111-In Octreotide
the somatostatin neuro is a small cyclic peptide present in neurons and endocrine cells particularly in the brain, in peripheral neurons in the endocrine pancreas and gastrointestinal tract. The native somatostatin has a half-life very short (1-3 min.) And have therefore been developed with a therapeutic purpose, its synthetic analogues:
- L ' Octreotide acetate is available corresponds to one of the similar molecule 111In-[DTPA Dphe ] Octreotide ( Octreoscan ). This molecule binds specifically to somatostatin receptors particular affinity with the subtypes 2 and 5.
I somatostatin receptors have been identified in numerous source neuro endocrine cells and their presence with varying degrees of density has also been documented in some non-neuronal cells and endocrine . For these reasons could be visualized by octreotide scintigraphy tumors that originate from cell lines expressing receptors for somatostatin . The main indication for the execution of a 111In-[DTPA Dphe ] is represented by neuro endocrine tumors that show a high density of somatostatin receptors and can be easily viewed by scintigraphy. The examination is indicated for the location of the primary tumor and metastases may be present to diagnose recurrent disease or its progression, to monitor the effect of surgery, radiation, or of chemotherapy to predict response to therapy as a prognostic factor for selecting patients for radioiodine therapy with an analogue of somatostatin labeled a beta-emitting radionuclide such as' Yttrium -90.
Since the density of somatostatin receptors in neuroendocrine tumors is highly variable, the sensitivity of the technique in different isoptipi is very diverse. It may also be reduced if concomitant therapy with octreotide acetate. in the case of neuroendocrine tumor scintigraphy with 111In-[DTPA Dphe ] octreotide not a question of choice except in determining the concentration of somatostatin receptors present in the tissue. The molecule of 111In-[DTPA Dphe ] octreotide is rapidly cleared from the circulation, and in fact only 10 min . after administration, only 35% of is injected into the circulation, a figure that at 20 min . down to '1%. Elimination is mainly via the kidneys with approximately 50% of injected activity was recovered in urine after 6 hours and 85% after 24 hours of injection. Elimination is through the hepatobiliary system. Somatostatin receptors are expressed in many cells of different organs that appear normal during a 111In-[DTPA Dphe ] octreotide :
Since the density of somatostatin receptors in neuroendocrine tumors is highly variable, the sensitivity of the technique in different isoptipi is very diverse. It may also be reduced if concomitant therapy with octreotide acetate. in the case of neuroendocrine tumor scintigraphy with 111In-[DTPA Dphe ] octreotide not a question of choice except in determining the concentration of somatostatin receptors present in the tissue. The molecule of 111In-[DTPA Dphe ] octreotide is rapidly cleared from the circulation, and in fact only 10 min . after administration, only 35% of is injected into the circulation, a figure that at 20 min . down to '1%. Elimination is mainly via the kidneys with approximately 50% of injected activity was recovered in urine after 6 hours and 85% after 24 hours of injection. Elimination is through the hepatobiliary system. Somatostatin receptors are expressed in many cells of different organs that appear normal during a 111In-[DTPA Dphe ] octreotide :
- liver, spleen, pituitary, thyroid and kidney
- gallbladder intestinno , renal pelvis, ureter and bladder.
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