INTRAOPERATIVE LOCALIZATION OF NEUROENDOCRINE TUMORS WITH I-125 TYR(3)-OCTREOTIDE AND A HAND-HELD GAMMA-DETECTING PROBE

Background. This study evaluates a novel method of intraoperative loca lization of endocrine gastroenteropancreatic tumors with a hand-held g amma-detecting probe to detect in situ tumor binding of the radioiodin ated somatostatin analog I-125-TYR (3) -octreotide. Methods. Seven pat ients with biochemical and radiologic evidence of a specific endocrine tumor, one patient with biochemical evidence of gastrinoma but no tum or localized by conventional imaging techniques, and four patients wit h equivocal preoperative biochemical or radiologic study results but s uspected of harboring a neuroendocrine tumor underwent abdominal explo ration with Intraoperative injection of I-125-TYR (3) -octreotide, 298 +/- 63 muCi. A hand-held gamma-detecting probe was used during operat ion to determine whether gross tumor accumulated the radiolabeled anal og and occult tumor could be detected. Positive uptake was defined as tumor/background ratios exceeding 2:1. Results. The tumor in all seven patients with gross disease accumulated I-125-TYR(3)-octreotide. Occu lt tumor beyond that appreciated with preoperative imaging or by routi ne operative exploration was detected in a patient with carcinoid tumo r. In the patient with the occult gastrinoma the probe detected the le sion within the duodenal bulb before duodenotomy and also predicted wh at proved histologically to be positive peripancreatic adenopathy. The re was a single false-positive reading from the stomach in a patient w ith suspected carcinoid tumor in whom no tumor could be found grossly or histologically. A pancreatic mass that probed negative proved to be an adenocarcinoma of ductal origin. Conclusions. Tumor-specific pepti de-receptor binding can be detected in situ with I-125-TYR (3) -octreo tide and a hand-held gamma-detecting probe. This technique may facilit ate neuroendocrine tumor localization and operative cytoreduction.