Demonstration of safety and feasibility of hydrogel marking of the pancreas-duodenum interface for image-guided radiation therapy (IGRT) in a porcine model: Implications in IGRT for pancreatic cancer patients

Publication date: Available online 2 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Avani D. Rao, Eun Ji Shin, Sarah E. Beck, Caroline Garrett, Seong-Hun Kim, Nam Ju Lee, Eleni Liapi, John Wong, Joseph Herman, Amol Narang, Kai Ding
PurposeLimitations in cone beam computed tomography (CBCT) soft-tissue contrast prohibit clinicians from clearly identifying the dose-limiting proximal duodenum in unresectable pancreatic cancer patients treated with radiation therapy (RT). This study tests the feasibility and safety of injecting a high-contrast hydrogel marker at the head of the pancreas (HOP) and duodenum interface and assesses the marker visibility on CBCT to localize this important boundary during image-guided RT in a porcine model.Methods and MaterialsThis was a two-stage study. The feasibility/visibility stage evaluated the ability to place the hydrogel using endoscopic ultrasound-guidance on 8 swine (4 euthanized at post-injection day 8, 4 euthanized at post-injection day 22) and assessed the quality of visibility of the marked location on CBCT in the longer-surviving group. The risk assessment stage evaluated the toxicity of targeted intrapancreatic injections (3 swine) and intramural duodenal wall injections (3 swine) to assess toxicity of a misplaced hydrogel injection. All swine underwent post-mortem examination and histopathological studies.ResultsThe HOP-duodenum interface was successfully marked using hydrogel in 6 of the 8 swine. Histopathologic examination of the 6 successful hydrogel injections showed mild/minimal (4 cases) or moderate (2 cases) reactive inflammation isolated to the injection site. Of the 4 swine survived to 22 days, 3 demonstrated successful hydrogel placement at the HOP-duodenum interface, and this marked location was clearly visible for positional guidance on CBCT. There was no evidence of pancreatitis or duodenal toxicity in the swine undergoing targeted intrapancreatic or intramural duodenum injections for the risk assessment stage.ConclusionsWe demonstrate the feasibility and safety of injecting a hydrogel marker to highlight the HOP-duodenum interface that has acceptable visibility on CBCT. This technique, translated to humans, enables on-board visualization of this important boundary between the radiation target and dose-limiting, radiosensitive duodenum, facilitating efforts to safely deliver dose-escalated RT.

Teaser

This study presents the feasibility and safety of marking the pancreas and duodenum interface with a high-contrast hydrogel and demonstrates acceptable visibility of the marked location on cone beam computed tomography using a porcine model. Translation of this technique to the radiotherapy treatment of pancreatic cancer patients would enable on-board visualization of this important boundary between the radiation target and the dose-limiting duodenum, facilitating future efforts towards safe dose-escalation.


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