68Ga-PSMA-11 Positron Emission Tomography/Computed Tomography for Primary Lymph Node Staging Before Radical Prostatectomy: Central Review of Imaging and Comparison with Histopathology of Extended Lymphadenectomy

Abstract

Background: Results from prospective trials have shown higher accuracy of prostate-specific membrane antigen (PSMA)-based positron emission tomography (PET)/computed tomography (CT) in detection of lymph node metastasis (LNM) compared to conventional imaging.

Objective: To evaluate the accuracy of ⁶⁸Ga-PSMA-11 PET/CT for LNM detection in patients undergoing radical prostatectomy (RP) and extended pelvic lymph node dissection (PLND).

Design, setting, and participants: Between June 2014 and November 2020, 96 patients with ⁶⁸Ga-PSMA PET/CT for primary staging underwent RP and extended PLND.

Outcome measurements and statistical analysis: The results from ⁶⁸Ga-PSMA PET/CT were compared with histologic data from primary PLND in 96 patients. All ⁶⁸Ga-PSMA PET/CT scans were centrally reviewed.

Results and limitations: Of 96 patients, 15.6% (n = 15) harbored LNMs. The median prostate-specific antigen at ⁶⁸Ga-PSMA PET/CT was 8.0 ng/ml (interquartile range 5.5-11.7). The majority of patients had intermediate- (52.1%) or high-risk disease (41.7%). Biopsy grade group 4 and 5 was present in 22.9% and 15.6%, respectively. The ⁶⁸Ga-PSMA PET/CT scans identified eight of 15 patients (53.3%) as LN-positive (true positive). The calculated per-patient sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ⁶⁸Ga-PSMA PET/CT in the detection of LNM were 53.3%, 98.8%, 88.9%, 92.0%, and 91.7%, respectively. The per-patient sensitivity and specificity in the detection of LNMs larger than 2 mm were 61.5% and 98.8%, respectively. The main limitation is the retrospective design of the study.

Conclusions: ⁶⁸Ga-PSMA PET/CT is accurate in lymph node staging and the results support its use for primary staging of prostate cancer.

Patient summary: We compared prostate-specific membrane antigen (PSMA)-based positron emission tomography (PET)/computed tomography (CT) findings with histopathology results after extended lymph node dissection and showed that it is accurate in detecting lymph node metastases. Our results support the use of PSMA PET/CT for primary staging of prostate cancer.

Keywords: Lymph nodes; Positron emission tomography/computed tomography; Primary staging; Prostate cancer; Prostate-specific membrane antigen; Staging.