A negative PSMA PET/CT does not exclude microscopic pelvic nodal disease

Design

Systematic review and diagnostic accuracy meta-analysis

Population

16 studies, 1,999 patients with intermediate- or high-risk prostate cancer and histological node staging

Primary outcome

Sensitivity and specificity for pelvic nodal metastasis

Effect

PSMA PET/CT sensitivity 54.6% (95% CI 43.7 to 65.1), specificity 92.7%; MRI sensitivity 33.0%, specificity 94.9%

This systematic review and meta-analysis pooled 16 studies (1,999 patients) of intermediate- and high-risk prostate cancer in which preoperative imaging was checked against histology from pelvic lymph node dissection. Fourteen studies assessed PSMA PET/CT and six assessed multiparametric MRI.

Pooled sensitivity for nodal metastasis was 54.6% (95% CI 43.7 to 65.1) for PSMA PET/CT and 33.0% (18.7 to 51.3) for MRI. Specificity was high for both: 92.7% and 94.9%. PSMA PET/CT appeared more sensitive, but the comparison is indirect, because the two tests were mostly studied in different patients.

The practical message for reporting is about the negative scan. PSMA PET/CT is good at confirming nodal disease it can see, but about half of histologically involved nodes were missed, mostly because micrometastases fall below its resolution. Reports and multidisciplinary discussions should not present a negative PSMA scan as proof of node-negative disease.

• Report a negative PSMA PET/CT as no PSMA-avid nodal disease, not as node-negative.
• Expect about half of histologically involved pelvic nodes to be missed by PSMA PET/CT in this pooled analysis.
• Treat a positive PSMA node as highly likely to be real, given specificity above 90%.
• Do not use MRI node size alone to stage the pelvis; its pooled sensitivity was about one in three.
• Leave the decision on pelvic node dissection to the multidisciplinary team rather than a negative scan.

Why it matters

PSMA PET is increasingly treated as definitive staging; for nodes, histology still finds what the scan misses.

Don't overread it

The PSMA versus MRI comparison is indirect; it does not establish how much more sensitive PSMA PET/CT is.

The statistics, in plain English

Sensitivity of 55% means about 45 of every 100 patients with nodal metastasis at surgery had a negative scan. The wide interval for MRI (19% to 51%) reflects only six studies. Specificity above 90% means few false positives.

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