Robot-Assisted PSMA-Radioguided Surgery to Assess Surgical Margins and Nodal Metastases in Prostate Cancer Patients: Report on Three Cases Using an Intraoperative PET-CT Specimen Imager - Beyond the Abstract
Confocal microscopy has been suggested as an alternative to provide an immediate evaluation of surgical margins. Nevertheless, this technique equally relies on the availability of uro-pathologists and can hardly provide a definitive answer on the status of all margins, being set on the scale of microns. As for nodal evaluation during pelvic lymph node dissection, the only solution is to wait for the pathological examination, which is sub-optimal, especially in cases where the surgeon must trace and remove nodes positive at PSMA PET/CT, in both primary and salvage setting. In these cases, a radioguided approach is preferable to guide the surgeon in the dissection while avoiding to leave positive nodes behind.
Recently, a mobile, high-resolution PET/CT specimen imager has been developed (AURA 10 specimen PET/CT imager, XEOS Medical NV, Belgium) to provide an immediate ex-vivo identification of PCa foci with 68Ga-PSMA uptake in surgically resected specimens. This device is already used by breast cancer surgeons for the intraoperative evaluation of surgical margins, to evaluate the radicality of their procedure, and to extend the resection when needed.
In our pilot study, we used the AURA 10 specimen imager in three cases of robot-assisted radical prostatectomy (RARP) and pelvic lymph node dissection (PLND), to evaluate nodal invasion immediately after lymph nodes removal, and surgical margins status by removing the prostate through a Pfannestiel incision before doing the urethro-vesical anastomosis. An intravenous injection of 68Ga-PSMA-11 (2 MBq/kg) was needed at the beginning of the surgery. In our first three cases, the intraoperative use of the specimen PET/CT imager was safe and did not significantly delay the procedure. PET/CT images provided by the specimen imager showed a clear, focal uptake in a metastatic node, and no uptake or diffuse, faint uptake in negative nodes (figure). All three patients had negative surgical margins at final pathological examination. Two of them were clearly identified by the specimen imager, whereas findings were inconclusive in one case where the tumour was extracapsular but did not involve the surgical margin.
Our video article shows the step-by-step procedure and provides detailed results of these three cases. We believe that the intraoperative use of a portable PET/CT imager might improve the quality of robot-assisted radical prostatectomies, especially in conservative cases where full nerve-sparing is performed to preserve sexual function. The same goes for lymph node dissection, where such a technology could be used for a targeted resection of PSMA-positive nodes, particularly in the salvage setting. Further studies are needed to validate these preliminary findings and to find the appropriate thresholds of PSMA uptake able to differentiate cancer from normal tissue.
Written by: Marco Oderda, MD, PhD, Assistant Professor, Department of Surgical Sciences, Urology Unit, AOU Città della Salute e della Scienza di Torino, Molinette Hospital, University of Turin, Italy
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