First Ex Vivo Results of β^--Radioguided Surgery in Small Intestine Neuroendocrine Tumors with ⁹⁰Y-DOTATOC

In neuroendocrine tumor (NET), complete surgery could better the prognosis. Radioguided surgery (RGS) with β^--radioisotopes is a novel approach focused on developing a new probe that, detecting electrons and operating with low background, provides a clearer delineation of the lesions with low radiation exposition for surgeons. As a first step to validate this procedure, ex vivo specimens of tumors expressing somatostatin receptors, as small intestine neuroendocrine tumor (SI-NET), were tested. SI-NET presents a high uptake of a beta-emitting radiotracer, ⁹⁰Y-DOTATOC. Five SI-NET patients were enrolled after performing a ⁶⁸Ga-DOTATOC positron emission tomography/computed tomography (CT) and a CT enterography; 24 h before surgery, they received 5 mCi of ⁹⁰Y-DOTATOC. Surgery was performed as routine. Tumors and surrounding tissue were sectioned in different samples and examined ex vivo with the beta-detecting probe. All the tumor samples showed high counts of radioactivity that was up to a factor of 18 times higher than the corresponding cutoff value, with a sensitivity of 96% and a specificity of 100%. These first ex vivo RGS tests showed that this probe can discriminate very effectively between tumor and healthy tissues by the administration of low activities of ⁹⁰Y-DOTATOC, allowing more precise surgery.