INDIUM-111-PENTETREOTIDE UPTAKE IN ENDOCRINE TUMORS AND LYMPHOMA

The biodistribution of (111)ln-pentetreotide was assessed in patients with gastroenteropancreatic (GEP) neuroendocrine tumors or lymphoma an d in control patients and analyzed as a function of scanning time, pre sence or absence of tumor uptake, tumor typo and previous octreotide t reatment. Methods: Patients underwent imaging 4 and 24 hr after inject ion of approximately 200 MBq (111)ln-pentetreotide. The frequency oi o rgan visualization was assessed on planar views. Total organ and tumor uptake 1% injected dose [ID]) was determined using the geometric mean method and regional tissue uptake (% ID/100 ml) by semiquantitative S PECT. Results: Liver, spleen, kidneys and urinary bladder were visuali zed in all patients. Thyroid, bowel and pituitary were more often visu alized at 24 hr than at 4 hr. Activity in the gallbladder, breast, ure ters and ascites was only occasionally observed. Total liver, spleen a nd thyroid uptake was stable over time, whereas kidney activity decrea sed slightly. At 24 hr, regional uptake was threefold lower in the liv er than in the spleen or kidneys and was similar in the three groups. In patients with long-term octreotide therapy, a positive correlation was found between the duration of octreotide therapy and liver or sple en uptake. Total and regional tumor uptake showed high intraindividual and interindividual variations. Total tumor activity was stable over 24 hr in patients with GEP and decreased in those with lymphoma. The m ean regional tumor uptake was 10-fold lower in patients with lymphoma than in those with GEP. Cold octreotide injected 24 hr after tracer ad ministration did not result in any displacement of organ and tumor act ivity. Conclusion: Organ uptake seems not to be influenced by the pres ence of (111)ln-pentetreotide-positive lesions or by tumor type. Tumor uptake is highly variable among patients and clearly lower in patient s with lymphoma than in those with GEP. The widespread of uptake value s in tumors indicates that radiotherapy using radiolabeled somatostati n analogs may not be applicable to all patients with (111)ln-pentetreo tide-positive tumors.