What is the comparative performance of mpMRI versus PSMA PET/CT for localizing prostate cancer recurrence in the prostatectomy bed?

1. What the evidence says about mpMRI’s strengths

mpMRI offers superior soft‑tissue contrast and spatial resolution that make it particularly good at detecting small recurrences at the vesico‑urethral anastomosis and within the prostatic fossa, and radiology reviews characterize it as the test of choice for evaluating the prostatectomy bed because of those technical strengths and dedicated pelvic sequences ^{[1] [3]}.

2. What PSMA PET/CT adds and where it can miss

PSMA PET/CT delivers higher overall lesion‑positivity rates in biochemical recurrence and consistently outperforms conventional imaging for nodal and distant disease, making it powerful for whole‑body restaging and for uncovering occult metastatic sites that alter management ^{[2] [4]}. However, PSMA tracers can be limited for very local lesions because physiologic urinary excretion concentrates radiotracer near the bladder and prostatic fossa—an issue repeatedly shown to reduce PET detectability of recurrences close to the vesico‑urethral anastomosis ^{[5] [3]}.

3. Direct comparisons: roughly equal for local recurrence, PSMA better overall

Systematic reviews and head‑to‑head meta‑analyses report that positivity rates for detecting local recurrence are broadly comparable between PSMA PET/CT and mpMRI—meta‑analytic pooled local‑recurrence rates are similar even when PSMA outperforms mpMRI for overall biochemical recurrence detection and for nodal disease (pooled positivity for PSMA higher overall; local recurrence pooled rates ~0.37 vs 0.38 reported across studies) ^{[2] [6]}. Individual prospective and single‑institution studies vary: some find PSMA PET/MRI or hybrid approaches detect more lesions at low PSA, while others show mpMRI detects small anastomotic recurrences missed on early PET imaging ^{[7] [5]}.

4. Combined imaging and clinical implications

Multiple authors and reviews emphasize complementarity: combining mpMRI’s anatomic detail with PSMA PET’s functional sensitivity improves confidence in localization and staging, and concordant findings are strong indicators of true local recurrence—this combined approach can guide salvage radiotherapy planning and biopsy targeting more effectively than either test alone in selected cases ^{[8] [9] [3]}. Evidence and guideline commentary also note PSMA’s clinical value for staging and treatment planning, especially where exclusion of pelvic or distant disease would change management ^{[10] [4]}.

5. Caveats, heterogeneity, and agendas to watch

Study heterogeneity—different tracers (68Ga vs 18F variants), timing after injection, PSA levels, imaging protocols, and reference standards—limits simple conclusions and produces variable sensitivity/specificity across cohorts ^{[9] [11]}. Industry and specialty enthusiasm for PSMA (and newer radiotracers) is strong in recent reports and conference material, which risks overgeneralizing PET superiority beyond contexts where anatomic localization in the prostatic bed is paramount ^{[4] [10]}. Conversely, older PET tracers and early imaging timings understate PSMA’s performance in some series, explaining discordant single‑center results ^{[5] [7]}.

6. Practical takeaways for localization in the prostatectomy bed

When the clinical question is precise anatomic localization in the prostatectomy bed (e.g., to define salvage radiation target or to biopsy the vesico‑urethral anastomosis), mpMRI is often the first‑line modality because of superior resolution; when the goal includes comprehensive restaging or detection of nodal/distal disease that would change therapy, PSMA PET/CT (or PET/MRI) should be added—many centers now use both to exploit complementary strengths and reduce missed lesions ^{[1] [2] [3]}. Where evidence conflicts, differences often trace back to tracer choice, urinary excretion effects, PSA level at imaging, and whether hybrid PET/MRI techniques were used ^{[5] [7]}.