Impact of intraprostatic PSMA maximum standardised uptake value following prostatectomy: a systematic review and meta-analysis

Prevalence and Medium-Term Outcomes of Patients with Biopsy-Proven Intermediate- to High-Risk Prostate Adenocarcinoma with Low Intraprostatic Uptake on [68Ga]Ga-PSMA-11 PET/CT in the proPSMA Study

The current prevalence of low intraprostatic uptake for staging prostate-specific membrane antigen (PSMA) PET ranges between 4.4% and 17% in retrospective studies. We aimed to define the prevalence and describe the outcomes of patients with low intraprostatic uptake on PSMA PET/CT in the prospective proPSMA study. Methods: We identified patients with an SUVmax of 4 or less on PSMA PET/CT in the proPSMA study. Patients were followed up until 42 mo after randomization. The PRIMARY score was evaluated by 3 nuclear medicine physicians, with the result determined by consensus. Treatment failure was defined as new metastatic disease, biochemical recurrence, or initiation of salvage therapy. Results: Ten of 302 (3.3%; 95% CI, 1.6%-6.0%) patients had low intraprostatic uptake on PSMA PET/CT and normal findings on conventional imaging (CT and whole-body bone scanning). The median age was 66 y (interquartile range, 60.5-70.3 y). International Society of Urological Pathologists biopsy grade group was 3 in 5 patients and 5 in 5 patients, with no atypical histology identified. The median prostate-specific antigen level was 5.1 ng/nL (interquartile range, 2.3-8.3 ng/nL). The median follow-up interval was 30 mo (interquartile range, 24-39 mo). Multiparametric MRI was performed on 5 patients, with Prostate Imaging-Reporting and Data System score 5 in 2 patients, 4 in 1 patient, and 2 in 2 patients. The PRIMARY score was positive in 5 of 10 (50%) patients. Five (50%), 4 (30%), and 2 (20%) of 10 patients received radical prostatectomy, definitive radiotherapy, and androgen deprivation therapy alone, respectively. Of the 9 (90%) patients who received definitive treatment, 1 (11%) experienced treatment failure at 18 mo after radical prostatectomy and received metastasis-directed therapy. Biochemical recurrence was nonevaluable in the single patient who received androgen deprivation therapy alone. At the 42-mo follow-up after randomization, 4 of 9 (44%) patients who received definitive therapy remained on trial-none of whom had evidence of treatment failure. No other patients had new metastatic disease or initiation of salvage therapy during follow-up. Conclusion: In the proPSMA trial, there was a low prevalence (3.3%) of low intraprostatic uptake on PSMA PET/CT in patients with biopsy-confirmed prostate cancer, and treatment failure was infrequent.

Evaluating extraprostatic extension of prostate cancer: pragmatic integration of MRI and PSMA-PET/CT

PURPOSE

To explore pragmatic approaches integrating MRI and PSMA-PET/CT for evaluating extraprostatic extension (EPE) of prostate cancer (PCa).

METHODS

Consecutive patients with newly-diagnosed PCa that underwent multiparametric MRI and PSMA-PET/CT, followed by radical prostatectomy in 2021-2024 were included. Imaging parameters assessed on both modalities were: size, length of capsular contact (LCC), Likert scales (MRI EPE grade/PSMA Likert scale), PI-RADS/PRIMARY scores, and SUVmax. Three pragmatic integrated approaches were tested: (1) Integration of Likert scales (positive if either or both MRI and PSMA-PET/CT were positive); (2) P score (framework combining PI-RADS + PRIMARY); and (3) combining MRI morphological information with PSMA-PET/CT functional information (upgrading suspicion of lesions with LCC below cutoff if SUVmax>12). Diagnostic performance was tested with receiver operating characteristic (ROC) curves and compared using DeLong and McNemar tests.

RESULTS

67 men (median age, 66 years) with EPE in 76.1% (51/67) were included. Area under ROC curves (AUC) were 0.61-0.82; MRI-based LCC yielded the highest AUC 0.82 (0.71-0.92) with cutoff of ≥ 1.7 cm. Integrated Likert scale (MRI EPE grade/PSMA Likert scale) showed sensitivity of 80.4% (41/51) and specificity of 31.3% (5/16). P score (PI-RADS/PRIMARY) demonstrated sensitivity of 31.3% (16/51) and specificity of 87.5% (14/16). Combining morphological MRI information with functional PSMA-PET/CT yielded sensitivity and specificity of 80.4% (41/51) and 81.2% (13/16), respectively, which demonstrated significantly higher sensitivity but non-significantly different specificity compared with MRI-based LCC alone (66.7% [34/51, p = 0.02] and 87.5% [14/16, p > 0.99]). This approach upgraded suspicion in 8 patients with LCC < 1.7 cm due to SUVmax>12 among which 87.5% (7/8) were corrected upgraded and had pathological EPE.

CONCLUSION

Several pragmatic approaches were explored for integrating MRI and PSMA-PET/CT to assess EPE in PCa. Combining morphological information from MRI and PSMA expression on PET/CT demonstrated good diagnostic performance and may be a simple pragmatic integrated method that can be used.