Multiple Effects of Somatostatin Analogs Verified in Three Cases of Metastasized Neuroendocrine Tumors of the Gastroenteropancreatic System

Abstract

In neuroendocrine tumors of the gastroenteropancreatic (GEP) system, radiolabeled analogs of somatostatin (SST) are useful to the surgeon in different phases of treatment: preoperatively, to identify the lesion with somato-statin receptor scintigraphy (SRS), intraoperatively for localization using a hand-held gamma probe, and postoperatively acting directly to eliminate any residual tumor cells. Additional features of these analogs that are of value in treating such GEP tumors include their antiproliferative potential, which is in the process of being verified, and, above all, their anti-secretory action, so effective in symptom control. In this study the authors, based on their own experience, evaluate the effectiveness of SST analogs in treating GEP endocrine tumors. Three patients with malignant GEP apudomas were studied. In case 1, an insulinoma, the patient underwent four surgical procedures for ablation of the pancreatic tumor and of hepatic and lymph node metastases in addition to local radiofrequency treatment and radiometabolic therapy. Case 2 was a carcinoid tumor of the small intestine with hepatic metastases, managed by ileal resection, local radiofrequency treatment and receptor-mediated radionuclide therapy. In case 3, a non-functioning pancreatic carcinoma with liver and lymph node metastases, the patient underwent four surgical procedures, hepatic chemoembolization, antiproliferative treatment using octreotide (OCT) and metabolic radionuclide therapy. In all three cases SRS proved highly sensitive in the early detection of even the smallest recurrences. There was uncertainty, however, regarding the effectiveness of therapy with radiolabeled SST analogs. Hepatic metastases from the carcinoid were completely unresponsive, but in the case of the insulinoma, the hepatic metastases showed necrosis following treatment, while lymph node metastases were unaffected. In the case of the non-functioning carcinoma, there was a correlation between treatment and a marked improvement in the patient's clinical condition, although the appearance of the lesions themselves remained unchanged. The antiproliferative effect of OCT in this case was nil. SRS proved highly accurate in detecting recurrences during follow-up. The merits of radiometabolic therapy, on the other hand, were unclear, a finding reported elsewhere in the literature, and in the only case treated by prolonged OCT treatment, no antiproliferative action was observed. The diagnostic usefulness of SRS was thus confirmed and it appears likely that radiolabeled analogs used intraoperatively for tumor localization will prove equally of value. The effectiveness of receptor-mediated radionuclide therapy is still in the process of being verified. Based on the expectation of analogs with an universal affinity for SST receptors (sst), it is reasonable to look forward to a significant increase in the efficacy of this type of therapy.