A gallium-67 scintigraphy obtained for comparison showed a large gallium-avid mass in the mid abdomen (outline) that correlates with the lymphadenopathy seen on the CT (arrow). The scintigraphic appearance of this mass was essentially unchanged or slightly improved as compared with the previous study of October 1992, suggesting an indolent tumor. The remainder of the gallium-67 study was unremarkable; no other abnormality was demonstrated.
While brain tumors contain somatostatin receptors, the receptor content varies with the tumor type. Medulloblastomas, oligodendrogliomas, and differentiated astrocytomas display somatostatin receptors. High grade glioblastomas lack somatostatin receptors. Meningiomas that arise from the meninges, which does not express somatostatin receptors, do exhibit these receptors.
The third group of tumors harboring somatostatin receptors originates from the gastroenteropancreatic tissues. Both islet cell carcinoma and carcinoids contain a high density of homogeneously distributed somatostatin receptors.
A miscellaneous group of tumors exhibiting somatostatin receptors comprises breast and lung carcinoma. Fifteen percent of breast cancer have showed somatostatin receptors on their surface. Only the small cell lung cancer appears to contain somatostatin receptors. The lymphopoietic system may be a target for somatostatin. Somatostatin has been shown to inhibit lymphocyte proliferation as well as IgA synthesis. Specific receptors have been identified in peripheral lymphocytes. Subsequently these receptors were also found on both B and T cells isolated from the spleen and Peyer's patches, although these receptors have a low affinity with somatostatin.
For imaging, octreotide is labeled with 111-In by complexing it with DTPA. This tracer is mainly excreted by the kidneys and shows only minimal accumulation in the liver and biliary tree.
Reubi et al evaluated the somatostatin receptor's status in a variety of malignant lymphoma using in vitro autoradiography with 125-I-Tyr-3-Octreotide. Eleven of 12 low grade lymponomas were positive for somatostatin receptors, as were 8 of 8 for intermediate grade and 7 of 10 for high grade tumors. Low to moderate density of receptors was observed in all the samples, but the high grade lymphomas expressed a higher density of receptors. These receptors were preferentially located on the follicular cells.
Lymphoma SS-R in vitro --------------------------------------------- Low grade 11/12 (92%) Intermediate grade 8/8 (100%) High grade 7/10 (70%)
W.H. bakker, E.P. Krenning, W.A. Breenan and coll., In vivo use of a radioiodinated somatostatin analogue: dynamics, metabolism and binding somatostatin receptor-positive tumors in man. JNM 32: 1184-1189 June 1991.
S.W. Lamberts, E.P. Krenning, J.C. Reubi, The Role of somatostatin and its analogs in the diagnosis and treatment of tumors. Endocrine Reviews 12 (4): 450-482, 1991.
E.P. Krenning, W.H. Bakker, P.P.M. Kooil and coll. Somatostatin receptor scintigraphy with indium-111-DTPA-D-Phe-1-Octreotide in man: metabolism, dosimetry and comparison with iodine-123-Tyr-3-Octreotide. JNM 33: 652-658, 1992.
W.H. Bakker, E.P. Krenning, J.C. Reubi and coll. In vivo application if 111-In-DTPA-D-Phe-Octreotide for detection fo somatostatin receptors-positive tumors in rats. Life Sciences 49: 1593-1601, 1991.
P. Marbach, U. Briner, M. Lemaire and coll. From somatostatin to Sandostatin: pharmacodynamics and pharmacokinetics. Metabolism 41 (9), suppl 2: 7-10, 1992.
J.C. Reubi, R. Maurer, K. vonWerder and coll. Somatostatin receptors in human endocrine tumors. Cancer Research 47: 551-558, 1987.
J.C. Reubi, L.Kvols, E. Krenning and coll. Distribution of somatostatin receptors in normal and tumor tissue. Metabolism 39 (9) suppl 2: 78-81, 1990.
E.P. Krenning, D.J.Kwekkeboom, J.C.Reubi and coll. 111-In-Octreotide scintigraphy in oncology. Metabolism 41 (9) suppl 2: 83-86, 1992.
S. Larson. Editorial: Receptors on tumors studied with radionuclide scintigraphy. JNM 32: 1189-1191 June1991.
J. Anthony Parker, MD PhD, email@example.com