PSMA-PET imaging may miss small pelvic nodal metastases in men with prostate cancer

A study recently published in JAMA Oncology found that 68Ga-PSMA-11 PET imaging may miss small pelvic nodal metastases in men with intermediate- to high-risk prostate cancer.1

“A PSMA PET scan negative for pelvic nodal metastasis does not indicate that a pelvic nodal dissection is not required,” wrote Thomas Hope, MD, of the University of California in San Francisco, and colleagues.

While pelvic nodal metastases detected at radical prostatectomy are associated with biochemical recurrence after prostatectomy, improved detection of metastatic disease is needed prior to definitive therapy.

This prospective phase 3 trial included 764 patients, median age 69, with intermediate- to high-risk prostate cancer considered for prostatectomy from December 2015 to December 2019. The primary end point was the sensitivity and specificity of 68Ga-PSMA-11 PET imaging for the detection of pelvic lymph nodes compared with histopathology on a per-patient basis. Each scan was read by three blinded independent readers.

Of the 764 men who underwent a 68Ga-PSMA-11 PET scan for primary staging, 277 (36%) underwent prostatectomy with lymph node dissection. Based on pathology reports, 75 of 277 men (27%) had pelvic nodal metastasis. For pelvic nodal, extra-pelvic nodal and bone metastatic disease, 68Ga-PSMA-11 PET results were positive in 40 of 277 (14%), two of 277 (1%), and seven of 277 (3%) of patients, respectively. The sensitivity and specificity for pelvic nodal metastases were 0.40 and 0.95, respectively, compared with histopathology.

“This study is the largest prospective study using PSMA PET at time of initial staging,” the authors said. The results of this study were used to support the recent U.S. Food and Drug Administration approval of 68Ga-PSMA-11 PET at initial staging.

In invited commentary, Joseph Osborne, MD, PhD, of Weill Cornell Medicine in New York, and colleagues wrote that the results are similar to those from the prior OSPREY trial evaluating PSMA PET diagnostic performance of 18F-DCFPyL.2 “There is a clear message from both trials: clinicians taking care of patients with high-risk prostate cancer being assessed for prostatectomy can use a positive PET scan as a true positive,” they wrote. “Whereas a negative scan cannot be used to exclude disease or inform nodal dissection (both studies had a diagnostic sensitivity near 40%).”

Osborne and colleagues added that the latest study “has provided a road map for how preintervention PSMA PET imaging will guide the appropriateness of radical prostatectomy for the referring urologists. As such, these results are practice changing for the nuclear medicine physicians, urologists and medical oncologists who will manage this cohort of patients.”

References

1. Hope TA, Eiber M, Armstrong WR, et al. Diagnostic accuracy of 68Ga-PSMA-11 PET for pelvic nodal metastasis detection prior to radical prostatectomy and pelvic lymph node dissection: a multicenter prospective phase 3 imaging trial [published online ahead of print September 16, 2021]. JAMA Oncol. doi: 10.1001/jamaoncol.2021.3771

2. Osborne JR, Bander NH, Tagawa ST, et al. Prostate-specific membrane antigen positron emission tomography and the new algorithm for patients with prostate cancer prior to prostatectomy [published online ahead of print September 16, 2021]. JAMA Oncol. doi: 10.1001/jamaoncol.2021.3762