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Intraoperative 68 Gallium-PSMA Cerenkov Luminescence Imaging for surgical margins in radical prostatectomy – a feasibility study

  • Christopher Darr 1,
  • Nina Harke 1,
  • Jan Philipp Radtke 1,
  • Leubet Yirga 1,
  • Claudia Kesch 1,
  • Maarten Grootendorst 2,
  • Wolfgang Fendler 1,
  • Pedro Fragoso Costa 1,
  • Christoph Rischpler 1,
  • Christine Praus 1,
  • Johannes Haubold 1,
  • Henning Reis 1,
  • Thomas Hager 1,
  • Ken Herrmann 1,
  • Ina Binse 1,
  • Boris Hadaschik 1
1 University Hopsital Essen, Germany 2 Clinical Research, Lightpoint Medical Ltd.

Publication: The journal of nuclear medicine, February 2020

Objective 

To assess the feasibility and accuracy of Cerenkov Luminescence Imaging (CLI) for assessment of surgical margins intraoperatively during radical prostatectomy (RPE). 

Methods 

A single centre feasibility study included 10 patients with high-risk primary prostate cancer (PC). 68Ga-PSMA PET/CT scans were performed followed by RPE and intraoperative CLI of the excised prostate. In addition to imaging the intact prostate, in the first two patients the prostate gland was incised and imaged with CLI to visualise the primary tumour. We compared the tumour margin status on CLI to postoperative histopathology. Measured CLI intensities were determined as tumour to background ratio (TBR). 

Results 

Tumour cells were successfully detected on the incised prostate CLI images as confirmed by histopathology. 3 of 10 men had histopathological positive surgical margins (PSMs), and 2 of 3 PSMs were accurately detected on CLI. Overall, 25 (72%) out of 35 regions of interest (ROIs) proved to visualize a tumour signal according to standard histopathology. The median tumour radiance in these areas was 11301 photons/s/cm2/sr (range 3328 – 25428 photons/s/cm2/sr) and median TBR was 4.2 (range 2.1 – 11.6). False positive signals were seen mainly at the prostate base with PC cells overlaid by benign tissue. PSMA-immunohistochemistry (PSMA-IHC) revealed strong PSMA staining of benign gland tissue, which impacts measured activities. 

Conclusion 

This feasibility showed that 68Ga-PSMA CLI is a new intraoperative imaging technique capable of imaging the entire specimen’s surface to detect PC tissue at the resection margin. Further optimisation of the CLI protocol, or the use of lower-energetic imaging tracers such as 18F-PSMA, are required to reduce false positives. A larger study will be performed to assess diagnostic performance.