Imaging of small cell carcinoma using 131I-labelled antibodies to vasopressin associated human neurophysin (VP-HNP)

Preliminary studies are reported on the use of 131I-labelled antibodies against vasopressin associated human neurophysin to image tumors in patients with small cell carcinoma of the lung (SCCL). The rabbit polyclonal antibodies used in these studies were affinity purified on columns of neurophysin-Sepharose. Patients were pre-screened for the presence of neurophysin producing tumors by plasma RIA. Six patients who screened positive received approximately 1 mCi/70 kg body weight of radioiodinated antibody preparation, and scintigraphy was subsequently performed at 24 h, 48 h, and 72 h using a subtraction technique based on simultaneous imaging with radiopharmaceutical agents labelled with technetium-99m. Tumor was clearly demonstrated at 72 h in all five patients who had measurable lesions at the time of study, while no positive image was noted for one patient in complete clinical remission. Since approximately 70% of all SCCL patients have neurophysin-producing tumors, our findings suggest that neurophysin antibodies may be effectively used to scan tumors in a majority of patients with SCCL.