Immunoscintigraphy in pancreas carcinoma: A model for critical evaluation of radiolabeled monoclonal antibodies by planar imaging and tomography (SPET)

The results of immunoscintigraphy (SPET 1-2 d p.i., planar 5-7 d p.i.) in 50 patients with pancreatic cancer disease using different monoclonal antibodies and 131-I as well as 111-In as label are reported and experiences critically discussed. The studies are considered a crucial model for the assessment of limitating factors and claims for improvement because of the special difficulties for radioimmunodetection in the upper abdominal region. The clinical value actually appears restricted to patients with suspicion of local recurrence or widespread intraabdominal metastasis and to patients elected for immunotherapy with MAb. The potential value of radiolabelled nonspecific immunoglobulins for the determination and subtraction of nontumor background activity is discussed as a compromise procedure until new antibodies with higher tumor uptake in absolute terms and relative to nontumor tissues may be developed. The reproducibility of immuno-SPET results has been found sufficient for the application in therapeutic trials with cytotoxic or radiolabelled MAb. A first experience with intratumoral injection of 131-I-MAb confirmed the possibility of studying individually the metabolization rate of MAb by a tumor or to deliver a huge radiation dose into a tumor with low nontumor burdens. (orig.)