was 7.4 cm (range: 3.75–11.3). Mean PTV volume was 252.07 cubic cm (range: 135.4–357.2). Mean V20 for Lung was 19.16% (range: 13.1–28.37). FM assisted significantly in RT planning for tumour delineation. Conclusion FM for oesophageal cancer is technically feasible, safe, significantly improves target delineation for radiotherapy with excellent visibility for IGRT and acceptable stability (7.4% migration rate). Our completed data comparing FM based IGRT with conventional IGRT will help further clarifying its routine use in RT for patients with squamous cell oesophageal cancers. Disclosure of Interest None Declared