Quantitative imaging parameters to predict the local staging of prostate cancer in intermediate- to high-risk patients

Objectives PSMA PET/MRI showed the potential to increase the sensitivity for extraprostatic disease (EPD) assessment over mpMRI; however, the interreader variability for EPD is still high. Therefore, we aimed to assess whether quantitative PSMA and mpMRI imaging parameters could yield a more robust EPD prediction. Methods We retrospectively evaluated PCa patients who underwent staging mpMRI and [Ga-68]PSMA-PET, followed by radical prostatectomy at our institution between 01.02.2016 and 31.07.2019. Fifty-eight cases with PET/MRI and 15 cases with PET/CT were identified. EPD was determined on histopathology and correlated with quantitative PSMA and mpMRI parameters assessed by two readers: ADC (mm(2)/1000 s), longest capsular contact (LCC, mm), tumor volume (cm(3)), PSMA-SUVmax and volume-based parameters using a fixed threshold at SUV > 4 to delineate PSMA(total) (g/ml) and PSMA(vol) (cm(3)). The t test was used to compare means, Pearson's test for categorical correlation, and ROC curve to determine the best cutoff. Interclass correlation (ICC) was performed for interreader agreement (95% CI). Results Seventy-three patients were included (64.5 +/- 6.0 years; PSA 14.4 +/- 17.1 ng/ml), and 31 had EPD (42.5%). From mpMRI, only LCC reached significance (p = 0.005), while both volume-based PET parameters PSMA(total) and PSMA(vol) were significantly associated with EPD (p = 0.008 and p = 0.004, respectively). On ROC analysis, LCC, PSMA(total), and PSMA(vol) reached an AUC of 0.712 (p = 0.002), 0.709 (p = 0.002), and 0.718 (p = 0.002), respectively. ICC was moderate-good for LCC 0.727 (0.565-0.828) and excellent for PSMA(total) and PSMA(vol) with 0.944 (0.990-0.996) and 0.985 (0.976-0.991), respectively. Conclusions Quantitative PSMA parameters have a similar potential as mpMRI LCC to predict EPD of PCa, with a significantly higher interreader agreement.