T. Maurer, G. Weirich, T. Weineisen, HP Wester, B. Frisch, A. Okur, H. Kübler, M. Schwaiger, J. Gschwend, M. Eiber Initial experience with PSMA-radioguided surgery in prostate cancer patients 3rd Meeting of the EAU Section of Urological Imaging, Lisbon, Portugal, 2014 (bib)
	With the advent of 68Ga-HBED-PSMA PET hybrid imaging techniques, even small and atypical localized metastatic lesions of prostate cancer can be visualized. However, these lesions might not be easy to localize intraoperatively. Thus, the aim of this feasibility study was to evaluate intraoperative detection of metastatic lesions using a gamma probe after injection of radioactive-labelled PSMA-ligands in correlation with postoperative histological findings. Methods. Five prostate cancer patients with evidence of oligometastatic primary or recurrent disease on 68Ga-HBED-PSMA PET hybrid imaging were included in this feasibility study. 24 hours before surgery, patients received an intravenous injection of an 111In-labelled PSMA-ligand. Intraoperatively, metastatic lesions were detected by a gamma probe with acoustic and visual feedback. Using the freehand SPECT technique, optical tracking of the gamma probe allowed augmenting the live video stream of the field of surgery with a reconstructed 3D image showing the position of the hotspots. Results of radioactive rating (positive vs. negative) in resected tissue were compared to findings of postoperative histological analysis. Results. Lesion declared radioactive-positive intraoperatively as well as positive measurements of resected tissue ex vivo by the gamma probe corresponded to metastatic prostate cancer lesions with a specificity of 100%. Detection of lesions as well as complete resection of even small metastatic lymph nodes was improved by the use of the gamma probe. Compared to preoperative 68Ga-HBED-PSMA PET hybrid imaging, the intraoperative use of the gamma probe detected all positive lesions and might even be more accurate due to reduced lesion-to-detector distance. Conclusion. In this feasibility study, PSMA-radioguided surgery proved to be of high value for intraoperative detection of even small metastatic lesions in prostate cancer patients. However, greater patient numbers including follow-up data are needed to determine its possible role in clinical routine.
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