Novel intraoperative imaging technique may enhance precision of radical prostatectomies

A feasibility study showed that 68Ga-PSMA Cerenkov luminescence imaging (CLI), a novel operative imaging technique, demonstrated precision in assessing surgical margins during radical prostatectomy, according to findings published in the Journal of Nuclear Medicine.^1,2

68Ga-PSMA CLI showed the capacity to image the entire surface of an excised prostate specimen in order to identify prostate cancer tissue at the resection margin.

“Intraoperative radioguidance with CLI may help surgeons in the detection of extracapsular extension, positive surgical margins, and lymph node metastases with the aim of increasing surgical precision,” study author Christopher Darr, PhD, of the University Medical Center Essen in Essen in Germany, stated in a press release. “The intraoperative use of CLI would allow the examination of the entire prostate surface and provide the surgeon with real-time feedback on the resection margins.”

The study took place at a single site and included 10 patients with high-risk prostate cancer undergoing radical prostatectomy. The process involved 68Ga-PSMA PET/CT scans followed by radical prostatectomy involving intraoperative CLI of the excised prostate. For the first 2 patients, the investigators also incised and imaged the removed prostate gland to capture an image of the primary tumor itself.

Following the completion of surgery and imaging, the researchers compared postoperative histopathology with the tumor margin status on CLI. According to the researchers, “Measured CLI intensities were determined as tumor-to-background ratio.”

Post-surgery histopathology showed that 3 of 10 men had positive surgical margins (PSMs). CLI accurately detected 2 of 3 PSMs. Of 35 regions of interest, 25 (72%) “proved to visualize a tumor signal according to standard histopathology.” In these areas, the median tumor radiance was 11,301 photons/s/cm2/sr (range, 3328-25,428 photons/s/cm2/sr), and the median tumor-to-background ratio was 4.2 (range, 2.1-11.6).

The investigators also noted that, “False-positive signals were seen mainly at the prostate base, with prostate cancer cells overlaid by benign tissue. PSMA immunohistochemistry revealed strong PSMA staining of benign gland tissue, which impacts measured activities.”

In their conclusion, the authors wrote that to reduce false-positives, it is required to further optimize CLI protocol and/or use lower-energy imaging tracers, such as 18F-PSMA. The investigators plan to build on their initial research with a larger trial to evaluate diagnostic performance.

"Radical prostatectomy could achieve significantly higher accuracy and oncological safety, especially in patients with high-risk prostate cancer, through the intraoperative use of radioligands that specifically detect prostate cancer cells. In the future, a targeted resection of lymph node metastases could also be performed in this way. This new imaging combines urologists and nuclear medicine specialists in the local treatment of patients with prostate cancer," Boris A. Hadaschik, PhD, director of the Clinic for Urology of the University Medical Center Essen, stated in the press release.

Reference

1. Cerenkov Luminescence Imaging Accurately Identifies Surgical Margin Status During Radical Prostatectomy. Society of Nuclear Medicine & Molecular Imaging. Posted online October 6, 2020. https://bit.ly/3p2FEH2. Accessed November 5, 2020.

2. Darr C, Harke NN, Radtke JP, et al. Intraoperative 68Ga-PSMA Cerenkov Luminescence imaging for surgical margins in radical prostatectomy: a feasibility study. J Nucl Med. 2020;61(10):1500-1506. doi: 10.2967/jnumed.119.240424