A Prostate-Specific Membrane Antigen PET-Based Approach for Improved Diagnosis of Prostate Cancer in Gleason Grade Group 1: A Multicenter Retrospective Study

Using a novel PSMA-PET and PSA-based model to enhance the diagnostic accuracy for clinically significant prostate cancer and avoid unnecessary biopsy in men with PI-RADS ≤ 3 MRI

INTRODUCTION

The diagnostic evaluation of men with suspected prostate cancer (PCa) yet inconclusive MRI (PI-RADS ≤ 3) presents a common clinical challenge. [68Ga]Ga-labelled prostate-specific membrane antigen ([68Ga]Ga-PSMA) positron emission tomography/computed tomography (PET/CT) has shown promise in identifying clinically significant PCa (csPCa). We aim to establish a diagnostic model incorporating PSMA-PET to enhance the diagnostic process of csPCa in PI-RADS ≤ 3 men.

MATERIALS AND METHODS

This study retrospective included 151 men with clinical suspicion of PCa and PI-RADS ≤ 3 MRI. All men underwent [68Ga]Ga-PSMA PET/CT scans and ultrasound/MRI/PET fusion-guided biopsies. csPCa was defined as Grade Group ≥ 2. PRIMARY-scores from PSMA-PET scans were evaluated. A diagnostic model incorporating PSMA-PET and prostate-specific antigen (PSA)-derived parameters was developed. The discriminative performance and clinical utility were compared with conventional methods. Internal validation was conducted using a fivefold cross-validation with 1000 iterations.

RESULTS

In this PI-RADS ≤ 3 cohort, areas-under-the-curve (AUCs) for detecting csPCa were 0.796 (95%CI, 0.738-0.853), 0.851 (95%CI, 0.783-0.918) and 0.806 (95%CI, 0.742-0.870) for PRIMARY-score, SUVmax and routine clinical PSMA-PET assessment, respectively. The diagnostic model comprising PRIMARY-score, SUVmax and serum free PSA/total PSA (fPSA/tPSA) achieved a significantly higher AUC of 0.906 (95%CI, 0.851-0.961) compared to strategies based on PRIMARY-score or SUVmax (P < 0.05) and markedly superior to conventional strategies typically based on PSA density (P < 0.001). The average fivefold cross-validated AUC with 1000 iterations was 0.878 (95%CI, 0.820-0.954). Theoretically, using a threshold of 21.6%, the model could have prevented 78% of unnecessary biopsies while missing only 7.8% of csPCa cases in this cohort.

CONCLUSIONS

A novel diagnostic model incorporating PSMA-PET derived metrics-PRIMARY-score and SUVmax-along with serum fPSA/tPSA, has been developed and validated. The integrated model may assist clinical decision-making with enhanced diagnostic accuracy over the individual conventional metrics. It has great potential to reduce unnecessary biopsies for men with PI-RADS ≤ 3 MRI results and warrants further prospective and external evaluations.

Which patients with negative PSMA-PET imaging can safely avoid biopsy for prostate cancer? a novel step towards PSMA-based biopsy-free strategy

PURPOSE

This study aimed to identify if a subset of men can safely avoid or delay prostate biopsy based on negative results of prostate-specific membrane antigen positron emission tomography (PSMA-PET).

MATERIALS AND METHODS

Among 341 consecutive cases in a prospective biopsy cohort (NCT05073653), 111 treatment-naïve men with negative PSMA-PET (PRIMARY-score 1/2) were included. All participants underwent PSMA-PET and histopathological examinations. Clinically significant prostate cancer (csPCa) was defined as Grade Group ≥ 2. Multivariate logistic regression was employed to identify predictors of non-csPCa. Receiver operating characteristic (ROC) analysis was performed to detect non-csPCa on prostate pathology. PSMA-postive patients were additionally reviewed to assess the imaging and pathological outcomes.

RESULTS

Younger age was identified as an independent predictor (P = 0.006) for the absence of csPCa. ROC analysis of csPCa revealed the largest areas under the curve of 0.77 (0.67-0.87) and 0.78 (0.68-0.88) for individual age in the entire PSMA-negative cohort and the MRI subset, respectively (both P < 0.001). The negative predictive value (NPV) of PSMA-PET for csPCa detection improved with a decreasing age, from 88% in all, to 98% in men aged under 65 yrs (98% vs. 88%, P = 0.021), and to 100% in men aged under 60 yrs (100% vs. 88%, P = 0.040). The NPV of PSMA-PET improved from 88 to 94% when combined with negative MRI, and to 100% in men with negative MRI and aged under 65 yrs. The prevalence was 57% for csPCa and 65% for PCa of any grade.

CONCLUSION

We preliminarily propose that omission or postponement of prostate biopsy should be considered for men under the age of 65 yrs with negative PSMA-PET scored as PRIMARY 1 or 2. Conversely, prostate biopsy might be considered in biopsy-naïve men aged 65 yrs or older with strong clinical suspicion of PCa, despite negative PSMA-PET. Further prospective and external evaluation is needed to prove the robustness of this novel strategy.