Studies of breast cancer imaging with radiolabeled antibodies to carcinoembryonic antigen. Immunomedics Breast Cancer Study Group.
Multiple imaging methods are currently used to detect the presence, location, and extent of breast cancer, either at initial presentation or during follow-up. Even at initial diagnosis, more specific methods are needed to complement the high sensitivity of mammography in the detection and diagnosis of mammary carcinoma. Therefore, the current study evaluates the potential use of a new monoclonal antibody-based imaging agent, arcitumomab (CEA-Scan), which comprises an anti-carcinoembryonic antigen monoclonal antibody Fab' fragment labeled directly with technetium-99m, in the detection of primary, recurrent, or metastatic mammary cancer. A prospective, non-randomized, open-label, multicenter trial was conducted in 123 women 100 with primary breast cancer confirmed by histology or cytology, and 23 with a prior history and who were under evaluation for possible recurrence or metastasis. A 1-mg dose of arcitumomab labeled with 20-25 mCi Tc-99m was injected i.v., and planar images were acquired at 5-8 hr, as well as single-photon emission computed tomography. Additional planar scanning was performed optionally at 18-24 hr. The imaging studies were interpreted as positive if there was abnormal focal activity, and were correlated, wherever possible, with histopathology or conventional imaging tests. In 78 evaluable patients with primary breast carcinoma arcitumomab showed an imaging sensitivity and specificity of 82% and 88%, respectively, even detecting lesions < 1 cm in 61% of the cases. Among 58 patients evaluable for axillary node involvement, 30 were positive by histopathology, of which arcitumomab was correct in 19 with cancer (63% sensitivity) and in 25 of 28 without cancer (89% specificity). Among 88 primary operable patients, arcitumomab showed additional sites of focal uptake outside of the breasts and axillae in 10, or 11%. In a total of 19 breast cancer patients with known or suspected recurrence or metastatic disease, 13, or 68%, showed one or more focal sites of uptake, involving the typical sites of spread of mammary cancer. No significant adverse effects or induction of human antimouse antibodies were observed in these patients. Arcitumomab immunoscintigraphy is a simple, same-day, and safe new imaging modality for the detection of sites of breast cancer, including lesions < 1 cm, with a reasonably high rate of sensitivity and specificity. It may be used to complement mammography in the differentiation of malignant from benign disease.