99mTc-Octreotide is a radiopharmaceutical used in single-photon emission computed tomography (SPECT) imaging for the diagnosis of pathological lesions that overexpress somatostatin receptors. Somatostatin receptors are commonly found in neuroendocrine tumors, such as carcinoid tumors, gastrinomas, insulinomas, and others. By targeting these receptors, 99mTc-Octreotide can help localize and visualize these tumors, aiding in their diagnosis and management.
The radioactive isotope technetium-99m (99mTc) is attached to the synthetic peptide octreotide, which has a high affinity for somatostatin receptors. This allows for the specific binding of the radiopharmaceutical to the somatostatin receptors on the tumor cells, leading to the accumulation of radioactivity in the tumor site. The emitted gamma rays can then be detected by a gamma camera during SPECT imaging, providing detailed anatomical and functional information about the lesion.
Overall, 99mTc-Octreotide imaging is a valuable tool in the evaluation of neuroendocrine tumors and other somatostatin receptor-positive lesions, helping clinicians in staging, monitoring response to treatment, and guiding therapeutic decisions.
Description
99mTc-EDDA/HYNIC-[Phe1-Tyr3-Octreotide] (99mTc-Octreotide) sold under the name of 99mTc-Tektrotyd® is a generic SPECT imaging agent for the diagnosis of pathological lesions in which somatostatin receptors are over expressed.
Clinical applications
99mTc-Octreotide is indicated for the diagnosis of neuroendocrine tumors (GEP-NET), pituitary adenoma, pheochromocytoma, paraganglioma, neuroblastoma, ganglio- neurinoma and medullary thyroid carcinoma.
In fact, several other cancers over express somatostatin receptors and could benefit from this tracer, but the tracer has not obtained MA for these indications (breast cancer, melanoma, lymphomas, prostate cancer, NSCLC, sarcoma, RCC, thyroid carcinoma, astrocytoma including glioblastoma, meningioma and ovarian cancer).
Availability
99mTc-Octreotide has been developed and is sold by POLATOM. This product is also available from BRIT (TCK-54) and Pars Isotope (99mTc-Octreotide, Tck-pars-2300)
Competition
This tracer is mainly intended for the diagnostic of patients with NET. It is closely related to the use of the therapeutic equivalents such as 90Y- or 177Lu-Octreotide or Octreotate. 177Lu-Lutathera has been approved in 2018, but has also been used over the past 12 years in the frame of clinical trials or compassionate use and thousands of patients have been treated. As these radiotherapeutic molecules were initially produced on site at a local radiopharmacy, the same radiochemists were able to prepare associated imaging agents. Labeling any somatostatin analogue with 99mTc is an option, but using 68Ga analogue has more potential, while the 177Lu-analogues could be used directly as tracers at lower doses. Presently next to 177Lu-Lutathera (177Lu-DOTATATE), 177Lu-DOTATOC is under late clinical phase development. In 2013, it was shown that 18F-FDOPA could play an important role in the diagnosis of NET patients, but finally the analogues 68Ga-DOTATATE and 68Ga-DOTATOC became the more used diagnostic agents in PET when 177Lu-labeled somatostatin analogues are to be used. 99mTc-Octrotide remains an interesting alternative for sites having no access to PET scanners.
Comments
Treatment of NET patients with radiolabeled somatostatin analogues has been under development for a long time without real financial support from industry for several years. Only recently one company (AAA), immediately followed by two others (ITM and OctreoPharm) decided to invest more heavily in these products. Since end of 2017 68Ga-DOTATATE and 68Ga-DOTATOC and the therapeutic analogue 177Lu-DOTATATE (Lutathera) became available on the market. The introduction of this drug will definitely make 99mTc-Octreotide of much lower interest, except in countries with no access to the drug with MA. In fact, SPECT imaging agents are not useful for quantification and 99mTc-Tektrotyd, like 111In-Octreoscan will allow diagnosing patients but are not really useful in adapting the therapeutic dose with the radiolabeled therapeutic analogue. 99mTc- Octreotide may still have some opportunities to play an interesting role in NET diagnostic and therapy.