Application of very low dose-rate brachytherapy in gastrointestinal cancer.

Abstract

201 Background: Despite treatment intensity escalation, the high local recurrence rate for esophageal cancer has frustrated clinicians for decades. Conventional High Dose Rate brachytherapy, particle therapies, and other sophisticated treatment methods are encouraging but often fiscally and/or biologically infeasible. Additionally, these technologies often burden patients with numerous hospital visits, decreasing patient quality of life. Very low dose-rate brachytherapy (vLDR), with sources emitting relatively low energy, can be more cost effective than conventional radiation treatments, particularly in underserved communities, and can replace many hospital visits with one procedure. The dose distribution advantages of vLDR are irrefutable, especially in regard to doses to other tissues. vLDR seeds are currently used regularly in the prostate and have been tested in several other anatomical sites with good safety results. In the present study, a radioactive(RA) stent platform was developed and tested to apply vLDR therapy to cancers of the gastrointestinal (GI) system. Methods: Monte Carlo simulations were used to guide design of a RA esophageal stent. A design was chosen that minimized surface dose variation while using commercially available RA seeds. RA stents loaded with 60 -125 Seed-in Carrier, GE Healthcare were endoscopically placed in the naïve esophagus of 3 Yucatan swine. Previously, mock treatments using dummy seeds were performed in three similar pigs. Stents were left in place for between 4 and 7 weeks and reaction of the mucosa was assessed macroscopically and histologically. Results: Porcine esophageal tissue received doses in the range of 132-160 Gy at the mucosal surface and 39-48 Gy at a distance of 5mm from the stent surface. Tissues were collected at 0, 1 and 10 weeks after stent removal. No macroscopic radiation damage was seen at autopsy and pathological analysis yielded no radiation-related damage in evaluable tissues. Conclusions: In this preliminary study, no local or systemic damage due to radiation was observed after treatment of normal esophageal tissue with a vLDR stent device. Ongoing research aims to determine dose tolerance in esophageal tissue and target application of vLDR in other locations in the GI tract.