Abstract
P362
Introduction: 68Ga-prostate-specific membrane antigen positron emission tomography/computed tomography (68Ga-PSMA PET/CT) is promising in biopsy-free radical prostatectomy (RP). However, PSMA expression in benign prostatic hyperplasia (BPH) tissue and related positive reaction are concerns, inadequate specific or positive predictive value of imaging diagnosis strategy could become the Achilles’ Heel of biopsy-free RP. This retrospective study was conducted to investigate BPH-related false positive rate of 68Ga-PSMA PET/CT in detecting prostate cancer (PCa) and the influence of maximum standardized uptake value (SUVmax) on biopsy-free RP.
Methods: Patients who received 68Ga-PSMA PET/CT because of clinical suspicion of PCa based on elevated prostate-specific antigen (PSA) (>4ng/ml) or abnormal digital rectal examination and subsequently were confirmed to be BPH or PCa by systematic biopsy or/and targeted biopsy between April 2020 and January 2022 were primarily considered eligible for the study. The 68Ga-PSMA PET/CT fusion images were interpreted using a five-point Likert scale. All cases with a PET score of 1 or 2 were classified as negative, while those with a PET score of 3, 4, or 5 were categorized as positive. For the positive patient, the SUVmax value of the dominant lesion on PET was recorded for further analysis. The highest SUVmax in the prostate gland was also collected for negative cases with low-level radiotracer uptake. Prostate biopsy tissues were examined using immunohistochemistry staining to determine PSMA expression. The Spearman rank correlation analysis was performed to estimate the correlation between the SUVmax and ISUP grade group. The receiver operating characteristic (ROC) curve was generated for SUVmax values, from which the area under the curve (AUC) and the Youden index was calculated. Sensitivity and specificity were calculated based on the cutoffs.
Results: 89 BPH patients and 94 PCa patients were included. 27 of the 89 BPH cases were considered 68Ga-PSMA PET/CT-positive, and all dominant lesions were confirmed to be BPH tissue through the targeted biopsy and, thus, were regarded as BPH-related false positive (30.3%). To explore the efficacy of SUVmax in discriminating positive BPH from PCa and its influence on biopsy-free RP, the SUVmax values between positive BPH and PCa patients with different ISUP grade group were examined. SUVmax value of ISUP grade group 1 patients was slightly higher compared with that of positive BPH, but the difference was not significant. SUVmax was weak in discriminating BPH from PCa in all ISUP grade groups. Considering that SUVmax positively correlated with ISUP grade group (rspearman = 0.4093, P = 0.0004), and ISUP grade group 2 patients had a higher SUVmax value than ISUP grade group 1 patients, we further evaluated the ability of SUVmax to discriminating clinically insignificant PCa and positive BPH from clinically significant PCa by adding positive BPH patients to ISUP grade group 1. The analysis showed that the SUVmax value of ISUP grade group 2 was significantly higher than that of the mixed group. It preliminarily indicated the potential of SUVmax in distinguishing clinically insignificant PCa and positive BPH. SUVmax could effectively distinguish BPH and ISUP grade group 1 patients with an AUC of 0.8562, the optimal SUVmax cutoff value was 9.750 with a sensitivity of 64.71% and a specificity of 97.22%. Considering the importance of specificity in biopsy-free RP, the optimal SUVmax cutoff value with 100% specificity was 14.60, with a sensitivity of 41.18% (95% CI, 31.32% to 51.80%) and a specificity of 100% (95% CI, 90.36% to 100%).
Conclusions: To summarize, our results present, for the first time, the BPH-related false positive rate of 68Ga-PSMA PET/CT in the primary diagnosis of PCa. Using SUVmax values in biopsy-free RP can effectively exclude both BPH and ISUP grade group 1 patients.
In this issue
Jump to section
Related Articles
Cited By...
- No citing articles found.