Abstract
Neuroendocrine tumors (NETs) include a spectrum of neoplasms characterized by histologic heterogeneity with significant clinical differences. Generally are well differentiated tumors but often present metastases at diagnosis. Conventional imaging techniques result insufficient in early diagnosis and therapy monitoring. Standardized morphological criteria to assess treatment response are inadequate in NETs, because of their biologic evolution and the cytostatic nature of new oncologic treatments. Functional imaging modalities have improved the understanding and diagnosis of NETs by the use of somatostatin analogue tracers labelled with radioisotopes. 111 In-Octreotide scintigraphy was considered the gold standard imaging modalities for NET detection with a diagnostic accuracy approximately of 90%. Actually 68 Ga-Dota-SST radiotracers (SSTRTs) PET/CT represent a superior imaging procedure with higher accuracy in detection of NET lesions as compared to morphological imaging procedures and somatostatin receptor scintigraphy. Additionally, the use of somatostatin analogue radiolabelled tracers offers the possibility to non-invasively evaluate the presence of somatostatin receptor expression on NET cells, with direct therapeutic implications. However, in the management of patients with NETs and in the evaluation of response to therapy the specialists
Highlights
Neuroendocrine neoplasms (NETs) are tumors with an incidence of approximately 5/100,000 per year
In the SHARP trial, only 2% of patients in the treated group demonstrated a partial response by RECIST despite improvement in overall survival. These findings suggest that tumor shrinkage may not predict poor outcome in patients treated with targeted therapies because tumors may respond to targeted therapy by undergoing necrosis or cystic changes without decreasing, and possibly even increasing, in size
The use of 68Ga-DOTA-TOC is limited to a better overall accuracy and provide valuable data regarding the pattern of expression of SST on target lesions, which represents a useful non-invasive modality for selecting patients for therapy with hot or cold somatostatin analogues
Summary
Neuroendocrine neoplasms (NETs) are tumors with an incidence of approximately 5/100,000 per year. In the management of NETs 68Ga-DOTA-conjugate peptides PET/CT is used to: localize primary tumours and detect sites of metastatic disease (staging) [49]; follow-up of patients with known disease, if at the first diagnosis the tumor showed SST receptor, to detect residual, recurrent or progressive disease (restaging) [31, 42,43]; determine SST receptor status (patients with SST receptor-positive tumors are more likely to respond to Octreotide therapy) [46]; select patients with metastatic disease for SST receptor radionuclide therapy (with 177Lu or 90YDOTA-peptides ) [46]; monitor the response to therapy (surgery, radiotherapy chemotherapy or SST receptor radionuclide therapy) [7].
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