Prostate-specific membrane antigen positron emission tomography in addition to multiparametric magnetic resonance imaging and biopsies to select prostate cancer patients for focal therapy

Abstract

Objective: To evaluate the additional value of prostate-specific membrane antigen positron emission tomography (PSMA-PET) to conventional diagnostic tools to select patients for hemi-ablative focal therapy (FT).

Patients and methods: We performed a retrospective analysis on a multicentre cohort (private and institutional) of 138 patients who underwent multiparametric magnetic resonance imaging (mpMRI), PSMA-PET, and systematic biopsies prior to radical prostatectomy between January 2011 and July 2021. Patients were eligible when they met the consensus criteria for FT: PSA <15 ng/mL, clinical/radiological T stage ≤T2b, and International Society of Urological Pathology (ISUP) grade 2-3. Clinically significant prostate cancer (csPCa) was defined as ISUP grade ≥2, extracapsular extension >0.5 mm or seminal vesicle involvement at final histopathology. The diagnostic accuracy of mpMRI, systematic biopsies and PSMA-PET for csPCa (separate and combined) was calculated within a four-quadrant prostate model by receiver-operating characteristic and 2 × 2 contingency analysis. Additionally, we assessed whether the diagnostic tools correctly identified patients suitable for hemi-ablative FT.

Results: In total 552 prostate quadrants were analysed and 272 (49%) contained csPCa on final histopathology. The area under the curve, sensitivity, specificity, positive predictive value and negative predictive value for csPCa were 0.79, 75%, 83%, 81% and 77%, respectively, for combined mpMRI and systematic biopsies, and improved after addition of PSMA-PET to 0.84, 87%, 80%, 81% and 86%, respectively (P < 0.001). On final histopathology 46/138 patients (33%) were not suitable for hemi-ablative FT. Addition of PSMA-PET correctly identified 26/46 (57%) non-suitable patients and resulted in 4/138 (3%) false-positive exclusions.

Conclusions: Addition of PSMA-PET to the conventional work-up by mpMRI and systematic biopsies could improve selection for hemi-ablative FT and guide exclusion of patients for whom whole-gland treatments might be a more suitable treatment option.

Keywords: PSMA‐PET; biopsy; focal therapy; mpMRI; prostate cancer.