RADIOGUIDED SURGERY WITH 99mTc-EDDA/HYNIC-TOC ("TEKTROTYD") - FEASIBILITY AND PRACTICALITIES

Abstract

Radioguided surgery (RGS) for patients with gastroenteropancreatic neuroendocrine tumours (GEP-NETs) has been suggested as an intraoperative way to aid in discrimination between diseased and healthy tissue, but it is not currently widely adopted. A systematic literature review demonstrated that RGS following administration of radiolabelled somatostatin analogues (SSAs) enables surgeons to identify more tumours in the gastrointestinal tract, but there is less evidence of benefit when used to localise pancreatic tumours. Few published studies report patient follow-up and therefore benefits for patient outcome are less well demonstrated. Studies reported a variety of techniques, including a range of tracers, administered activities, and discrimination techniques for the identification of tumours. Imaging studies of a phantom filled with a solution of technetium-99m demonstrated that quantification with novel LEHRS collimators combined with a "step-and-shoot continuous" (S&SC) acquisition technique demonstrates non-inferiority to traditional step-and-shoot (S&S) acquisitions, but that the two techniques did not give the same results. Variation in sensitivity between the static and motion portions of the acquisition was also noted. Three patients with GEP-NETs were recruited and imaged at two and four hours after administration of approximately 740 MBq of 99mTc-Tektrotyd. Contemporaneous blood samples were also taken and the radioactive concentration assayed. The images were reconstructed with and without S&SC acquisitions, and SUVs calculated for a range of normal and tumour tissues including blood-pool. S&SC demonstrated statistically different results to S&S for a range of tissues, and SUV values were higher in tumours at 4 hours than at 2. Comparison of calculated SUVmax to published values demonstrates similar results. The calculated uptake values from the imaging studies were used in a calculation of the minimum administered activity which would result in detection of 95% of tumours by the locally used intraoperative gamma-probes. The calculated minimum retained activity at the time of surgery was approximately 270 MBq, requiring administration of 450 MBq at four-hours earlier. For patients scheduled for morning surgery, tracer administration the evening prior would require 1,800 MBq. The resulting effective dose to the patient is approximately 0.5 mSv per 100 MBq administered; assuming an average 4-hours per surgical procedure the effective dose to the surgeon has been estimated at 20 microSv per 100 MBq retained at the time of surgery. No extremity dose to the surgeon can be estimated. Further work is required to demonstrate whether RGS improves patient outcomes, to determine the most appropriate protocol, and to verify patient and staff radiation doses.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Peter Julyan (Supervisor)