Comparison of 99Tcm-labelled MDP and DMAD bone scanning agents in patients with advanced breast cancer.

The detection of focal pathology on a bone scan is dependent on the contrast between uptake in a lesion compared with the affinity of the scanning agent for the surrounding normal bone. Dimethyl-amino diphosphonate (DMAD) has a relatively low uptake in normal bone compared with methylene diphosphonate (MDP). We have compared the bone scan appearance with MDP and DMAD in 11 patients with multiple bone metastases from breast cancer. The median time between scans was 7 days (range 6 to 14). In two patients additional lesions were identified on the DMAD scan. No additional lesions were visible on the MDP scans. In five patients some lesions were visualized more clearly with DMAD and others with MDP. In six patients no differences were seen. Anatomical resolution was generally less clear with DMAD and precise anatomical localization was sometimes impossible. We have demonstrated superior lesion detection with DMAD. The clinical value of this for the detection of early relapse of disease in the skeleton requires further study.