In a collaborative phase III trial reported in JAMA Oncology, Thomas A. Hope, MD, and colleagues found that gallium-68 prostate-specific membrane antigen–11 positron-emission tomography (Ga-68 PSMA-11 PET) had 40% sensitivity and 95% specificity in the detection of pelvic nodal metastases prior to radical prostatectomy and pelvic lymph node dissection in men with prostate cancer.
The study supported the December 2020 approval of Ga-68 PSMA-11 PET in this setting.
Thomas A. Hope, MD
The trial enrolled 764 patients with intermediate- to high-risk prostate cancer being considered for prostatectomy at the University of California, San Francisco, and the University of California, Los Angeles, between December 2015 and December 2019. Patients underwent imaging scans with 3 to 7 mCi of Ga-68 PSMA-11 PET.
The primary outcome measure was sensitivity and specificity for pelvic lymph node metastasis detection compared with histopathology on a per-patient basis using nodal region correlation. All scans were read centrally by three blinded independent readers, with a majority rule for positive or negative findings.
Among the 764 men who underwent one Ga-68 PSMA-11 PET scan for primary staging, 277 (36%) subsequently underwent prostatectomy with lymph node dissection.
Based on pathology findings, 75 (27%) of the 277 patients had pelvic nodal metastasis. On Ga-68 PSMA-11 PET, 40 (14%) of 277 had pelvic nodal metastases, 2 (1%) had extrapelvic nodal metastases, and 7 (3%) had bone metastases.
For pelvic nodal metastases, Ga-68 PSMA-11 PET had a sensitivity of 0.40 (95% confidence interval [CI] = 0.34–0.46) and specificity of 0.95 (95% CI = 0.92–0.97). The positive predictive value was 0.75 (95% CI = 0.70–0.80) and the negative predictive value was 0.81 (95% CI = 0.76–0.85).
Among the 487 men who did not undergo prostatectomy, 108 were lost to follow-up. Among the 379 with follow-up, 262 (69%) underwent radiotherapy, 82 (22%) received systemic therapy, 16 (4%) underwent active surveillance, and 19 (5%) received other treatments.
The investigators concluded, “This phase III diagnostic efficacy trial found that in men with intermediate- to high-risk prostate cancer who underwent radical prostatectomy and lymph node dissection, the sensitivity and specificity of Ga-68 PSMA-11 PET were 0.40 and 0.95, respectively. This academic collaboration is the largest known to date and formed the foundation of a new drug application for Ga-68 PSMA-11 PET.”
Dr. Hope, of the Department of Radiology and Biomedical Imaging, University of California, San Francisco, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was supported by the National Cancer Institute, Prostate Cancer Foundation, Society of Nuclear Medicine and Molecular Imaging, and others. For full disclosures of the study authors, visit jamanetwork.com.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.