Treatment of Painful Bone Metastases in Hormone-Refractory Prostate Cancer with Zoledronic Acid and Samarium-153-Ethylenediaminetetramethylphosphonic Acid Combined

Bone-seeking radiopharmaceuticals and bisphosphonates may be indicated in patients with cancer with painful osseous metastases to palliate pain symptoms or to prevent skeletal-related events. Both pharmaceuticals may have an additive or even synergistic palliative effect. The combined use of bone-seeking radiopharmaceuticals and bisphosphonates is, however, controversial because of assumed competition between both phosphonate-compounds at the bone level. We report a case of hormone-refractory prostate cancer (HRPC) with multiple painful osseous metastases. The patient was treated with samarium-153-ethylenediaminetetramethylphosphonic acid (Sm-153-EDTMP; Quadramet (R), CIS bio International, Saclay, France) in combination with zoledronic acid (Zometa (R), Novartis, Stein, Switzerland). He was treated for 6 months with 4 weekly intervals of zoledronic acid in combination with 3 monthly intervals of Sm-153-EDTMP. No negative interaction was found, toxicity was low, and efficacy high. He experienced a total relief of pain, a significant decrease of prostate-specific antigen (PSA) and, surprisingly, a significant decrease of tumor burden.