Prostate cancer is the most common malignancy in men in Australia, [1] but there is currently no concurrent literature on the percentage of multizonal prostate malignancy. Multiparametric MRI (MRIp) and PSMA PET are key imaging modalities in prostate cancer workup. The accuracy of MRI in grading prostate cancer may vary based on lesion characteristics, particularly zonal extent. This study evaluates how lesions spanning multiple prostate zones influence MRI accuracy compared to PSMA PET, using matched biopsy and radical prostatectomy (RP) data.

We conducted a prospective analysis of 56 patients who underwent multiparametric MRI (MRIp), PSMA PET, and radical prostatectomy (RP). Lesions were mapped according to prostate zones—peripheral (PZ), transition (TZ), anterior (AZ), or multi-zonal—based on imaging and histopathology. Cross-zonal involvement was defined as lesions spanning two or more anatomical zones. MRI and PSMA PET accuracy were assessed by comparing imaging-assigned ISUP grades and lesion localization with final RP pathology. Accuracy was categorized as complete, partial, or inaccurate. Subgroup analysis examined how multi-zonal involvement influences diagnostic concordance between imaging modalities and RP outcomes. Few studies focus on combined MRI and PSMA PET accuracy [2,3], but do not focus on multizonal parameters and its effect on accuracy.

Data from 56 patients, with a median age of 67, were analyzed. Of these, 23 patients (41.1%) had lesions with multi-zonal involvement, most commonly spanning the peripheral (PZ) and anterior (AZ) zones. MRIp was fully accurate in 26 cases (46.4%), partially accurate in 30 (53.6%), and completely inaccurate in 6 (10.7%). In contrast, PSMA PET was fully accurate in 41 cases (73.2%), partially accurate in 18 (32.1%), and inaccurate in 3 (5.4%). In multi-zonal lesions, MRIp accuracy dropped significantly (p = 0.018), with underestimation observed in 56.5% of these cases. PSMA PET maintained greater accuracy in this group (78.3% accurate, p = 0.007). The odds ratio for PSMA PET providing correct assessment compared to MRIp in multi-zonal disease was 2.9 (95% CI: 1.1–7.4), indicating nearly triple the likelihood of accurate grading. These results support the integration of PSMA PET with MRIp, particularly in complex multi-zonal disease presentations.

Lesions with multi-zonal involvement significantly reduce the grading accuracy of MRI, particularly due to challenges in visualizing anterior and transitional zone components. PSMA PET demonstrates more consistent accuracy across all zones, reinforcing the value of a multimodal imaging approach for comprehensive prostate cancer assessment.