The immunoscintigraphic use of Tc-99m-labelled monoclonal anti-CEA antibodies (BW 431/26) in patients with suspected primary, recurrent and metastatic breast cancer.

The discrepancy between serum CEA levels and CEA tissue expression in patients with breast cancer is well known. Whereas immunohistochemistry shows positive CEA expression in 70-90%, the serum CEA levels are often within the normal range. We performed immunoscintigraphy and SPECT with a Tc-99m labelled anti-CEA monoclonal antibody (MAb BW 431/26) in 46 women with suspected breast cancer or recurrence. The results of anti-CEA immunoscintigraphy, mammography, serum CEA levels and immunohistochemistry were evaluated according to the histology of the tumor. Histology verified breast cancer or recurrence (pT1 [n = 7], pT2 [n = 17], pT3 [n = 3], pT4 [n = 3]) in 30 out of 46 patients; benign breast disease such as fibrocystic disease, fibroadenoma, fatty necrosis or chronic mastitis was responsible for suspicious mammographic findings in 16 patients. Immuno-SPECT showed 25 true-positive, 5 false-negative, 11 true-negative and 5 false-positive findings (sensitivity 83%, specificity 69%). Anti-CEA immuno-SPECT of 2 patients with bone metastasis showed all lesions previously detected by bone scintigraphy to be CEA-expressing metastases. In contrast, serum CEA levels were slightly elevated in only 5 out of 30 patients with histologically verified breast cancer (sensitivity 17%). The results of immuno-histochemistry were surprising; tissue CEA expression could be demonstrated in only 5 patients with breast cancer. According to our experiences with this Tc-99m labelled anti-CEA MAb, immuno-SPECT is a suitable additional method for the diagnosis of breast cancer and especially of recurrence. Pre-operative serum CEA levels give no support for the differentiation between benign and malignant breast tumors.