EUS-guided fiducial marker insertion for radiotherapy in advanced esophageal carcinoma: submucosal insertion may lead to less migration when compared to intratumoral insertion

Background The use of radiotherapy is frequently required in the treatment of locally advanced esophageal squamous cell carcinoma. However, the margins of the tumor are often difficult to ascertain on computed tomography. Thus, EUS-guided fiducial marker insertion can aid the localization of the margins of the tumor. However, the optimal technique of the procedure is still uncertain. Methods This was a retrospective study of all patients that received EUS-guided fiducial marker insertion between March 2015 and December 2018. All patients suffering from esophageal squamous cell carcinoma scheduled for radiotherapy underwent the procedure within one week of the scheduled appointment. Gold fiducial markers were inserted under EUS guidance either intratumorally or within the submucosa just proximal and distal to the tumor. Outcome parameters included tumor characteristics, early and late migration rates, and tumor response rates. Results During the study period, 40 patients were recruited. 10 fiducial markers were placed intratumorally and 30 markers were placed submucosally. When comparing fiducials that were placed in the submucosa versus intratumorally, significantly more fiducials had early (40% vs 0%, RR = 0.6, 95% CI 0.36, 1.00) and late migration (60% vs 0%, RR = 0.33, 95% CI 0.13, 0.84) in the intratumoral group. The submucosal group had significantly more patients intended for curative intent (96.7% vs 70%, RR = 0.34, 95%CI 0.003, 0.361) and more patients with partial and complete response. There was no difference between the gross tumor volume, the clinical target volume, and the total radiation dose. Conclusion In esophageal carcinomas planned for radiotherapy, fiducial markers placed in the submucosa may lead to less migration.