Uptake of indium-111-labeled human polyclonal immunoglobulin G in pancreatic cancer: In vivo and in vitro studies

Radiolabeled human non-specific polyclonal immunoglobulin G (HIG), is used for the diagnosis of inflammation/infection. Focal uptake of HIG in malignant lesions has also been reported. We investigated the diagnostic value of In-111-HIG in patients with known pancreatic cancer. Fourteen consecutive patients with histologically verified pancreatic cancer were included in this prospective study. Four of them had undergone potentially curative surgery for their primary cancer. Eight patients had liver metastases. Planar and SPECT images of the abdomen were performed after administration of In-111-HIG (74-92 MBq). Scintigraphic results were compared to conventional imaging by means of CT scanning. In addition, In-111-HIG uptake was investigated in a panel of four representative human pancreatic cancer cell lines. Primary pancreatic tumors were visualized by In-111-HIG in 6 out of 10 patients (sensitivity 60%), while 1 was false positive. In comparison, CT scanning was true positive in 9 out of 10 patients (sensitivity 90%), and no false positive. Visualization of liver lesions by means of In-111-HIG was possible in 6 out of 8 patients (sensitivity 75%), while 1 was false positive. In vitro studies revealed only minimal uptake of In-111-HIG into cells (about 3% of activity). Our data demonstrate that In-111-HIG is able to visualize pancreatic primary cancers as well as liver metastases. However, the minimal uptake into tumor cells, as shown in vitro, suggests non-specific tumor related inflammatory reactions, increased vascular permeability, release of indium from In-111-DTPA-labeled antibody and local retention to be responsible for visualization of the tumor site.