68Ga-PSMA PET/CT Imaging Predicting Intraprostatic Tumor Extent, Extracapsular Extension and Seminal Vesicle Invasion Prior to Radical Prostatectomy in Patients with Prostate Cancer

68Ga-labeled prostate-specific membrane antigen (PSMA) ligand positron emission tomography/computed tomography (PET/CT) has shown promising results in patients with biochemical recurrence after primary therapy for prostate cancer. In this study, we evaluated the usefulness of PSMA I&T (imaging and therapy) PET/CT prior to radical prostatectomy.

The study population consisted of 21 patients with prostate cancer who underwent 68Ga-PSMA I&T PET/CT before either open or laparoscopic radical prostatectomy. Intraprostatic tumor extent, extracapsular extension (ECE) and seminal vesicle invasion (SVI) were assessed on the PET/CT scans. Tracer uptake was quantified in terms of standardized uptake values (SUVs). Imaging findings were correlated with final whole-gland histopathology.

Of the 21 patients, two had T stage 2b disease, nine stage 2c, six stage 3a and four stage 3b. The median Gleason score was 7. The SUVmean of the primary tumors was 9.5 ± 8.8. SUVmean was higher in tumors with ECE than in organ-confined tumors (13.8 ± 11.0 vs. 5.6 ± 3.2, p = 0.029). Peak tracer uptake was significantly positively correlated with Gleason score (rs = 0.49, p = 0.025). Sensitivity, specificity, positive predictive value and negative predictive value were, respectively, 94.7%, 75.0%, 97.3% and 60.0% for tumor infiltration of an individual prostate lobe, 75.0%, 100.0%, 100.0% and 97.4% for SVI, and 90.0%, 90.9%, 90.0% and 90.9% for ECE, using an angulated contour of the prostate as the criterion. Tumor volume derived from 68Ga-PSMA I&T PET/CT was significantly correlated with preoperative prostate-specific antigen value (rp = 0.75, p < 0.001) and tumor volume on histopathology (rp = 0.45, p = 0.039).

68Ga-PSMA I&T PET/CT prior to radical prostatectomy can contribute to presurgical local staging of prostate cancer. In this pilot study, 68Ga-PSMA I&T PET/CT showed promising results for prediction of lobe infiltration, ECE and SVI.

Nuclear medicine and molecular imaging. 2017 Mar 07 [Epub]

Christoph-Alexander J von Klot, Axel S Merseburger, Alena Böker, Sebastian Schmuck, Tobias L Ross, Frank M Bengel, Markus A Kuczyk, Christoph Henkenberens, Hans Christiansen, Hans-Jürgen Wester, Wiebke Solass, Marcel Lafos, Thorsten Derlin

Department of Urology and Urological Oncology, Hannover Medical School, Hannover, Germany., Department of Urology, Campus Lübeck University Hospital Schleswig-Holstein, Lübeck, Germany., Department of Nuclear Medicine, Hannover Medical School, Hannover, Germany., Department of Radiation Oncology, Hannover Medical School, Hannover, Germany., Radiopharmaceutical Chemistry, Technical University Munich, Garching, Germany., Institute for Pathology, Hannover Medical School, Hannover, Germany.