PSMA-targeted imaging of prostate cancer: evolution of a success story

relapse at low PSA values <1 ng ml−1, the obtained detection rates of 99mTc-labeled PSMA-SPECT/CT are lower than those reported by 68Ga-PSMA PET/CT imaging.1 This is in line with our experiences in early recurrent prostate cancer patients and low PSA values investigated with PSMA tracers for SPECT/CT imaging.3 Although very useful for PSMA-radioguided surgery,4,5 111 In-labeled PSMA I&T (or 99mTc-labeled PSMA I&S)-based SPECT/CT detects only less than half of the metastatic lesions that are identified by previous 68Ga-PSMA PET/CT. This is among other reasons just merely related to the different sensitivity and imaging resolution of SPECT versus PET systems. Therefore, it can be expected that also SPECT/CT with 99mTc-labeled HYNIC-Glu-Urea-A will not be able to reliably identify recurrent disease at these very low PSA values. Still, the authors have to be congratulated for their initial report on 99mTc-labeled PSMA-SPECT/CT and are very much encouraged to further pursue this novel imaging technique.