Radioimmunoguided surgery: clinical experience with different monoclonal antibodies and methods

The intraoperative detection of tumors by means of a gamma-ray detector that recognized radiolabelled monoclonal antibodies (MoAbs) on tumour cell surfaces has been shown to be feasible and clinically useful. The technology is called the Radioimmunoguided Surgery (RIGS) system. We have been working with this system for five years and in this paper we report our experience using different radiolabelled MoAbs and methods in terms of clinical utility in patients with primary or recurrent colorectal cancer. In the first part of the experience we injected with the MoAb B72.3 a group of 66 patients with primary (36) or recurrent (30) cancer introducing for 7 out of 66 a variation of the method to try to overcome some limits of the original procedure. With the new method, based on the avidin-biotin binding, it is possible to use anti-Cea MoAbs and to reduce the preoperative waiting time, injecting biotinylated MoAbs and avidin. In the second part of the experience, a second group of 15 patients with primary (12) and recurrent (3) cancer was injected with biotinylated MoAbs FO23C5 (anti-Cea) while in a third group of 16 patients, 6 with primary and 10 with recurrent cancer a cocktail of antibodies was used. During surgery a probe (NEOPROBE) was used to count obvious tumor, surrounding normal tissue and to scan the abdomen for areas of increased radioactivity. In the first group of patients tumour was localized by probe in 18/36 (50%) cases of primary cancer and in 24 out of 30 recurrences (80%). In the second group tumour was localized in 8/12 (67%) primary cancers and in 2 out of 3 (67%) recurrences. In the last group primary tumours were localized in 5/6 (83%) patients and recurrent cancer in 7/10 (70%). The method altered the surgical procedure in 2 out of 36 primary tumours (6%) and in 8 out of 30 recurrences (27%) injected with the B72.3. In the group of 15 patients injected with the anti-Cea the method changed the surgical strategy in 2/12 (16%) primaries and in 1 out of 3 recurrences. We had no real clinical utility in the primary cancers injected with cocktails but in 4 out of 10 (40%) patients with recurrent cancer it was possible to localize occult metastatic tissue. In conclusion, the sensitivity of the different MoAbs is similar in the groups even though it is noted that B72.3 seems to be more indicated in recurrent cancers and the FO23C5 in primary tumors.(ABSTRACT TRUNCATED AT 400 WORDS)