KLK3 and neoplasm: The purpose of this pilot study was to demonstrate the early treatment response to radium-223 (223Ra)-chloride (Alpharadin, Algeta ASA, Oslo, Norway), a bone-seeking alpha emitter with a half-life of 11.4 days, using semi-quantitative 18F-fluoride PET and to compare with changes in biochemical markers including PSA as a tumour marker and ALP as a bone formation marker.