RESULTS
Clinical and pathological features of the patients are summarised in Table 2. A total of 64 patients were included in the study. All patients underwent both mpMRI and 68Ga-PSMA PET/MRI. In eight patients, no lesion was observed in the mpMRI, and in eight patients, no pathological uptake was observed in the 68Ga-PSMA PET/MRI. In one patient, neither lesion nor pathological uptake was observed in imaging.
Correlation analyses were performed between lesion length and lesion volume and between PSAD and SUVmax. A strong correlation was found between lesion length and lesion volume, while there was a moderate correlation between PSAD and SUVmax(rs = 0.66, p < 0.001; rs = 0.32, p < 0.001, respectively). Regarding the agreement between mpMRI and 68Ga-PSMA PET/MRI in identifying the index tumour, the Cohen’s kappa coefficient (κ) was 0.505 ± 0.56, indicating moderate agreement.
The sensitivity, specificity, PPV, NPV, PLR, NLR, and the accuracy of mpMRI, 68(Ga)-PSMA PET/MRI, and combined imaging are shown in Table 3. Combined imaging had significantly higher diagnostic accuracy compared with mpMRI and 68Ga-PSMA PET/MRI (change in AUC: 0.084 and 0.046, p < 0.001 and p = 0.028, respectively), while no statistically significant difference was found between mpMRI and 68(Ga)-PSMA PET/MRI (change in AUC: 0.38, p = 0.246) (Fig. 2). Moreover, 68Ga-PSMA PET/MRI has higher sensitivity and specificity rates compared with mpMRI. However, no statistically significant difference was found (p = 0.464).
Patients were separated into two groups according to the tumour pathology (ISUP < 3 and ISUP ≥ 3), and then the cut-off values of SUVmax, total PSA, PSAD, lesion length, and lesion volume were determined at points with optimal specificity and sensitivity via ROC curves generated in predicting advanced tumour ISUP grade. Optimal cut-off values were found to be 10 ng/ml for total PSA (AUC [CI 95%] = 0.64 [0.50–0.78]), 0.18 ng/ml/ml for PSAD (AUC [CI 95%] = 0.67 [0.54–0.80]), 1.5 ml for lesion volume (AUC [CI 95%] = 0.69 [0.55–0.83]), 15 mm for lesion length (AUC [CI 95%] = 0.70 [0.56–0.84]), and 7.1 for SUVmax (AUC [CI 95%] = 0.70 [0.57–0.83]).
The sensitivity and specificity of mpMRI, 68Ga-PSMA PET/MRI and combined imaging according to the subgroups of total PSA, PSAD, lesion length, lesion volume, and SUVmax are shown in Table 4. It was seen that the sensitivity of the mpMRI and68Ga-PSMA PET/MRI in the high total PSA, high PSAD, high PI-RADS score, high lesion length, and high lesion volume groups increased. The specificity of mpMRI was also increased in the high total PSA and high PSAD groups. The sensitivity of 68Ga-PSMA PET/MRI also increased in the high SUVmax group. In the ROC analysis performed by evaluating AUC changes for all imaging methods, no significant difference was found between any subgroups in terms of diagnostic accuracy.