Immunoscintigraphy of colorectal carcinoma utilizing 111In-labeled monoclonal antibody conjugate CYT-103

111In-CYT-103 scanning in recurrent colorectal cancer--does it affect standard management?

PURPOSE

In a blinded fashion, radiolabeled B72.3 was investigated in operative cases of recurrent colorectal cancer to determine if diagnostic accuracy would be improved to ultimately maximize curability and minimize interventional morbidities.

METHODS

Study patients underwent conventional evaluation including history, physical examination, abdominal/pelvic computed tomographic scan (CT), colon examination, and carcinoembryonic antigen (CEA) determination, with select magnetic resonance imaging and ultrasonographic imaging as indicated. Murine monoclonal antibody B72.3 was labeled with indium-111 (111In-CYT-103 provided by Cytogen) and scans obtained at 48 hours and, selectively, at 72 and 96 hours. Unlike previous studies, the operating surgeon was blinded to 111In-CYT-103 abdominal scan results until surgical exploration was complete.

RESULTS

Of 15 study patients (10 male; 5 female), average age was 57 years, and average CEA was 10 ng/ml (with eight elevated CEA levels). A single patient did not undergo surgery because of presence of pulmonary metastases identified on CT scan but not identified on a 111In-CYT-103 scan. Laparotomies included resection and intraoperative radiation (10), resection alone (1), and biopsy only (3). CT and 111In-CYT-103 scans were compared with operative findings. CT scans had an accuracy and positive predictive value of 47 and 100 percent, respectively, whereas those of 111In-CYT-103 scan were 60 and 82 percent, respectively. Contribution of the scan to diagnosis and management was graded by the surgeon as no effect (67 percent), beneficial effect (13 percent), or negative effect (20 percent).

CONCLUSIONS

111In-CYT-103 was more accurate compared with CT scan, but when value of the scan was examined with respect to its potential contribution to patient management, it was beneficial in only 13 percent of patients. Further refinements may enhance the value of antibody imaging techniques.

Detection efficiency of colorectal carcinoma recurrence using technetium pertechnetate-anti-carcinoembryonic antigen monoclonal antibody BW 431/26

BACKGROUND

A new anti-carcinoembryonic antigen (CEA) antibody, BW 431/26 (Scintimun, Behring-Werke, Marburg, Germany), labeled with technetium pertechnetate (Tc-99m), is an intact immunoglobulin G1 monoclonal antibody that has been used to image colorectal cancer (CRC). This report is part of a prospective multicenter clinical trial initiated by the International Atomic Energy Agency to evaluate the role of this antibody in radioimmunoimaging of patients with suspected disease recurrence.

METHODS

A group of 31 consecutive patients underwent radioimmunoimaging with Tc-99m-BW 431/26 after resection of their primary CRC. Patient referral was based on either a persistent rise in serum CEA levels of unknown origin and/or questionable findings by other imaging studies. Whole-body planar scans and single photon emission computed tomography scans of selected body regions (e.g., chest, abdomen) were performed up to 24 hours after the intravenous antibody injection. Pathologic antibody concentration localizations by radioimmunoimaging were correlated with surgical, clinical, and other imaging modality findings to validate the accuracy of radioimmunoimaging in detecting CRC recurrence.

RESULTS

A total of 75 detected tumoral lesions was evaluated: 26 of 75 were of known origin (36%), and 49 of 75 were of unknown origin (65%). There were four true-negative lesions, one false-negative lesion, and no false-positive lesions; all others were true-positive lesions. Sensitivity was 96.8%, specificity 100%, and accuracy 98.6%. The study was easy to perform, without untoward side effects on patients after antibody administration.

CONCLUSIONS

Anti-CEA antibody radioimmunoimaging is a highly reliable diagnostic procedure in detecting CRC recurrence and is useful especially for the diagnosis of patients with rising CEA blood levels of unknown origin, thereby significantly affecting patient management. Radioimmunoimaging should become part of the diagnostic workup of patients suspected of having CRC recurrence.

Radio-immunotargeting in colorectal carcinoma

Colorectal cancer is one of the most frequently studied diseases for investigating cancer detection using radiolabelled monoclonal antibodies. From many clinical studies it has become clear that with radio-immunotargeting (RIT) it is possible to visualise approximately 70% of known sites of colorectal cancer and to find otherwise occult tumour deposits in approximately 10% of patients. The intra-operative use of a gamma detection probe increases the detection rate of clinical occult intra-abdominal tumour sites to 30-40%. However, this clinical experience has also disclosed the many difficulties and pitfalls connected with this technique, with respect to antibody-, tumour-, patient- and isotope-related factors. Upstaging or early disclosure of disseminated disease by RIT has not proven to be beneficial in terms of improved survival, but might be of use in the management of an individual patient. The laborious and costly RIT technique, difficult scan interpretation and the lack of proven survival benefit precludes its routine use in clinical practice. However, the promising results warrant further study to improve the technique, and to validate the clinical usefulness of radio-immunotargeting.

Staging and surgery for colorectal cancer

Staging of colorectal cancer has become increasingly important to select groups of patients for limited or more extensive surgery, and for adjuvant radiotherapy and chemotherapy. The main treatment is still surgery, but subgroups may benefit from adjuvant therapy, even accepting additional side effects. Accurate staging is necessary to define different treatment groups. A critical review is given of the present methods of clinicopathological staging.