PET/MRI in Prostate Cancer: A Systematic Review and Meta-Analysis

The aim of our study was to summarize the diagnostic information provided by PET/MRI imaging in patients with prostate cancer, being a technique able to explore combined metabolic/receptorial, anatomical, and functional imaging. We performed a systematic review and meta-analysis of the literature using medical subject heading (MeSH) words “choline” or “PSMA” and “prostate cancer” or “prostate” and “PET/MRI” or “PET MRI” or “PET-MRI” or “positron emission tomography/magnetic resonance imaging, and exploring three databases such as PubMed, Scopus, and Web of Science. Inclusion criteria were studies with a sample size >10 patients and enough data to prepare a 2 x 2 contingency table. The quality assessment of the selected studies was performed using QUADAS-2 criteria and the analysis was made with appropriate software (i.e. Meta-DiSc® version 1.4 and Comprehensive Meta-Analysis software version 3.3.070). After identification screening, we finally included 50 articles for the qualitative analysis and 23 for the quantitative assessment. The pooled data concerned 2059 patients undergoing PET/MRI for prostate cancer. Initial disease staging was the main indication in 24 studies, followed by restaging and staging plus restaging. Radiolabeled PSMA was the most used radiopharmaceutical agent.

In staging, PET/MRI showed a high pooled sensitivity for the detection of primary cancer in the prostate gland, mainly at patient-based analysis. In one study, extracapsular spread of prostate cancer was detected better with 68Ga-PSMA PET/MRI than with mpMRI. In another study, PET and PET/MRI produced a considerably lower proportion of equivocal results (i.e. PIRADS 3) than mpMRI. The pooled sensitivity for lymph-node metastasis was about 65% (Table 1).

In the biochemical recurrence setting, PET/MRI reported a detection rate ranging between 54.5% and 97%. The detection rate was higher in accordance with PSA levels. The pooled detection rate was 81%. It was higher for studies using radiolabelled PSMA than choline (82 vs. 77 %, respectively). In the studies that compared PET/CT with PET/MRI in the same population, the pooled detection rates were similar. However, in some studies, PET/MRI was superior to PET/CT in detecting primary prostate malignant lesions, particularly in cases of local recurrence with low prostate-specific antigen (PSA) levels (Table 2). Furthermore, PET/MRI achieved a slightly higher detection rate in recurrent lymph-node disease. Finally, the detection rate of bone metastasis was comparable between PET/CT and PET/MRI in the case of PSA <2 ng/ml, but PET/CT performed better with PSA levels > 2 ng/ml. This result suggests the implementation of specific bone sequences in PET/MRI.

Table 1. Pooled sensitivity and specificity for staging

Pooled sensitivity and specificity for staging

Table 2. Pooled detection rate in restaging

Finally, therapeutic strategies were modified in at least 30% of patients in staging, while it prompted changes in up to 75% of cases in restaging, for example by identifying oligometastatic disease and thus guiding to the appropriate radiotherapeutic planning.

Written by: Laura Evangelista, Fabio Zattoni, Gianluca Cassarino, Paolo Artioli, Diego Cecchin, Fabrizio Dal Moro, Pietro Zucchetta

Nuclear Medicine Unit, Department of Medicine, Padova University Hospital, Via Giustiniani 2, Padova, Italy., Urology Unit, Department of Medicine, Udine University Hospital, Udine, Italy., Nuclear Medicine Unit, Department of Medicine, Padova University Hospital, Via Giustiniani 2, Padova, Italy.

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