Image-guided radiotherapy (IGRT) is currently the gold-standard for both curative and palliative radiotherapy for cancer. Traditionally, IGRT references to bone and the carina as surrogates for tumour location. Peri-tumour fiducials enable narrower treatment margins and subsequently less normal tissue exposure to radiotherapy. Commonly gastrointestinal fiducials require specialised endoscopic ultrasound equipment and staff. This study aimed to assess the success rate of liquid fiducial placement through standard gastroscopy injection for oesophageal and gastric tumour edge marking pre-IGRT.
Data from consecutive patients referred for fiducial placement pre-IGRT of gastric and oesophageal tumours between January 2013-2020 were retrospectively assessed. Inclusion criteria were patients with (1) management plan for radiotherapy for oesophageal or gastric cancer; and (2) referred to the Gastroenterology team for fiducial placement. Exclusion criteria were patients that did not have liquid fiducials inserted (e.g. deemed as unfit for endoscopic procedure) and patients that had surgery/no radiotherapy after fiducial placement. The endoscopic procedure aimed to insert four fiducials per patient (2 proximal and 2 distal to the tumour), each injection consisting of 0.2-0.5mL of a 1:1 mixture of iodized oil and n-butyl 2-cyanoacrylate. A 23-gauge injector was used for the injection.
50 patients underwent fiducial implantation within the study period. Data on whether fiducial-based IGRT (F-IGRT) was used instead of the standard IGRT (S-IGRT) was available for 17 patients. The median(IQR) age was 71.8(65.1-78.1) years, and half were male. 13 patients (76.5%) were able to have F-IGRT while 4 had S-IGRT. In three of the patients that received S-IGRT the implanted fiducials could not be localised at the cone-beam computer tomography (CBCT) immediately prior to the IGRT. There were no complications after endoscopic implantation of liquid fiducials in our cohort.
F-IGRT was feasible in over 70% of patients undergoing liquid fiducial placement through standard gastroscopy injection technique.