RECEPTOR SCINTIGRAPHY OF NON-NEUROENDOCRINE CANCERS WITH IN-111 PENTETREOTIDE

Somatostatin receptors (SR) are surface markers characterizing not onl y APUDomas associated with neuroendocrine identities but also malignan cies without neuroendocrine expression. Recently, the somatostatin ana log pentetreotide was labeled with In-111 (OctreoScan 111, Mallinckrod t Medical BV, Petten, Holland) and introduced for the in vivo visualiz ation in man of SR-positive tissues, In the present report, SR-specifi c scintigraphy is evaluated as a clinical tool for tissue characteriza tion in correlation with histological and radiological examinations, S cintigraphy was focused and performed in cancer types without neuroend ocrine tissue expression such as brain (n=6) and breast tumors (n=9) a nd lymphomas (n=5). Scintigraphy was performed for comparison at 6 and 22 h after i.v. application of 111 MBq (3 mCi) of In-111-Pentetreotid e. In the breast cancer group, the primary tumor was visualized in all 9 women as well as in all 4 cases,vith palpable axillary lymph nodes. Three women with a negative axillary node scan and impalpable nodes h ad positive biopsy, In two cases, mediastinal lymph node involvement w as observed, So far the role of SR-positive breast cancer (BC) scans r emains unknown. It is tempting to speculate that in resected women who are histologically and scintigraphically SR positive, it might be of value in the early detection of symptom-free recurrences, High densiti es of SR were present within both meningiomas, the high-grade astrocyt oma and the craniopharyngioma. Differentiation of low- and high-grade astrocytomas could not be successfully achieved because both grades sh owed intense radioactivity uptake, even though high-grade tumors lack SR. The latter might be due to the damaged blood-brain barrier and the poor radioactivity washout observed in high-grade astrocytomas. All f ive lymphomas could be detected due to the presence of activated lymph ocytes and macrophages that express SR at a sufficient density, In con clusion, SR scintigraphy in non-neuroendocrine malignancies does not s eem to be reliable for an initial tumor staging but rather more suitab le for a tissue characterization and extremely useful for monitoring c hanges of SR expression after treatment.