Combined use of 123I-labelled BCD-F9 and 4C4 monoclonal antibody with dissimilar specificity for breast cancer: implication for the detection limit of immunolymphoscintigraphy in the assessment of axillary lymph node metastases.

To determine whether the detection limit of immunolymphoscintigraphy (ILS), reported to be > or = 1 cm, can be improved by comparing imaging after administration of breast cancer-specific monoclonal antibody (MAb) BCD-F9 and breast cancer-nonspecific 4C4, 25 patients with suspected breast cancer were given injections of both 123I-labelled MAbs. The ILS was performed independently for both MAbs, the 4C4 scans serving as an ipsilateral negative control, and was used preoperatively to detect lymph node metastases. Twenty-one patients had breast cancer of whom 11 patients suffered from axillary involvement. Single interpretation of BCD-F9 scans gave true positive results in six of 11 and true negative results in 12 of 14 patients, whereas combined interpretation of BCD-F9 and 4C4 scans gave true positive results in nine of 11 and true negative results in 14 of 14 patients. On the basis of comparison of scintigrams of both MAbs, ILS allowed the detection of lymph node metastases 0.3-0.8 cm in diameter (n = 3). Immunohistochemistry of BCD-F9 and 4C4 MAbs of tumour-free and tumour-bearing lymph nodes correlated with ILS, with the exception of one patient. The study suggests that comparing scans obtained with BCD-F9 and 4C4 MAbs may improve the detection limit of ILS in the preoperative staging of axillae.