Bone-seeking radiopharmaceuticals in skeletal malignancy: evolution, not revolution

Many advanced malignancies are complicated by skeletal metastases, with attendant pain and disability. External beam radiotherapy is still the most effective treatment for isolated lesions. Bone-seeking radiopharmaceuticals were perceived as a means of delivering radiation to multiple lesions simultaneously. A wide variety of radioisotopes have been used in this endeavor, with myelosuppression being the most significant potential adverse effect. Benefits of treatment are modest, including a transient improvement in pain control and perhaps prolongation of the treatment-free period. This is best demonstrated in prostate cancer with lower responses by skeletal metastases from breast and lung cancers. However, the treatment is yet to produce any improvement in patient survival. Experimental approaches to improve treatment efficacy include combination with cytotoxic therapy, and administration earlier in the course of the disease. Bone seeking radiopharmaceuticals have been used in treatment of advanced osteosarcoma in humans and canines and achieved effective palliation. The myelosuppressive effects of these agents have been exploited in patients with multiple myeloma to assist in attaining myeloablation prior to stem cell transplantation. Development of more potent non-radiolabelled bisphosphonates and recognition of their antitumour effect against several tumours has sparked a recrudescence of interest in their use for bone metastases. Set against these developments, the role of bone-seeking radiopharmaceuticals in skeletal metastases may need to be redefined