PENTAVALENT TC-99(M)-DMSA IMAGING IN PATIENTS WITH BONE METASTASES

Pentavalent Tc-99(m)-dimercaptosuccinic acid (Tc-99(m)-(V)DMSA) has an established role in imaging medullary thyroid carcinoma. There have b een case reports of uptake in bone metastases. Our aims were to compar e Tc-99(m)-(V)DMSA with Tc-99(m)-hydroxymethylene diphosphonate (Tc-99 (m)-HDP) in bone metastases, to assess its value in imaging of bone me tastases, and to assess the prospects of the P-emitting analogues Re-1 86/188-(V)DMSA as palliative agents for painful bone metastases. Ten p atients confirmed by a Tc-99(m)-HDP bone scan to have bone metastases secondary to carcinoma of the prostate, lung or breast were injected w ith Tc-99(m)-(V)DMSA (600 MBq). Whole-body scans acquired at 3 and 24 h were compared with the Tc-99(m)-HDP bone scans. Tc-99(m)-(V)DMSA sho wed high soft tissue background, kidney retention and avid uptake in m ost bone metastases: 86% of bone lesions identified on bone scans were detected with Tc-99(m)-(V)DMSA. The lesion-to-normal ratios were comp arable to or lower than those for Tc-99(m)-HDP at 3 h, but increased b y 24 h. Instances of abnormal uptake in liver, primary lung tumour, ly mph nodes and pleural effusion were observed. We conclude that Tc-99(m )-(V)DMSA is a tracer for bone metastases (with lower sensitivity than Tc-99(m)-HDP) and soft tissue tumours. If Re-186/188-(V)DMSA behave s imilarly, they may find use in therapy for soft tissue tumours and bon y metastases.