CLINICAL UTILITY OF EXTERNAL IMMUNOSCINTIGRAPHY WITH THE IMMU-4 TC-99M FAB' ANTIBODY FRAGMENT IN PATIENTS UNDERGOING SURGERY FOR CARCINOMA OF THE COLON AND RECTUM - RESULTS OF A PIVOTAL, PHASE-III TRIAL

Purpose: To assess the performance and the potential clinical impact o f a new antibody imaging agent, CPA-Scan (Immunomedics Inc, Morris Pla ins, NJ), in 210 presurgical patients with advanced recurrent or metas tatic colorectal carcinomas. Methods: CEA-Scan, an anti-carcinoembryon ic antigen (CEA) Fab' antibody fragment labeled with technetium-99m-pe rtechnetate (Tc-99m), was injected intravenously (IV), and external sc intigraphy was performed 2 to 5 and 18 to 24 hours later. Imaging with conventional diagnostic modalities (CDM) was also performed, and find ings were confirmed by surgery and histology. Results: The sensitivity of CEA-Scan was superior to that of CDM in the extrahepatic abdomen ( 55% v32%; P=.007) and pelvis (69% v48%; P=.005), and CEA-Scan findings complemented those of CDM in the liver. Among 122 patients with known disease, the positive predictive value was significantly higher when both modalities were positive (98%) compared with each alone (68% to 7 0%), potentially obviating the need for histologic confirmation when b oth tests are positive. Imaging accuracy also was significantly improv ed by adding CPA-Scan to CDM. In 88 patients with occult cancer, imagi ng accuracy was enhanced significantly by CEA-Scan combined with CDM ( 61% v 33%). Potential clinical benefit from CEA-Scan was demonstrated in 89 of 210 patients. Only two patients developed human anti-mouse an tibodies (HAMA) to CPA-Scan after a single injection, and none of 19 a ssessable patients after two injections. Conclusion: CEA-Scan affords high-quality, same-day imaging, uses an inexpensive and readily availa ble raodionuclide, adds clinically significant information in assessin g extent and location of disease in colorectal cancer patients,. and o nly rarely induces a HAMA response. (C) 1996 by American Society of Cl inical Oncology.