Pentavalent 99Tcm-DMSA imaging in patients with bone metastases

Pentavalent 99Tcm-dimercaptosuccinic acid (99Tcm-(V)DMSA) has an established role in imaging medullary thyroid carcinoma. There have been case reports of uptake in bone metastases. Our aims were to compare 99Tcm-(V)DMSA with 99Tcm-hydroxymethylene diphosphonate (99Tcm-HDP) in bone metastases, to assess its value in imaging of bone metastases, and to assess the prospects of the beta-emitting analogues 186/188Re-(V)DMSA as palliative agents for painful bone metastases. Ten patients confirmed by a 99Tcm-HDP bone scan to have bone metastases secondary to carcinoma of the prostate, lung or breast were injected with 99Tcm-(V)DMSA (600 MBq). Whole-body scans acquired at 3 and 24 h were compared with the 99Tcm-HDP bone scans. 99Tcm-(V)DMSA showed high soft tissue background, kidney retention and avid uptake in most bone metastases: 86% of bone lesions identified on bone scans were detected with 99Tcm-(V)DMSA. The lesion-to-normal ratios were comparable to or lower than those for 99Tcm-HDP at 3 h, but increased by 24 h. Instances of abnormal uptake in liver, primary lung tumour, lymph nodes and pleural effusion were observed. We conclude that 99Tcm-(V)DMSA is a tracer for bone metastases (with lower sensitivity than 99Tcm-HDP) and soft tissue tumours. If 186/188Re-(V)DMSA behave similarly, they may find use in therapy for soft tissue tumours and bony metastases.