Abstract
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Introduction: Role of mpMRI vs Ga-68 PSMA PET/ CT Scan in the detection of prostate cancer.
Aim: To check the diagnostic accuracy of multiparametric MRI (mpMRI) and gallium 68 (68 Ga)-labelled prostate specific membrane antigen (PSMA)-11 PET/CT scan in the diagnosis of prostate cancer. Materials and Methods: In this prospective of men (n= 34) with biopsy-proven prostate cancer underwent simultaneous mpMRI and Ga-68 PSMA PET Scan between December 2016 to November 2018. The pathological specimens obtained by MRI fusion biopsy were processed and final histopathology was used as reference standard and correlated with the imaging findings. For the purpose of analysis, the prostate was arbitrarily divided into 12 unique sectors (total 408 sectors in 34 patients) and total 371 positive cancer regions were compared for PET/MRI and multiparametric. Prostate mpMRI examinations were performed on a closed superconducting 3T MRI system (Ingenia 3T, Philips, Amsterdam, Netherlands) using an external phased array body coil. Prostate Imaging Reporting and Data system (PIRAD V2) scoring was performed in all patients were compared with Gleason score.
Results: mpMRI and Ga68 PSMA PET/CT data from 34 patients (median age, 65.5 years; interquartile range: 45 years to 78 years) were evaluated. The PSA value of the study population ranged from 10.067 ng/ml to 161.583 ng/ml with the mean of 30.333 ng/ml (standard deviation - 26.236). Among the 408 sectors, 371 sectors (44.81 %) were positive for cancer on histopathology and 324 sectors were positive for clinically significant prostate cancer (38.13%) having Gleason score >7. The region-specific sensitivities of 68Ga PSMA PET/CT showed overall sensitivity, specificity, PPV, and NPV of 82.1%, 68.2%, 80.5%, and 70.4% for detection of prostate cancer with the significant difference between the prostate cancer positive group and prostate cancer negative group (P value - <0.001). Among 157 sectors negative for prostate cancer, both mpMRI (PI-RADS ≥ 3) and PET were correctly negative in 77 sectors (49%), and both MRI (PI-RADS ≥ 3) and PET were wrongly positive in 20 sectors (12.7%). In 30 sectors (19.1%) negative for prostate cancer, mpMRI (PI-RADS ≥ 3) correctly showed it to be negative, when PET was wrongly positive. In 30 sectors (19.1%) negative for prostate cancer, PET correctly showed it to be negative, when mpMRI (PI-RADS ≥ 3) was wrongly positive. Among 196 sectors negative for clinically significant prostate cancer, both mpMRI (PI-RADS ≥ 3) and PET were correctly negative in 81 sectors (41.3%), and both MRI (PI-RADS ≥ 3) and PET were wrongly positive in 38 sectors (19.3%). In 31 sectors (15.8%) negative for clinically significant prostate cancer, mpMRI (PI-RADS≥ 3) correctly showed it to be negative, when PET was wrongly positive. In 46 sectors (23.4%) negative for clinically significant prostate cancer, PET correctly showed it to be negative, when mpMRI (PI-RADS ≥ 3) was wrongly positive.
Conclusions: Multiparametric MRI (using PI-RADS v2 cut off ≥3 scoring) (sensitivity - 97.5%) and 68 Ga PSMA PET CT (sensitivity - 88.2%) individually are reliable tools in the detection and localization of clinically significant prostate cancer. Combined use of 68Ga PSMA PET CT and multiparametric MRI in parallel (combined sensitivity - 99.7%), improves the sensitivity of detection of clinically significant prostate cancer.