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.