Re-186 Radiotherapeutical Agent for Bone Tumor Metastases and Bone Pain Palliation Radiotherapy

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In recent years, deficiency of Tc-bone imaging in oncology patients is lack of specificity on osteoclastic (bone destruction)(OC) or osteoblastic (bone formation) (OB) bone metastases differenciation. Uniqueness of pentavalent polynuclear Tc-complex of dimercaptosuccinic acid (Tc(V)-DMS) to accumulate in bone pathologies are of interest. In this project, studies on the osteotropic character at cellular level and in OC and OB animal models were performed. At cellular level, the great affinity of Tc(V)-DMS for the osteoclastic cells was demonstrated. Comparative studies with the well known bisphosphonate (BBP) agent, Tc HMDP, showed lack of affinity in any OC or OB cells. In the OC type of animal model, by the VX2 implant in rabbit, clear affinity of Tc(V)-DMS for the metastatic area demonstrated by SPECT studies, the ARG (186Re(V)-DMS, 186Re-HMSDP) and histological studies confirmed the radioactivity accumulation in areas abundant in OC. The Tc-HMDP showed lack of accumulation in the OC model, but this agent accumulated 10-1 5 times with higher avidity in bone injured rats (OB model), demonstrated by preliminary injection of tetracycline, a fluorescent agent to accumulate in recently formed injured bone, superimposed to the radioactive region. The distinctive Tc(V)-DMS accumulation in OC bone tumor indicated the potentiality of this agent in the differentiation of OC from OB metastases and its plausible use in radiotherapy and bone pain palliation.