OA109] Validation of a radio-guided surgery technique based on beta-radiation: Test on ex-vivo specimens

Abstract

Purpose A very promising technique for radio-guided surgery (RGS) based on β -radiation is being developed. The lower background, with respect to the established approach with high penetrant γ radiation, can allow for a large diffusion of such a technique and extending the RGS to cases with a large uptake of surrounding healthy organs, such as abdominal and brain neoplastic disease or tumor of infancy. Methods To validate the β -RGS feasibility study, tests on ex-vivo specimens of brain meningioma and gastro-entero-pancreatic neuroendocrine tumors have been performed. These clinical cases were selected between the tumors known to express receptors to a β -emitting radio-tracer already in use in the clinical routine: 90Y-labelled DOTATOC. Voluntary patients were enrolled according to the standard uptake value (SUV) and the expected tumor-to-non-tumor ratios (TNR) estimated from PET/CT images after administration of 68 Ga-DOTATOC. All of them gave written informed consent to participate in the clinical trial, already approved by the Ethics Committee. After administration of a low activity (about 2.5 mCi) of 90Y-DOTATOC, the extracted ex-vivo specimens and the healthy tissue around the lesions were examined to assess the correlation between the counting rates measured by the developed β -detecting probe and the expected 90Y activity. Results All the neoplastic samples were correctly identified. A dependence of the counting rate both on the volume V and on the total activity of the sample were observed. Even injecting as low as 1.4 MBq/kg of radio-tracer, tumor remnants of 0.1 ml would be detectable in few seconds. Conclusions The results of the clinical tests showed the validity of the underlying assumptions and strengthening the feasibility studies already published. Small radiopharmaceutical activity is required to detect a tumor remnant as expected due to the low background rates. The negligible medical staff exposure was also confirmed.