The non tumour uptake of (111)In-octreotide creates new clinical indications in benign diseases, but also in oncology.

The use of somatostatin (SS) analogues in humans takes advantage by the availability of many related chemical forms that can be used for receptor therapy and, after radiolabelling, for diagnostic imaging and radionuclide therapy. The first proposed radiocompound, yet clinically widely diffuse, has been (111)In-octreotide (OCT), followed by positron emission tomography (PET) and beta emitter tracers. The main field of clinical applications is in neuroendocrine tumours (NET), starting by the demonstration of SS receptors (SSR) on the majority of NET, particularly on gastroenteropancreatic (GEP) tumours. Uptake of SS analogues can also be due to a SSR expression on non malignant cells when activated, as lymphocytes, macrophages, fibroblasts , vascular cells. Because of this uptake clinical indications can be found also in active benign diseases, as Grave's ophthalmopathy, rheumatoid arthritis, histiocitosis, sarcoidosis, idiopatic pulmonary fibrosis. Moreover, these cells can also determine the OCT in vivo uptake in tumours non expressing in vitro SSR, as non-snall cell lung cancer (NSCLC). Because of a different kinetic respect to SCLC a differential histotype diagnosis could be obtained. Starting from this premise OCT can also allows radioguided surgery in tumours non expressing SSR. Finally a relevant clinical role can be defined in the a priori recruitment and as marker of therapeutic efficacy in all the therapeutic strategies utilizing SSR, both in malignant and benign diseases.