68Ga-BPAMD: PET-imaging of bone metastases with a generator based positron emitter

Purpose: Bone metastases are a serious aggravation for patients suffering from cancer. Therefore, early recognition of bone metastases is of great interest for further treatment of patients. Bisphosphonates are widely used for scintigraphy of bone lesions with 99mTc. Using the 68Ge/68Ga generator together with a macroyclic bisphosphonate a comparable PET-tracer comes into focus. Procedures: The bisphosphonate DOTA-conjugated ligand BPAMD was labelled with 68Ga. [68Ga]BPAMD was evaluated in vitro concerning binding to hydroxyapatite and stability. The tracer's in vivo accumulation was determined on healthy rats and bone metastases bearing animals by μ-PET. Results: BPAMD was labelled efficiently with 68Ga after 10 min at 100 °C. [68Ga]BPAMD showed high in vitro stability within 3 h and high binding to hydroxyapatite. Consequently, μ-PET experiments revealed high accumulation of [68Ga]BPAMD in regions of pronounced remodelling activity like bone metastases. Conclusions: 68Ga BPAMD reveals great potential for diagnosis of bone metastases via PET/CT. The straight forward 68Ga-labelling could be transferred to a kit-preparation of a cyclotron-independent PET tracer instantaneously available in many clinical sites using the 68Ge/68Ga generator.