Can response to palliative treatment with radiopharmaceuticals be further enhanced?

Bone-seeking radiopharmaceuticals (RF) are an effective systemic pain-palliative treatment schedule in patients with disseminated bone disease. This treatment relies on selective uptake and prolonged retention of RF at sites of increased osteoblastic activity, while the potential toxicity of systemic administration is reduced by relatively selective tumour targeting. The main theoretic advantage of bone-targeted radionuclide treatment is that radiation can be delivered selectively to subclinical tumours and to metastases that are too small to be imaged and treated by surgical excision or local external beam radiotherapy. The distribution of radiation dose throughout a tumour is heterogeneous, whilst the rate of response depends upon the pre-treatment condition of the patient and other factors. To enhance the effect of treatment with RF on cancer cells, the following strategies have been investigated: Individualisation of the administered dose, higher-doses, earlier or repeated radionuclide treatment, the use of new RF, and the use of a mixture of different RF. Furthermore, external beam radiotherapy, biphosphonates or chemotherapeutic agents have been combined with RF and have scored significantly better treatment results referring to pain relief, bone disease progression, etc, without important side effects. The role of bone seeking RF can be extended beyond bone pain palliation, to a synergistic anti-tumour effect.