OGC SO06 - Novel Non-metallic Fiducial marker for Radiotherapy in Oesophageal Cancer

Abstract Background Early oesophageal tumours are technically difficult to delineate on the planning computed tomography (pCT) for Image Guided Radiotherapy (IGRT). We describe the use of a novel non-metallic fiducial marker for this purpose. Method Non-metallic fiducial marker (NFM) (BioXmark) was used in 17 patients from April 2021 to November 2022 for marking tumour site prior to radical or palliative radiotherapy. NFM was injected in the sub-mucosal plane using fluoroscopy under general anaesthesia, with the patient supine and using regular injection catheter and syringes. After the initial series, further modifications to the technique improved the injection and shortened operative time. These include left lateral positioning, an ultra-fine injection catheters and micro-dosing syringes. Feedback from the treating radiation oncologists was sought for all the patients. Results Injection was successful in all the patients. In the initial series before the modifications to the technique, often the marker was a larger than anticipated due to a combination of poor visibility when the patients were supine and use of larger bore injection catheters. Once the patient position was changed along with the changes in the injection catheters and the syringes, marking was very precise. Conclusion Previously used fiducial markers are gold based. While these were visible on pCTs, they are known to cause distortion along with being expensive and cumbersome to inject. In comparison, NFM is easy to inject without the artefacts seen with metallic markers. We refined the technique further by changing the patient’s position to left lateral which afforded a improved fluoroscopic visibility. Introducing finer injection catheters and micro-dosing syringes further led to usage of lesser volume and precise marking respectively. In summary we present a series of patients whose early oesophageal tumours were marked with a NFM aiding precise delivery of radiotherapy.