Background: The purpose of nuclear medicine in the evaluation of colorectal carcinoma is to complete the current diagnostic protocol, by means of monoclonal antibodies (MoAb) against tumoral antigens labelled with radioactive isotopes and performing an immunoscintigraphy.
Patients and methods: Immunoscintigraphies have been performed to 143 patients with colorectal carcinoma. Group I: antiCEA MoAb 99mTc-BW 431/26 (72 patients with 74 lesions, 48 primary tumors and 26 recurrences); group II: antiTAT-72 MoAb 111In-CYT-103 (71 patients with 75 lesions, 28 primary tumors and 47 recurrences). All positive images, not corresponding to physiological distribution of MoAb, have been considered as pathological.
Results: The sensitivity in the diagnosis of primary tumors in group I was worse than in group II (54.2% vs 66.7%). If rectum tumors were excluded, the sensitivity increased to 80% and 85.7%, respectively. In the suspicion of recurrences, if only lesions confirmed at surgery were considered, the sensitivity was 75% in group I and 89.7% in group II. The immunoscintigraphy has been the only technique able to diagnose recurrences in 4/23 cases from group I and 14/32 from group II. In liver, considering as metastases only hot images, the sensitivity is very low in group I (44.4%) and null in group II. No relationship has been found between tumour markers levels and the immunoscintigraphic result.
Conclusions: Immunoscintigraphy is useful in patients with colorectal carcinoma, especially in the case of recurrences and it is a complementary technique to other diagnostic procedures.