Clinical utility of external immunoscintigraphy with the IMMU-4 technetium-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 of a new antibody imaging agent, CEA-Scan (Immunomedics Inc, Morris Plains, NJ), in 210 presurgical patients with advanced recurrent or metastatic colorectal carcinomas. Methods: CEA-Scan, an anti-carcinoembryonic antigen (CEA) Fab' antibody fragment labeled with technetium-99m-pertechnetate (^99mTc), was injected intravenously (IV), and external scintigraphy was performed 2 to 5 and 18 to 24 hours later. Imaging with conventional diagnostic modalities (CDM) was also performed, and findings were confirmed by surgery and histology. Results: The sensitivity of CEA-Scan was superior to that of CDM in the extrahepatic abdomen (55% v 32%; P = .007) and pelvis (69% v 48%; 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 70%), potentially obviating the need for histologic confirmation when both tests are positive. Imaging accuracy also was significantly improved by adding CEA-Scan to CDM. In 88 patients with occult cancer, imaging 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 antimouse antibodies (HAMA) to CEA-Scan after a single injection, and none of 19 assessable patients after two injections. Conclusion: CEA-Scan affords high-quality, same-day imaging, uses an inexpensive and readily available radionuclide, adds clinically significant information in assessing extent and location of disease in colorectal cancer patients, and only rarely induces a HAMA response.