The PRIMARY Score: Using intra-prostatic PSMA PET/CT patterns to optimise prostate cancer diagnosis.

Abstract

BackgroundMulti-parametric magnetic resonance imaging (mpMRI) is validated for the diagnosis of clinically significant prostate cancer (csPCa). 68 Ga-PSMA -11 PET/CT (PSMA-PET/CT) combined with mpMRI has improved negative predictive value over mpMRI alone for csPCa. The aim of this post-hoc analysis of the PRIMARY study was to evaluate the clinical significance of patterns of intra-prostatic PSMA activity, proposing a 5-point PRIMARY score to optimise accuracy of PSMA-PET/CT for csPCa in a low prevalence population. MethodsThe PRIMARY trial is a prospective multi-centre phase II imaging trial that enrolled biopsy-naïve men with suspected PCa, no prior biopsy, recent mpMRI (6 months) and planned for prostate biopsy. 291 men underwent mpMRI, PSMA-PET/CT and systematic +/-targeted biopsy. The mpMRI was read separately using PI-RADS (V2).PSMA-PET/CT (pelvic only) was acquired a minimum 60 minutes post injection. PSMA-PET/CT was centrally read for pattern (diffuse transition zone (TZ), symmetrical central zone (CZ), focal TZ or peripheral zone (PZ), and intensity (SUVmax). In this post-hoc analysis, a 5-level PRIMARY score was assigned based on analysis of the central read: 1. No pattern, 2. Diffuse TZ or CZ (no focal), 3. Focal TZ, 4. Focal PZ or 5. SUVmax ≥ 12. Two further readers independently assigned a PRIMARY score to 118 scans for inter-rater agreement. Associations between PRIMARY score and csPCa (ISUP≥2) were evaluated. ResultsOf 291 men enrolled, 162 (56%) had csPCa. PRIMARY score-1 was present in 16% (47), score-2 in 19% (55), score-3 in 10% (29), score-4 in 40% (117) and score-5 in 15% (43). The proportion of patients with csPCa and PRIMARY score 1 to 5 was 8.5% (4/47), 27% (15/55), 38% (11/29), 76% (89/117) and 100% (43/43) respectively. Sensitivity, specificity, PPV and NPV for PRIMARY score 1,2 (low-risk patterns) vs PRIMARY score 3-5 (high-risk patterns) was 88%, 64%, 76% and 81%, compared to 83%, 53%, 69% and 72% for PI-RADS (2 vs 3-5) on mpMRI. The inter-rater agreements for PRIMARY score 1,2 vs. PRIMARY score 3-5 was 0.76 (CI: 0.64-0.88) and 0.64 (CI: 0.49-0.78). ConclusionA PRIMARY score incorporating intra-prostatic pattern and intensity on PSMA-PET/CT shows potential with high diagnostic accuracy for csPCa. Further validation is warranted prior to implementation.

PET Criteria by Cancer Type from Imaging Interpretation to Treatment Response Assessment: Beyond FDG PET Score

“…The specific patterns were described as follows: Pattern A, defined as diffuse transition zone (TZ) activity if centrally placed within the prostate, with no PSMA activity extending to the edge of the prostate margin; Pattern B, symmetrical central zone (CZ) activity with no PSMA activity extending to the prostate margin; Pattern C, focal TZ activity defined visually as more than twice background TZ activity; Pattern D, focal peripheral zone (PZ) activity. Table 7 shows the 5-point PRIMARY score classification [ 13 ].…”

Three-dimensional ultrasound integrating nomogram and the blood flow image for prostate cancer diagnosis and biopsy: A retrospective study

“…At present, prostate biopsy was still the gold standard for the diagnosis of PCa, but there was a certain rate of missed diagnosis in puncture biopsy, and there were also complications after puncture. Meissner and Louise et al (31,32)recently reported that among patients highly suspected of PCa in MPMRI and PSMA-PET, patients with strong uptake of PSMA and MRI positive could avoid definitive biopsy and directly conduct definitive treatment. Avoiding prostate biopsy before RP might be an effective choice.…”

“…Meissner and Louise et al. ( 31 , 32 )recently reported that among patients highly suspected of PCa in MPMRI and PSMA-PET, patients with strong uptake of PSMA and MRI positive could avoid definitive biopsy and directly conduct definitive treatment. Avoiding prostate biopsy before RP might be an effective choice.…”

Modern paradigms for prostate cancer detection and management

“…Future studies will determine whether biopsy may be safely omitted in men with high clinical suspicion of clinically significant prostate cancer with negative combined imaging 13 . Although PI‐RADS scoring has long been used for MRI, recent research has led to the development of a standardised reporting system for PSMA PET/CT, with research ongoing 32,33 . PSMA PET/CT may suit men unable to have mpMRI prostate due to metallic foreign bodies or implants, as localisation with PSMA PET/CT can assist lesion targeting at biopsy.…”

“… 13 Although PI‐RADS scoring has long been used for MRI, recent research has led to the development of a standardised reporting system for PSMA PET/CT, with research ongoing. 32 , 33 PSMA PET/CT may suit men unable to have mpMRI prostate due to metallic foreign bodies or implants, as localisation with PSMA PET/CT can assist lesion targeting at biopsy.…”