Cancer research is searching for treatment strategies that inhibit a specific "overactive" signal pathway or protein in the tumor. Thanks to such a targeted approach, the therapy is expected to be both highly effective and well-tolerated. Well-differentiated carcinoids are prone to such strategies as they carry so-called somatostatin receptors on the surface of the carcinoid cells. For the last 20 years, these somatostatin receptors have formed the basis for specifically targeted or tailored treatment modalities of neuroendocrine tumors.

Somatostatins have been available as effective drugs for more than 20 years. By binding to the somatostatin receptors located on carcinoid cells they inhibit both tumor growth and hormone release. To increase the effectiveness of somatostatins radioactive-labelled derivatives of somatostatins have been designed. For more than ten years radionuclide-labelled somatostatins have been used for the specific radiation therapy of carcinoid tumor cells.

Today 177-lutetium and 90-yttrium are used as radioactive elements. 177-Lutetium or 90-yttrium are bound to the somatostatin analog octreotide through so-called chelators. The resulting radioactive drug (90-Y-DOTATOC, 177-Lu-DOTATOC or 177-Lu-DOTATATE) is administered intravenously for internal radiation treatment. As soon as the radioactive drug is circulating in the blood of the patient, the octreotide recognizes all carcinoid tumor cells carrying somatostatin receptors and attaches the drug to these carcinoid cells. The radioactive particles within the drug kill the carcinoid tumor cells by emitting ß- and ?-radiation. PRRT is suitable for internal radiation treatment of all somatostatinreceptor-positive metastases including bone or even myocardial metastases of carcinoid tumors.

PRRT should, however, not be used in patients with impaired kidney function (raised levels of creatinine or urea), bone marrow depression (reduced numbers of red or white blood cells or platelets) nor in patients with poorly-differentiated (G3) neuroendocrine neoplasms. Controlled prospective trials comparing PRRT and drug treatment are missing. However these treatment modalities are not mutually exclusive; on the contrary they are often combined in the individual patient.

Explanation of abbreviations often used in nuclear medicine:

DOTA        = 1,4,7,10-tetra-aza-cyclododecane-1,4,7,10-tetraacetic acid
DOTATOC  = DOTA-phe1-tyr3-octreotide (DOTA-tyrosine conjugate with octreotide)
DOTANOC  = DOTA-naphthyl3-octreotide (DOTA-naphthyl-alanine conjugate with octreotide)
DOTATATE = DOTA-tyr3-thre8-octreotide (DOTA-threonine conjugate with octreotide)

Prof. Dr. med. Hans Scherübl


Center of Neuroendocrine Tumors
Prof. Dr. med. Hans Scherübl
Vivantes Klinikum Am Urban
Academic Teaching Hospital of Charité-University Medicine, Berlin
Dieffenbachstraße 1
10967 Berlin, Germany
Tel: + 49 30 130 225201
Fax: + 49 30 130 225205
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